Getting to Grips with Surveillance

Getting to Grips with Surveillance
Flight Operations Support & Services
AIRBUS S.A.S.
31707 BLAGNAC CEDEX, FRANCE
CONCEPT DESIGN GDB
MAY 2009
PRINTED IN FRANCE
© AIRBUS S.A.S. 2009
ALL RIGHTS RESERVED
AIRBUS, ITS LOGO, A300, A310, A318,
A319, A320, A321, A330, A340, A350, A380,
A400M ARE REGISTERED TRADEMARKS
getting to grips with
Proprietary document.
By taking delivery of this Brochure (hereafter “Brochure”), you
accept on behalf of your company to comply with the following: .No
other property rights are granted by the delivery of this Brochure
than the right to read it, for the sole purpose of information. This
Brochure, its content, illustrations and photos shall not be modified
nor reproduced without prior written consent of Airbus S.A.S. This
Brochure and the materials it contains shall not, in whole or in part,
be sold, rented, or licensed to any third party subject to payment or
not. This Brochure may contain market-sensitive or other information that is correct at the time of going to press. This information
involves a number of factors which could change over time, affecting the true public representation. Airbus assumes no obligation to
update any information contained in this document or with respect
to the information described herein. The statements made herein do
not constitute an offer or form part of any contract. They are based
on Airbus information and are expressed in good faith but no warranty or representation is given as to their accuracy. When additional information is required, Airbus S.A.S can be contacted to provide
further details. Airbus S.A.S shall assume no liability for any damage in connection with the use of this Brochure and the materials it
contains, even if Airbus S.A.S has been advised of the likelihood of
such damages. This licence is governed by French law and exclusive jurisdiction is given to the courts and tribunals of Toulouse
(France) without prejudice to the right of Airbus to bring proceedings
for infringement of copyright or any other intellectual property right
in any other court of competent jurisdiction.
surveillance
Issue I - May 2009
Flight Operations Support & Services
Customer Services
1, rond-point Maurice Bellonte, BP 33
31707 BLAGNAC Cedex FRANCE
Telephone +33 (0)5 61 93 33 33
getting to grips with
surveillance
Getting to grips with Surveillance
Foreword
FOREWORD
The present brochure describes the surveillance in the broad sense of the term,
from an airborne system perspective. It covers existing systems (e.g.
transponder, TCAS, TAWS, etc) as well as emerging systems (e.g. AESS, ATSAW,
etc) and new technologies (e.g. ADS-B).
The present brochure provides supplementary information to existing Flight
Operations documents (CBT, FCOM, FCTM, FOBN). Therefore, the present
brochure intentionally limits the set of recommendations. Please refer to existing
Flight Operations documents for the complete set of recommendations.
The contents of this Getting to Grips brochure are not subject to Airworthiness
Authority approval. Therefore, this brochure neither supersedes the requirements
mandated by the State in which the operator’s aircraft is registered, nor does it
supersede the contents of other approved documentation (e.g. AFM, MEL, etc). If
any contradiction exists between this brochure and local/national authority
regulations (or other approved documentation), the latter applies.
While AIRBUS SAS has taken every precaution to avoid any errors or
omissions that may inadvertently be contained in this brochure, AIRBUS
SAS does not accept any liability for the accuracy of information contained
herein. Please refer to the relevant manufacturer publications to verify
information.
AIRBUS SAS is the first aeronautical company to get the ISO 14001 certification for
its Environmental Management System. The electronic distribution of this document
is part of the AIRBUS SAS environmental commitments. In its efforts to alleviate
the ecological footprint of aviation industries, AIRBUS SAS warmly invites readers
to print this document only if necessary. The optimal print-out settings should
be: printing of desired pages only, use of recycled paper, toner saving
switched to on, color options to black and white, printing layout set to 2
pages per sheet, front and back. AIRBUS SAS thanks you for your cooperation.
Any questions with respect to information contained herein should be directed to:
AIRBUS SAS
Flight Operations Support & Services
Customer Services Directorate
1, Rond Point Maurice Bellonte, BP 33
31707 BLAGNAC Cedex – FRANCE
Fax: 33 5 61 93 29 68 or 33 5 61 93 44 65
E-mail: [email protected]
-1-
Table of contents
Getting to grips with Surveillance
TABLE OF RECORDS
Issue
Date
Chapter
Issue 1
May 2009
All
Main Changes
First edition
TABLE OF CONTENTS
EXECUTIVE SUMMARY .................................................................................................... 12
ABBREVIATIONS .............................................................................................................. 20
REFERENCES....................................................................................................................... 25
AIRBUS REFERENCES...................................................................................................... 28
1.
INTRODUCTION............................................................................................. 1-1
1.1.
1.1.1.
1.1.2.
What is Surveillance? ........................................................................ 1-2
Surveillance from the Flight Crew’s Perspective................................ 1-2
Surveillance from the Air Traffic Controller’s Perspective ................. 1-3
1.2.
1.2.1.
1.2.2.
1.2.3.
How to Read the Brochure? ............................................................... 1-3
Surveillance Systems and Functions.................................................. 1-3
Chapter Structure.............................................................................. 1-4
Captions ............................................................................................ 1-4
1.3.
System Summary .............................................................................. 1-5
2.
AIRCRAFT IDENTIFICATION AND POSITION REPORTING........... 2-1
2.1.
2.1.1.
2.1.2.
2.1.3.
2.1.3.1.
2.1.3.2.
2.1.3.3.
2.1.3.4.
2.1.3.5.
2.1.3.6.
2.1.3.7.
2.1.3.8.
2.1.3.9.
2.1.4.
Description of Transponder ............................................................... 2-3
Mode A .............................................................................................. 2-4
Mode C .............................................................................................. 2-4
Mode S .............................................................................................. 2-4
Mode S Data Link ................................................................................ 2-5
Elementary Surveillance (ELS) .............................................................. 2-5
Enhanced Surveillance (EHS) ................................................................ 2-5
Ground Initiated Comm B (GCIB) .......................................................... 2-6
COMM A and COMM B .......................................................................... 2-6
24-bit Address or Mode S Address ......................................................... 2-6
Automatic Dependent Surveillance – Broadcast (ADS-B) ........................... 2-6
Extended Squitter ............................................................................... 2-7
1090 Extended Squitter........................................................................ 2-7
Transponder Controls ........................................................................ 2-8
-2-
Getting to grips with Surveillance
2.2.
2.2.1.
2.2.2.
2.2.3.
2.2.4.
2.2.5.
2.2.6.
2.2.7.
2.2.8.
2.2.9.
2.2.10.
2.2.11.
2.2.12.
2.2.13.
2.2.14.
2.2.15.
2.2.16.
2.2.17.
Table of contents
Aircraft Identification and Position Reporting with ADS-B ................ 2-8
ADS-B Surveillance in Non-Radar Areas (ADS-B NRA)....................... 2-9
ADS-B surveillance in Radar Areas (ADS-B RAD)............................. 2-10
ADS-B Surveillance on Airport Surfaces (ADS-B APT)...................... 2-10
Generic Emergency Indicator .......................................................... 2-11
Discrete Emergency Codes .............................................................. 2-11
DO-260 and DO-260A ...................................................................... 2-11
Geographical Filtering of SQWK Code .............................................. 2-12
Version Number .............................................................................. 2-12
Receiver Autonomous Integrity Monitoring (RAIM) / Fault Detection
and Exclusion (FDE) ........................................................................ 2-12
GPS Horizontal Figure of Merit (HFOM) ........................................... 2-13
GPS Horizontal Protection Limit (HPL) ............................................ 2-13
Selective Availability (SA) ............................................................... 2-13
Navigational Uncertainty Category (NUC) ....................................... 2-14
Navigation Integrity Category (NIC) ............................................... 2-14
Navigational Accuracy Category (NAC)............................................ 2-14
Surveillance Integrity Level (SIL) ................................................... 2-14
ADS-B Controls and Indications....................................................... 2-15
2.3.
Aircraft Identification and Position Reporting with Wide Area
Multilateration ................................................................................................ 2-15
2.4.
Aircraft identification and Position Reporting with FANS................. 2-17
2.5.
2.5.1.
2.5.1.1.
2.5.1.2.
2.5.2.
2.5.2.1.
2.5.2.2.
Operational Recommendations for Transponder.............................. 2-17
Conventional Transponder Operations ............................................ 2-17
For the Airline ................................................................................... 2-17
For the Flight Crew ............................................................................ 2-18
ADS-B Operations............................................................................ 2-18
For the Airline ................................................................................... 2-18
For the Flight Crew ............................................................................ 2-18
2.6.
2.6.1.
2.6.2.
Regulations for Transponder ........................................................... 2-19
Carriage of Transponder.................................................................. 2-19
Operational Approval of ADS-B OUT ................................................ 2-20
2.7.
2.7.1.
2.7.2.
2.7.3.
2.7.4.
Manufacturers for Transponder ....................................................... 2-21
ACSS XS 950.................................................................................... 2-22
Transponder Part of ACSS T3CAS .................................................... 2-22
Rockwell Collins TPR 901 ................................................................ 2-22
Honeywell TRA 67A ......................................................................... 2-22
2.8.
Future Systems ............................................................................... 2-22
3.
TRAFFIC SURVEILLANCE............................................................................ 3-1
3.1.
3.1.1.
3.1.2.
3.1.2.1.
3.1.2.2.
3.1.3.
3.1.3.1.
Description of ACAS – TCAS............................................................... 3-3
TCAS Designation .............................................................................. 3-4
TCAS Principle ................................................................................... 3-4
Detection Phase .................................................................................. 3-5
Tracking Phase ................................................................................... 3-6
TCAS and Mode S............................................................................... 3-6
Coordinated Maneuvers........................................................................ 3-6
-3-
Table of contents
Getting to grips with Surveillance
3.1.3.2.
3.1.4.
3.1.4.1.
3.1.4.2.
3.1.5.
3.1.6.
3.1.6.1.
3.1.6.2.
3.1.7.
3.1.7.1.
3.1.7.2.
3.1.8.
Communication with ATC Ground Stations .............................................. 3-7
Collision Threat Evaluation ................................................................ 3-7
Vertical Separation .............................................................................. 3-8
Time to Intercept (TAU) ....................................................................... 3-8
TCAS Envelopes ................................................................................. 3-9
TCAS II Change 7.1 ......................................................................... 3-10
CP112E – Solution to the Reversal Logic Issue....................................... 3-10
CP115 – Solution to the “ADJUST VERTICAL SPEED, ADJUST” Issue.......... 3-11
TCAS Indications ............................................................................. 3-12
TCAS Display .................................................................................... 3-12
TCAS Aural Alerts .............................................................................. 3-14
TCAS Controls.................................................................................. 3-17
3.2.
3.2.1.
3.2.2.
Operational Recommendations for TCAS ......................................... 3-18
For the Airline ................................................................................. 3-18
For the Flight Crew .......................................................................... 3-19
3.3.
Regulations for TCAS ....................................................................... 3-19
3.4.
3.4.1.
3.4.2.
3.4.3.
3.4.4.
Manufacturers for TCAS................................................................... 3-20
ACSS TCAS 2000 and T2CAS ............................................................ 3-20
TCAS Part of ACSS T3CAS ................................................................ 3-21
Rockwell Collins TTR 921................................................................. 3-21
Honeywell TPA 100A ....................................................................... 3-21
3.5.
Future Systems ............................................................................... 3-21
3.6.
3.6.1.
3.6.2.
3.6.2.1.
3.6.2.2.
3.6.2.3.
3.6.2.4.
3.6.3.
3.6.3.1.
3.6.3.2.
3.6.4.
3.6.4.1.
3.6.4.2.
3.6.5.
3.6.5.1.
3.6.5.2.
Description of ATSAW...................................................................... 3-23
Enriched Traffic Information ........................................................... 3-24
ATSAW Applications ........................................................................ 3-25
On Ground: ATSA Surface (ATSA SURF) ............................................... 3-25
In Flight: ATSA Airborne (ATSA AIRB) .................................................. 3-25
In Cruise: ATSA In Trail Procedure (ATSA ITP)....................................... 3-27
During Approach: ATSA Visual Separation on Approach (ATSA VSA) ......... 3-28
ATSAW Envelopes and Filtering Logic.............................................. 3-29
ATSAW Envelopes ............................................................................. 3-29
Filtering Logic ................................................................................... 3-29
ATSAW Indications .......................................................................... 3-29
ND .................................................................................................. 3-29
MCDU .............................................................................................. 3-32
ATSAW Controls .............................................................................. 3-38
MCDU controls .................................................................................. 3-38
Traffic Selector ................................................................................. 3-39
3.7.
3.7.1.
3.7.2.
Operational Recommendations for ATSAW ...................................... 3-40
For the Airline ................................................................................. 3-40
For the Flight Crew .......................................................................... 3-40
3.8.
Regulations for ATSAW.................................................................... 3-40
3.9.
Manufacturer for ATSAW ................................................................. 3-40
3.10.
3.10.1.
Future Applications ......................................................................... 3-41
ATSA SURF with OANS..................................................................... 3-41
-4-
Getting to grips with Surveillance
Table of contents
3.10.2.
Enhanced Sequencing and Merging Operations ............................... 3-41
4.
TERRAIN SURVEILLANCE........................................................................... 4-1
4.1.
4.1.1.
4.1.1.1.
4.1.1.2.
4.1.1.3.
4.1.1.4.
4.1.2.
4.1.2.1.
4.1.3.
4.1.3.1.
4.1.3.2.
4.1.3.3.
4.1.4.
4.1.4.1.
4.1.4.2.
4.1.5.
4.1.5.1.
4.1.5.2.
4.1.5.3.
4.1.5.4.
4.1.5.5.
4.1.6.
4.1.6.1.
4.1.6.2.
Description of TAWS.......................................................................... 4-2
TAWS Principles ................................................................................ 4-2
Terrain Database................................................................................. 4-3
Obstacle Database............................................................................... 4-4
Runway Database................................................................................ 4-4
Aircraft Performance Database .............................................................. 4-4
Reactive (basic) TAWS Functions ...................................................... 4-5
EGPWS Mode 6: Excessive Bank Angle ................................................... 4-7
Predictive TAWS Functions ................................................................ 4-7
Enhanced GPWS Functions.................................................................... 4-8
Predictive T2CAS Functions................................................................. 4-10
EGPWS/T2CAS Comparison................................................................. 4-14
Introduction of GPS Position into TAWS Architecture...................... 4-15
EGPWS Geometric Altitude – T2CAS CPA Altitude ................................... 4-16
Use of GPS for Lateral Positioning ........................................................ 4-16
TAWS Indications ............................................................................ 4-18
TAWS Basic Mode Indications.............................................................. 4-18
TAWS Predictive Functions.................................................................. 4-18
EGPWS: Obstacle .............................................................................. 4-20
EGPWS: Peaks Mode.......................................................................... 4-20
Terrain Display in Polar Areas.............................................................. 4-21
TAWS Controls................................................................................. 4-22
A300/A310 Controls .......................................................................... 4-22
A320/A330/A340 Controls .................................................................. 4-22
4.2.
4.2.1.
4.2.2.
Operational Recommendations for TAWS ........................................ 4-23
For the Airline ................................................................................. 4-23
For the Flight Crew .......................................................................... 4-24
4.3.
Regulations for TAWS...................................................................... 4-24
4.4.
4.4.1.
4.4.2.
4.4.3.
Manufacturers for TAWS.................................................................. 4-25
Honeywell EGPWS ........................................................................... 4-25
ACSS T2CAS..................................................................................... 4-25
TAWS Module of ACSS T3CAS .......................................................... 4-26
4.5.
Future Systems ............................................................................... 4-26
5.
RUNWAY SURVEILLANCE........................................................................... 5-1
5.1.
5.1.1.
5.1.1.1.
5.1.1.2.
5.1.1.3.
5.1.1.4.
5.1.1.5.
5.1.1.6.
5.1.1.7.
Description of OANS .......................................................................... 5-4
OANS Terminology ............................................................................ 5-4
Airport Mapping Data Base (AMDB)........................................................ 5-4
Airport Data Base (ADB)....................................................................... 5-4
Airport Map ........................................................................................ 5-4
Coverage Volume ................................................................................ 5-5
Airport Map Displayed in ARC and ROSE NAV Mode .................................. 5-5
Airport Map Displayed in PLAN Mode ...................................................... 5-5
Map Reference Point ............................................................................ 5-5
-5-
Table of contents
Getting to grips with Surveillance
5.1.2.
5.1.2.1.
5.1.2.2.
5.1.3.
5.1.3.1.
5.1.3.2.
5.1.3.3.
5.1.3.4.
5.1.3.5.
5.1.3.6.
5.1.4.
5.1.4.1.
5.1.4.2.
5.1.4.3.
5.1.4.4.
5.1.4.5.
5.1.4.6.
OANS Principles................................................................................. 5-5
Airport Moving Map ............................................................................. 5-5
Approaching Runway Advisory............................................................... 5-6
OANS Indications .............................................................................. 5-7
Aircraft Symbol ................................................................................... 5-8
FMS Active Runway ............................................................................. 5-8
FMS Destination Arrow ......................................................................... 5-9
Airport Map ........................................................................................ 5-9
Approaching Runway Indication........................................................... 5-11
OANS Messages ................................................................................ 5-12
OANS Controls ................................................................................. 5-13
EFIS CP Range Selector...................................................................... 5-13
EFIS CP ND Display Mode ................................................................... 5-13
KCCU .............................................................................................. 5-15
MOVE Function.................................................................................. 5-15
Interactive Control Menu .................................................................... 5-15
Soft Control Panel ............................................................................. 5-15
5.2.
5.2.1.
5.2.2.
Operational Recommendations for OANS ........................................ 5-16
For the Airline ................................................................................. 5-16
For the Flight Crew .......................................................................... 5-17
5.3.
Regulations for OANS ...................................................................... 5-17
5.4.
5.4.1.
Manufacturer for OANS.................................................................... 5-17
Update of OANS Databases.............................................................. 5-18
5.5.
Future Systems ............................................................................... 5-18
5.6.
5.6.1.
5.6.1.1.
5.6.1.2.
5.6.1.3.
5.6.1.4.
5.6.1.5.
5.6.2.
5.6.3.
5.6.3.1.
5.6.3.2.
5.6.3.3.
5.6.3.4.
5.6.4.
5.6.5.
5.6.5.1.
Description of ROW/ROP................................................................. 5-20
ROW/ROP Principles ....................................................................... 5-21
Automatic Detection of the Runway for Landing ..................................... 5-22
ROW Armed ..................................................................................... 5-22
ROW Engaged................................................................................... 5-22
ROP Armed....................................................................................... 5-23
ROP Engaged.................................................................................... 5-23
Auto Brake Disconnection ............................................................... 5-23
ROW/ROP Indications ..................................................................... 5-24
ROW Indications When Armed............................................................. 5-24
ROW Indications When Engaged .......................................................... 5-24
ROP Indications When Armed .............................................................. 5-26
ROP Indications When Engaged ........................................................... 5-26
Indications for Auto Brake Disconnection ....................................... 5-27
ROW/ROP Controls.......................................................................... 5-27
Runway Shift .................................................................................... 5-27
5.7.
5.7.1.
5.7.2.
Operational recommendations for ROW/ROP .................................. 5-28
For the airline.................................................................................. 5-28
For the flight crew ........................................................................... 5-28
5.8.
Regulations for ROW/ROP............................................................... 5-28
5.9.
Manufacturers for ROW/ROP/BTV................................................... 5-29
-6-
Getting to grips with Surveillance
Table of contents
5.10.
Future systems................................................................................ 5-29
5.11.
5.11.1.
5.11.1.1.
5.11.1.2.
5.11.2.
5.11.2.1.
5.11.2.2.
5.11.3.
5.11.3.1.
5.11.3.2.
Description of RAAS ........................................................................ 5-31
Approaching Runway – On Ground Advisory – Routine ................... 5-31
Purpose .......................................................................................... 5-31
Triggering Conditions ........................................................................ 5-31
On Runway Advisory – Routine ....................................................... 5-32
Purpose .......................................................................................... 5-32
Triggering Conditions ........................................................................ 5-32
Takeoff on Taxiway Advisory – Non-Routine ................................... 5-32
Purpose .......................................................................................... 5-32
Triggering Conditions ........................................................................ 5-32
5.12.
Operational Recommendations for RAAS ......................................... 5-33
5.13.
Regulations for RAAS ...................................................................... 5-33
5.14.
Manufacturer for RAAS .................................................................... 5-33
5.15.
Future Systems ............................................................................... 5-33
6.
WEATHER SURVEILLANCE ......................................................................... 6-1
6.1.
6.1.1.
6.1.1.1.
6.1.1.2.
6.1.1.3.
6.1.1.4.
6.1.1.5.
6.1.1.6.
6.1.1.7.
6.1.1.8.
6.1.2.
6.1.2.1.
6.1.2.2.
6.1.3.
6.1.3.1.
6.1.3.2.
6.1.3.3.
6.1.3.4.
6.1.4.
6.1.5.
6.1.5.1.
6.1.5.2.
6.1.5.3.
6.1.5.4.
6.1.5.5.
6.1.6.
6.1.7.
6.1.7.1.
6.1.7.2.
6.1.8.
Description of Weather Radar ........................................................... 6-3
Radar Theory..................................................................................... 6-3
Reflectivity of Water Molecules .............................................................. 6-3
Reflectivity of Thunderstorms................................................................ 6-4
Frequency Band .................................................................................. 6-5
Gain .................................................................................................. 6-5
Antenna ............................................................................................. 6-6
Radar Beam ....................................................................................... 6-7
Interfering Radio Transmitters............................................................. 6-11
Radiation Hazards ............................................................................. 6-11
Weather, Turbulence and Wind Shear Detection ............................. 6-12
Coverage ......................................................................................... 6-12
Wind Shear Detection ........................................................................ 6-13
Weather Radar Operating Modes ..................................................... 6-13
WX Mode ......................................................................................... 6-13
WX+T, WX/TURB or TURB Mode .......................................................... 6-13
MAP Mode ........................................................................................ 6-14
PWS Mode........................................................................................ 6-14
Reactive Wind Shear ....................................................................... 6-16
Weather Radar Functions per Manufacturer .................................... 6-16
Autotilt (Honeywell)........................................................................... 6-17
Multiscan (Rockwell Collins) ................................................................ 6-18
Ground Clutter Suppression – GCS (Rockwell Collins) ............................. 6-19
Long Range Color Enhancement (Rockwell Collins) ................................. 6-20
GAIN PLUS (Rockwell Collins).............................................................. 6-20
Reactive Wind Shear Indications ..................................................... 6-23
Weather Radar Indications.............................................................. 6-23
Weather Radar Messages ................................................................... 6-25
Wind Shear Indications ...................................................................... 6-25
Weather Radar Controls .................................................................. 6-26
-7-
Table of contents
Getting to grips with Surveillance
6.2.
6.2.1.
6.2.1.1.
6.2.1.2.
6.2.2.
6.2.2.1.
6.2.2.2.
Operational Recommendations for Weather Radar .......................... 6-27
Weather Radar Operations .............................................................. 6-27
For the Airline ................................................................................... 6-27
For the Flight Crew ............................................................................ 6-27
Wind Shear...................................................................................... 6-28
For the Airline ................................................................................... 6-28
For the Flight Crew ............................................................................ 6-28
6.3.
Regulations for Weather Radar ....................................................... 6-29
6.4.
6.4.1.
6.4.2.
Manufacturers for Weather Radar ................................................... 6-31
Honeywell RDR-4B .......................................................................... 6-31
Rockwell Collins WXR 701X and WXR 2100 ..................................... 6-31
6.5.
6.5.1.
Future Systems ............................................................................... 6-32
Honeywell RDR 4000 ....................................................................... 6-32
7.
AIRCRAFT ENVIRONMENT SURVEILLANCE......................................... 7-1
7.1.
7.1.1.
7.1.2.
7.1.2.1.
7.1.2.2.
7.1.2.3.
7.1.3.
7.1.3.1.
7.1.3.2.
7.1.3.3.
7.1.4.
7.1.4.1.
7.1.4.2.
7.1.4.3.
7.1.4.4.
7.1.5.
7.1.6.
7.1.7.
7.1.7.1.
7.1.7.2.
7.1.7.3.
7.1.8.
7.1.8.1.
7.1.8.2.
7.1.8.3.
7.1.8.4.
7.1.9.
7.1.9.1.
7.1.9.2.
7.1.9.3.
7.1.9.4.
7.1.9.5.
Description of AESS ........................................................................... 7-3
Integration of Surveillance Functions................................................ 7-3
AESS Architecture ............................................................................. 7-4
Groups of Functions............................................................................. 7-5
AESS Operating Modes......................................................................... 7-5
AESS Reconfiguration Principles ............................................................ 7-6
TAWS Function .................................................................................. 7-7
TAWS RNP.......................................................................................... 7-7
Selection of Lateral Position Source........................................................ 7-8
Terrain Display in Polar Areas................................................................ 7-8
Weather Radar Function.................................................................... 7-9
Weather Detection............................................................................... 7-9
Enhanced Turbulence Detection........................................................... 7-15
Predictive Wind Shear (PWS) Detection ................................................ 7-15
Ground Mapping................................................................................ 7-16
TCAS Function ................................................................................. 7-16
Transponder Function ..................................................................... 7-16
Vertical Display ............................................................................... 7-16
Generation of Vertical Terrain View ...................................................... 7-18
Generation of Vertical Weather View .................................................... 7-19
Interpretation of Weather and Terrain Elevation on VD ........................... 7-20
AESS Indications ............................................................................. 7-21
Navigation Display (ND) ..................................................................... 7-21
Vertical Display (VD).......................................................................... 7-22
Primary Flight Display (PFD) ............................................................... 7-24
Aural Alerts ...................................................................................... 7-24
AESS Controls.................................................................................. 7-24
KCCU SURV Key................................................................................ 7-25
EFIS Control Panel (EFIS CP) .............................................................. 7-25
SURV Panel ...................................................................................... 7-25
SURV Pages on MFD .......................................................................... 7-25
SQWK Page on RMP ........................................................................... 7-27
7.2.
7.2.1.
Operational Recommendations for AESS ......................................... 7-27
For the Airline ................................................................................. 7-27
-8-
Getting to grips with Surveillance
Table of contents
7.2.1.1.
7.2.1.2.
7.2.1.3.
7.2.1.4.
7.2.2.
7.2.2.1.
7.2.2.2.
7.2.2.3.
7.2.2.4.
Transponder Function ........................................................................ 7-27
TCAS Function .................................................................................. 7-27
TAWS Function ................................................................................. 7-27
Weather Radar Function ..................................................................... 7-28
For the Flight Crew .......................................................................... 7-28
Transponder Function ........................................................................ 7-28
TCAS Function .................................................................................. 7-28
TAWS Function ................................................................................. 7-28
Weather Radar Function ..................................................................... 7-28
7.3.
7.3.1.
7.3.2.
7.3.3.
7.3.4.
Regulations for AESS ....................................................................... 7-28
Transponder Function ..................................................................... 7-29
TCAS Function ................................................................................. 7-29
TAWS Function ................................................................................ 7-29
Weather Radar Function.................................................................. 7-29
7.4.
Manufacturers for AESS................................................................... 7-29
7.5.
7.5.1.
Future Systems ............................................................................... 7-29
Airborne Traffic Situational Awareness (ATSAW) ............................ 7-29
APPENDIX A – WORLDWIDE ADS-B IMPLEMENTATION ..................................A-2
A.1. The European CASCADE program ............................................................... A-2
A.1.1. Description.............................................................................................. A-2
A.1.2. Website................................................................................................... A-2
A.2. The FAA Surveillance and Broadcast Services Program.............................. A-2
A.2.1. Description.............................................................................................. A-2
A.2.2. Website................................................................................................... A-3
A.3. The Australian ADS-B Upper Airspace Program (UAP) ............................... A-3
A.3.1. Description.............................................................................................. A-3
A.3.2. Website................................................................................................... A-4
A.4. Deployment of ADS-B in Asia ..................................................................... A-4
A.4.1. Description.............................................................................................. A-4
A.4.2. Website................................................................................................... A-4
A.5. ADS-B NRA in the Hudson Bay (Canada) .................................................... A-5
A.5.1. Description.............................................................................................. A-5
A.5.2. Website................................................................................................... A-5
APPENDIX B – ADS-B PHRASEOLOGY .....................................................................B-1
APPENDIX C – ATSAW IN TRAIL PROCEDURE (ITP) .........................................C-1
C.1. Definitions.................................................................................................. C-1
C.2. Procedure................................................................................................... C-1
C.2.1. ITP Sequence .......................................................................................... C-1
C.2.2. Aircraft on the Same Direction ................................................................ C-2
-9-
Table of contents
C.2.3.
C.2.4.
C.2.5.
C.2.6.
ITP
ITP
ITP
ITP
Getting to grips with Surveillance
Volume ............................................................................................. C-2
Geometries ....................................................................................... C-4
Distance............................................................................................ C-4
Criteria.............................................................................................. C-6
C.3. Example ..................................................................................................... C-7
C.3.1. PF: Check the Aircraft Performances ....................................................... C-7
C.3.2. PF: Initiate the ITP.................................................................................. C-7
C.3.3. PF: Check the ITP Opportunity and Identify Reference Aircraft............... C-8
C.3.4. PNF: Request the ATC Clearance ............................................................. C-8
C.3.5. PF: Perform the ITP................................................................................. C-9
C.3.6. Specific Cases ....................................................................................... C-10
C.4. Operational environment ......................................................................... C-11
C.5. CRISTAL ITP............................................................................................. C-11
APPENDIX D - ATSAW VISUAL SEPARATION ON APPROACH (VSA) ...........D-1
D.1. Procedure .................................................................................................. D-1
D.1.1. Visual Acquisition of the Preceding Aircraft ............................................ D-2
D.1.2. Clearance for the Maintenance of the Visual Separation with the Preceding
Aircraft .............................................................................................. D-4
D.1.3. Maintenance of Visual Separation on Approach ...................................... D-5
D.2. Operational Environment ........................................................................... D-5
APPENDIX E – NUC, NAC, NIC, SIL...........................................................................E-1
APPENDIX F – IDENTIFICATION OF AN AIRCRAFT ........................................... F-1
APPENDIX G – AVIATION METEOROLOGY REMINDERS.................................. G-1
G.1. Standard Atmosphere ................................................................................ G-1
G.2. Thunderstorms .......................................................................................... G-2
G.2.1. Formation ............................................................................................... G-2
G.2.2. Single Cell ............................................................................................... G-3
G.2.3. Multi-Cell Thunderstorms........................................................................ G-3
G.2.4. Super Cell ............................................................................................... G-3
G.2.5. Oceanic Cell ............................................................................................ G-3
G.2.6. Squall Line .............................................................................................. G-3
G.3. Hail Encounter ........................................................................................... G-4
G.4. Turbulence ................................................................................................. G-4
G.4.1. Clear Air Turbulence (CAT) ..................................................................... G-4
G.4.2. Turbulence Dome .................................................................................... G-4
G.4.3. Thunderstorm Vault ................................................................................ G-4
G.4.4. Downdraft............................................................................................... G-4
G.4.5. Downburst .............................................................................................. G-5
G.4.6. Gust Front ............................................................................................... G-5
- 10 -
Getting to grips with Surveillance
Table of contents
G.4.7. Wind Shear ............................................................................................. G-6
G.4.8. Non-Reflective Weather .......................................................................... G-6
APPENDIX H – LOW LEVEL WIND SHEAR EFFECTS ON AIRCRAFT
PERFORMANCES...............................................................................................................H-1
H.1. Horizontal Wind Shears ............................................................................. H-1
H.1.1. Longitudinal Wind Shears ....................................................................... H-1
H.1.2. Crosswind Shears ................................................................................... H-2
H.2. Vertical Wind Shears.................................................................................. H-3
H.2.1. Effect on Angle of Attack......................................................................... H-3
H.2.2. Downburst Effects................................................................................... H-4
- 11 -
Executive Summary
Getting to grips with Surveillance
EXECUTIVE SUMMARY
1. INTRODUCTION
Safety of air transportation relies on three pillars: Communication, Navigation and
Surveillance. Surveillance provides the flight crew with awareness and alerts
regarding external hazards (traffic, terrain, weather). With the air transportation
increase, Surveillance became of prime importance. The definition of Surveillance
is a question of perspective: flight crew’s perspective or air traffic controller’s
perspective. From the flight crew’s perspective, Surveillance has been distributed
among several systems (transponder, TCAS, TAWS, etc). From the air traffic
controller’s perspective, Surveillance mainly relies on ground receivers (e.g.
radar) and on aircraft transponders.
The goals of this brochure are to:
- Better understand how surveillance systems work
- Compare different surveillance systems that fulfill the same function
- Describe new surveillance systems expected in the near future.
To these ends, the brochure is split into 5 main chapters that describe the main
surveillance functions:
1. The Aircraft Identification and Position Reporting
2. The Traffic Surveillance
3. The Terrain Surveillance
4. The Weather Surveillance
5. The Runway Surveillance
Tha chapter “Aircraft Identification and Position Reporting” focuses on Surveillance
from an air traffic controller’s perspective. Other chapters focus on Surveillance
from the flight crew’s perspective.
These surveillance function can be combined in one single system. For instances:
- T2CAS combines Traffic Surveillance and Terrain Surveillance.
- AESS combines all the function above except the Runway Surveillance.
In each chapter, the reader will find:
- A description of the system that fulfills the function described in the
chapter.
- Operational recommendations for safe and efficient operations.
- Regulations in terms of carriage requirements at ICAO, EASA and FAA levels
(for other areas, refer to local regulations).
- Manufacturers of systems that fulfill the function to identify the different
available solutions.
- Future systems expected in the near future to improve the fulfillment of the
function.
- 12 -
Getting to grips with Surveillance
Executive Summary
2. AIRCRAFT IDENTIFICATION AND POSITION REPORTING
Transponder
Description
To reply to SSR interrogations, the transponder operates in three modes:
- Mode A: transmission of SQUAWK code,
- Mode C: transmission of barometric altitude,
- Mode S: Selective interrogations replied with enriched transmissions.
Transponders are also capable of operating in a broadcasting mode: the ADS-B.
The introduction of ADS-B aims at providing a safer and more cost-effective
surveillance service in regard to the traffic growth. The ADS-B technology enables
three surveillance services (based on the ADS-B OUT data flow):
- ADS-B NRA: ADS-B surveillance in Non-Radar Areas with low traffic density
- ADS-B RAD: ADS-B surveillance backed up by SSR with high traffic density
- ADS-B APT: ADS-B surveillance on airport surfaces.
Transponders proposed on AIRBUS aircraft are all capable of Mode A/C/S,
ELS/EHS, and ADS-B NRA. At the time fo writing the brochure, definitions of
standards for ADS-B RAD and ADS-B APT are in progress.
Operational Recommendations
The main recommendations (but non exhaustive) are:
• The use of the ICAO format (three-letter code) for the flight number
• The use of identical flight numbers in the ICAO flight plan and in the
FMS INIT A page
• An appropriate training regarding ADS-B OUT operations, even there
are no impacts in the cockpit for the flight crew
• A special attention to local implementations of ADS-B
• A correct avionics settings (i.e. 24-bit address)
• A careful flight planning (i.e. flight number, surveillance capability, 24bit address).
Refer to 2.5 – Operational Recommendations for Transponder.
Regulations
The carriage of transponder capable of Mode C is mandatory and the
carriage of transponder capable of Mode S is recommended as per ICAO Annex 6
– Operation of Aircraft – Part I. TCAS compliant with TCAS II Change 7 requires a
Mode S transponder for its functioning. Therefore, the mandatory carriage of
TCAS implies a mandatory carriage of a Mode S transponder.
Future Systems
At the time of writing the brochure, no new transponder is expected on a short
term.
- 13 -
Executive Summary
Getting to grips with Surveillance
3. TRAFFIC SURVEILLANCE
Aircraft Collision Avoidance System – ACAS
Description
ACAS (or commonly named Traffic alert and Collision Avoidance System – TCAS)
as per TCAS II Change 7.0 fulfills the Traffic Surveillance function. It provides
Traffic Advisories (TA), Resolution Advisories (RA), even coordinated RA
when own aircraft and intruders are equipped with Mode S transponders.
TCAS II Change 7.1 introduces a new reversal logic and replaces the RA “ADJUST
VERTICAL SPEED, ADJUST” by a new RA “LEVEL OFF”.
Most TCAS available on AIRBUS aircraft comply with TCAS II Change 7.0: ACSS
TCAS 2000 or T2CAS, Rockwell Collins TTR 921, Honeywell TPA 100A. (P/N 9400300-001). ACSS T3CAS and Honeywell TPA 100A (P/N 940-0351-001) complies
with TCAS II Change 7.1.
Operational Recommendations
The main recommendations (but non exhaustive) are:
• The cognizance of Eurocontrol ACAS II bulletins
• An appropriate and recurrent training on TCAS,
• The conformation to RA in any cases without delay,
• The adequate response to TCAS aural alerts (e.g. ADJUST VERTICAL
SPEED, no flight path change based on TA only, no excessive reaction to
RA),
• The unreliability of TCAS for aircraft self-separation
• The immediate report to ATC in case of RA and when clear of conflict
• The conformation to the initial ATC clearance when clear of conflict.
Refer to 3.2 – Operational Recommendations for TCAS.
Regulations
The carriage of TCAS II is mandatory as per ICAO Annex 6 – Operation of
Aircraft – Part I.
Future Systems
At the time of writing the brochure, no new TCAS is expected on a short term.
Airborne Traffic Situational Awareness – ATSAW
Description
The ATSAW function uses ADS-B data to enhance the Traffic Surveillance of
the flight crew. A new generation of TCAS computers hosts the ATSAW
applications. The introduction of the ATSAW function in the TCAS computer does
not change the ACAS logic and the TCAS procedures. The ACAS and ATSAW
softwares are fully segregated inside the TCAS computer.
- 14 -
Getting to grips with Surveillance
Executive Summary
ATSAW applications are: ATSA AIRB, ATSA VSA, ATSA ITP, ATSA SURF (not
yet available).
TCAS computer capable of ATSAW on AIRBUS aircraft are: new version of
Honeywell TPA 100B (early 2010) and ACSS T3CAS (early 2010).
Operational Recommendations
The main recommendations (but non exhaustive) are:
• An appropriate training on ATSAW with different applications (AIRB, ITP,
VSA)
• A particular attention to flight crew training to ATSA ITP
• The correlation of ATSAW information with visual information out of the
window
• The use of the ATSAW function for traffic awareness only.
Refer to 3.7 – Operational Recommendations for ATSAW.
Regulations
At the time of writing the present brochure, no country has required the carriage
of ATSAW.
Future Systems
To improve the Traffic Surveillance during taxi, AIRBUS is currently developing the
integration of the ATSA SURF application in the OANS for all AIRBUS aircraft.
4. TERRAIN SURVEILLANCE
Enhanced Ground Proximity Warning System (EGPWS) or Terrain Awareness
and Warning System (TAWS) of T2CAS
Description
The Terrain Surveillance function had been previously fulfilled with Ground
Proximity Warning System (GPWS) that includes the reactive/basic functions
(i.e. Mode 1 to 5).
Today, it is fulfilled by Terrain Awareness System (TAWS) with enhanced
functions also known as predictive functions in addition to basic functions. The
main TAWS products available on AIRBUS aircraft are:
• Honeywell EGPWS with its predictive functions: Terrain Awareness and
Display – TAD and Terrain Clearance Floor – TCF ,and Runway Field
Clearance Floor (RFCF).
• ACSS T2CAS with its predictive functions: Collision Prediction and Alerting
– CPA, and Terrain Hazard Display – THD.
• ACSS T3CAS that includes a transponder, a TCAS, and a TAWS module
with Eleview and an obstacle databse.
Refer to 4.1.3.3 – EGPWS/T2CAS Comparison to compare both products.
- 15 -
Executive Summary
Getting to grips with Surveillance
Operational Recommendations
The main recommendations (but non exhaustive) are:
• A regular update of TAWS terrain database
• The implementation of the GPS position into the TAWS architecture
• The activation of predictive TAWS functions
• An appropriate and recurrent training on TAWS
• Good knowledge of TAWS operations and escape maneuvers.
Refer to 4.2 – Operational Recommendations for TAWS.
Regulations
The carriage of TAWS is mandatory as per ICAO Annex 6 – Operation of
Aircraft – Part I.
Future Systems
At the time of writing the brochure, no new TAWS computer is expected on a
short term.
5. RUNWAY SURVEILLANCE
On-board Airport Navigation System – OANS
Description
The On-board Airport Navigation System (OANS) is a new system introduced
by the A380. It improves the flight crew situational awareness during taxi by
locating the aircraft on an airport map.
OANS is NOT designed for guidance on ground and does not change the
current taxi procedures. The flight crew must correlate the OANS
indications with the outside visual references.
Operational Recommendations
The main recommendations (but non exhaustive) are:
• OANS is not a guidance tool
• A regular update of OANS Airport Data Base (ADB)
• The check of NOTAM before taxiing
• The correlation of OANS indications with outside visual references.
Refer to 5.2 – Operational Recommendations for OANS.
Regulations
At the time of writing the present brochure, no country has required the carriage
of OANS.
- 16 -
Getting to grips with Surveillance
Executive Summary
Future Systems
The future evolutions of OANS are expected to be the integration of:
• The ADS-B data for Traffic Surveillance
• Data link applications to display NOTAM and ATC ground clearances.
Runway end Overrun Warning and Protection (ROW/ROP)
Description
The ROW and ROP functions help the flight crew anticipating an overrun of the
runway end at landing. During the final approach, ROW provides aural and visual
indications that invite the flight crew to consider a go around. On the runway, ROP
provides aural and visual indications for the settings of thrust reversers.
ROW/ROP improves the flight crew awareness regarding risks of runway end
overrun.
ROW and ROP are optional functions and used in conjunction with OANS.
Operational Recommendations
The main recommendations (but non exhaustive) are:
• The correct understanding of ROW and ROP indications
• The proper disconnection of the auto brake.
Refer to 5.7 – Operational recommendations for ROW/ROP.
Regulations
At the time of writing the present brochure, no country has required the carriage
of the ROW/ROP functions.
Future Systems
AIRBUS studies the extension of ROW/ROP to the manual braking mode.
Runway Awareness and Advisory System – RAAS
Description
The Runway Awareness and Advisory System (RAAS) is one system that
fulfills the Runway Surveillance function. It is a module of the Honeywell EGPWS.
The RAAS provides advisories about the aircraft position on or out the runway
thanks to the EGPWS runway database. Therefore, the RAAS is unable to locate
taxiways. Anyway, it is able to identify when the aircraft is rolling on a pavement
that is not a runway at high speed.
AIRBUS aircraft had been certified with three call-outs out of ten: Approaching
Runway, On Runway and Take-Off On Taxiway.
The RAAS requires recent EGPWS software version and terrain database.
Operational Recommendations
AIRBUS has no recommendations on RAAS operations.
- 17 -
Executive Summary
Getting to grips with Surveillance
Regulations
At the time of writing the present brochure, no country has required the carriage
of RAAS.
Future Systems
At the time of writing the present brochure, no evolutions are expected, from an
AIRBUS perspective, for RAAS in terms on new functions.
6. WEATHER SURVEILLANCE
Weather Radar
Description
Operating in the X-band frequency (9.3 GHz), the weather radar detects any wet
meteorological phenomena (clouds, precipitations, turbulence). Hence, Clear Air
Turbulence is not detected and a weak reflectivity does not necessarily mean
that the area is safe (e.g. dry hail).
For A300/A310/A320/A330/A340 aircraft, two manufacturers are proposed:
Honeywell (RDR-4B) and Rockwell Collins (WXR701X/2100). The
automatic function (Autotilt for RDR-4B or Multiscan for WXR 2100) is optional.
Operational Recommendations
The main recommendations (but non exhaustive) are:
• An appropriate maintenance of all weather radar components including the
radome
• An appropriate and recurrent training on weather radar
• A sharp knowledge on how to interpret weather radar indications
• An anticipation of the weather ahead the aircraft (take-off, cruise,
approach)
• Regular manual scans
• Use of automatic mode (Autotilt or Multiscan) when manual control is not
necessary
• A good preparation to abort a procedure (take-off or approach) in
case of wind shear
• Do not fly into a thunderstorm. Avoid flying above or below a
thunderstorm.
Refer to 6.2 – Operational Recommendations for Weather Radar.
Regulations
The carriage of a weather radar is recommended as per ICAO Annex 6 –
Operation of Aircraft – Part I. In most countries, the weather radar is required
considering that significant weather may be experienced in most flights. Refer to
local regulations.
- 18 -
Getting to grips with Surveillance
Executive Summary
Future Systems
The Honeywell RDR 4000, already available on A380 aircraft, will introduce the
benefits of the 3D weather scanning on A320/A330/A340 aircraft in 2010 such as:
• The automatic correction of the Earth curvature
• Automatic modes to display on-path and off-path weather
• The elevation mode.
7. AIRCRAFT ENVIRONMENT SURVEILLANCE
Aircraft Environment Surveillance System – AESS
Description
The AESS is an integrated surveillance system on A380 aircraft that includes
the following: transponder, TCAS, TAWS and weather radar with PWS. The TAWS
and the weather radar use the Vertical Display (VD) at best to enhance the
flight crew awareness on terrain and weather.
Thus, the AESS is also able to display on VD the terrain and weather along the
path followed by the aircraft (flight plan, track) or the azimuth selected by the
flight crew. The weather radar also introduces, thanks to the 3D buffer, the onpath and off-path weather concept, the weather view at a selected altitude
(elevation mode).
The AESS controls are distributed on the AESS Control Panel, the EFIS CP, the
MFD SURV page and the RMP SQWK page.
Operational Recommendations
Operational recommendations regarding the AESS functions are the same as the
ones provided for the elementary systems (i.e. XPDR, TCAS, TAWS, WXR). The
VD introduces new logics and features. Therefore, a special attention should
be paid to mechanisms introduced by the VD.
Refer to 7.2 – Operational Recommendations for AESS.
Regulations
Regulations for the integrated AESS are the same as for elementary systems (i.e.
XPDR, TCAS, TAWS, WXR).
Future Systems
To keep pace with the deployment of the ADS-B technology, the AESS is expected
to implement the ATSAW application for an enhanced traffic awareness.
- 19 -
Abbreviations
Getting to grips with Surveillance
ABBREVIATIONS
A/C Aircraft
AMI Airline
Modifiable
Information
Maintenance
AMM Aircraft
Manual
Navigation
Service
ANSP Air
Provider
AOA Angle Of Attack
A/THR Auto Thrust
ABV Above
AC Advisory Circular
ACAS Aircraft
Collision
Avoidance System
ACSS Aviation Communication &
Surveillance Systems
ADB Airport Data Base
AOC Airline Operations Control
AP Auto Pilot
Registration
ARN Aircraft
Number
ASAS Airborne
Separation
Assistance System
A-SMGCS Advanced
–
Surface
Movement Guidance and
Control Systems
ATC Air Traffic Control
ADIRU Air Data and Inertial
Reference Unit
ADR Air Data Reference
ADS Automatic
Dependent
Surveillance
ADS-B Automatic
Dependent
Surveillance – Broadcast
ADS-C Automatic
Dependent
Surveillance – Contract
AESS Aircraft
Environment
Surveillance System
AESU Aircraft
Environment
Surveillance Unit
AFM Aircraft Flight Manual
ATCRBS Air Traffic Control Radar
Beacon System
ATS Air Traffic Service
ATSA or Airborne Traffic Situational
ATSAW Awareness
ATSU Air Traffic Service Unit
BCS Braking Control System
AFS Automatic Flight System
BLW Below
AGL Above Ground Level
AIC Aeronautical
Circular
AIP Aeronautical
Publication
AIRB Airborne
BTV Brake To Vacate
Information
CAA Civil Aviation Authority
Information
CASA Australian Civil Aviation
Safety Authority
CASCADE Co-operative ATS through
Surveillance
and
Communication
Applications Deployed in
ECAC
CAT Clear Air Turbulence
ALA Approach
and
Landing
Accident
ALAR Approach
and
Landing
Accident Reduction
ALT RPTG Altitude Reporting
CDTI Cockpit Display of Traffic
Information
CFIT Controlled
Flight
Into
AMC Acceptable
Means
of
Compliance
AMDB Airport Mapping Data Base
- 20 -
Getting to grips with Surveillance
Abbreviations
Terrain
S
Elementary
ELS Mode
Surveillance
EMMA2 European
airport
Movement
and
Management by A-SMGCS
EPE Estimated Position Error
CMV Concentrator
and
Multiplexer for Video
CNS/ATM Communication Navigation
Surveillance / Air Traffic
Management
CPA Closest Point of Approach
(ACAS)
CPA Collision Prediction and
Alerting (TAWS)
CPDLC Controller Pilot Data Link
Communication
CRISTAL Co-operative Validation of
Surveillance
Techniques
and Applications
CSD Customer Service Director
Position
EPU Estimated
Uncertainty
EWD Engine
and
Warning
Display
FAA Federal
Aviation
Administration
Augmentation
FAC Flight
Computer
Air
Navigation
FANS Future
Systems
FC Flight Crew
DCDU Datalink
Control
and
Display Unit
DCPC Direct
Controller-Pilot
Communication
DMC Display
Management
Computer
DME Distance
Measuring
Equipment
DSNA Direction des Services de
la Navigation Aérienne
DU Display Unit
Crew
Operating
FCOM Flight
Manual
FCU Flight Control Unit
FD Flight Director
Detection
FDE Fault
Exclusion
FE Flight Envelope
and
FLS FMS Landing System
FM Flight Management
EASA European Aviation Safety
Agency
ECAC European Civil Aviation
Conference
ECAM Electronic
Centralized
Aircraft Monitoring
EFIS Electronic
Flight
Instrument System
EFIS CP EFIS Control Panel
FMA Flight Mode Annunciator
Management
FMGEC Flight
Guidance and Envelope
Computer
FMS Flight
Management
System
FOBN Flight Operations Briefing
Note
FPA Flight Path Angle
EGPWM Enhanced
Ground
Proximity Warning Module
EGPWS Enhanced
Ground
Proximity Warning System
EHS Mode
S
Enhanced
Surveillance
EIS Electronic
Instrument
System
FSF Flight Safety Foundation
FWS Flight Warning System
G/S Glide Slope
Collision
GCAS Ground
Avoidance System
GCS Ground
Clutter
- 21 -
Abbreviations
Getting to grips with Surveillance
Suppression
Terrain
MTCD Minimum
Clearance Distance
MTOW Maximum Take Off Weight
GPIRS Global
Positioning
and
Inertial Reference System
GPS Global Positioning System
NAC Navigational
Accuracy
Category
NAS National Airspace System
GPS-SU GPS Single Unit
GPWC Ground Proximity Warning
Computer
GPWS Ground Proximity Warning
System
GS Ground Speed
NASA USA National Aeronautics
and Space Administration
NATOTS North Atlantic Organized
Track System
Air
Traffic
NATS National
Services (UK)
ND Navigation Display
HFOM Horizontal Figure Of Merit
HIL Horizontal Integrity Limit
HPL Horizontal Protection Limit
Generation
Air
NGATS or Next
System
NextGen Transportation
(USA)
Integrity
NIC Navigational
Category
NLC Noctilucent Cloud
IAS Indicated Air Speed
ICAO International Civil Aviation
Organization
ID Identification
IMC Instrument Meteorological
Conditions
IR Inertial Reference
NOTAM Notice To Air Men
NPRM Notice of Proposed Rule
Making
NUC Navigational
Uncertainty
Category
OANS On-board
Airport
Navigation System
OIT Operator
Information
Telex
OTS Organized Track System
ITP In Trail Procedure
KCCU Keyboard
and
Cursor
Control Unit
LAHSO Land And Hold Short
Operations
LDA Landing Distance Available
LDG Landing
LGERS Landing Gear Extension
and Retraction System
LSK Line Select Key
MAC Mean Aerodynamic Chord
MCDU Multipurpose Control
Display Unit
MFD Multi Function Display
&
MMO Maximum Operating Mach
MMR Multi-Mode Receiver
MNPS Minimum
Navigation
Performance Specification
MSL Mean Sea Level
P/N Part Number
Attenuation
PAC Path
Compensation
PANS-ATM Procedures
for
Air
Navigation Services – Air
Traffic Management
PANS-OPS Procedures
for
Air
Navigation
Services
–
Operations
for
Air
PANS-RAC Procedures
Navigation
Services
–
Rules of the Air and Air
Traffic Services
PDA Premature Descent Alert
- 22 -
Getting to grips with Surveillance
Abbreviations
PF Pilot Flying
SCP Soft Control Panel
SF Severity Factor
PFD Primary Flight Display
PNF Pilot Non Flying
SIL Service Information Letter
PPOS Present Position
SIL Surveillance
Integrity
Level
SMR Surface Movement Radar
PRIM Primary Flight Control and
Guidance Computer
PSR Primary
Surveillance
Radar
PWS Predictive Wind Shear
Operating
SOP Standard
Procedure
SPI Special
Position
Identification
SPP Soft Pin Programming
R/T Receiver / Transmitter
RA Radio Altitude
SQWK Squawk
RA Resolution
Advisory
(ACAS)
RAAS Runway Awareness and
Advisory System
RADAR Radio
Detection
And
Ranging
RAIM Receiver
Autonomous
Integrity Monitoring
RCD RAAS
Configuration
Database
RFCF Runway Field Clearance
Floor
RMP Radio Management Panel
SSR Secondary
Radar
STBY Stand-By
Surveillance
STC Sensitivity Time Control
SURF Surface
and
Terrain
T/TISS Traffic
Integrated
Surveillance
System
and
Terrain
T2CAS Traffic
Collision
Avoidance
System
TA Traffic Advisory
RNP AR Required
Navigation
Performance Authorization
Required
ROP Runway
end
Overrun
Protection
ROT Runway Occupancy Time
TAAATS The Australian Advanced
Air Traffic System
TAU It is not an acronym but
the Greek letter τ.
TAWS Terrain Awareness and
Warning System
TCAS Traffic alert and Collision
Avoidance System
TCF Terrain Clearance Floor
ROW Runway
end
Overrun
Warning
RTO Rejected Take Off
RVSM Reduced
Vertical
Separation Minima
RWY Runway
THD Terrain Hazard Display
THRT Threat
Information
TIBA Traffic
Broadcasts by Aircraft
UAP Upper Airspace Program
(Australia)
UAT Universal
Access
Transceiver
S&M Sequencing and Merging
SA Selective Availability
SARPs Standards
And
Recommended Practices
SAT Static Air Temperature
- 23 -
Abbreviations
Getting to grips with Surveillance
V/S Vertical Speed
VD Vertical Display
VDL VHF Data Link
VLS Lowest Selectable Speed
VMC Visual
Meteorological
Conditions
VMO Maximum
Operating
Speed
VSA Visual
Separation
on
Approach
VSI Vertical Speed Indicator
WAM Wide Area Multi-lateration
WGS84 World Geodetic
revised in 1984
WX Weather
System
WXR Weather Radar
XLS Landing System (ILS, FLS,
GLS)
XPDR Transponder
- 24 -
Getting to grips with Surveillance
References
REFERENCES
REF 1
ICAO documents available at http://www.icao.int/icao/en/sales:
- Procedures for Air Navigation Services – Air Traffic
Management (PANS-ATM), Doc 4444, Fifteenth Edition, 2007.
- Procedures for Air Navigation Services – Aircraft
Operations (PANS-OPS), Doc 8168, Fifth Edition, 2006.
- Regional Supplementary Procedures, Doc 7030, Fourth
Edition, 2006,
- Manual on Low-level Wind Shear and Turbulence, Doc
9817, First Edition, 2005.
- Airborne Collision Avoidance System (ACAS) Manual, Doc
9863, First Edition, 2006.
- Designators for Aircraft Operating Agencies, Aeronautical
Authorities and Services, Doc 8585, Edition 142, October
2007.
- Operation of Aircraft – International Commercial Air
Transport – Aeroplanes, Annex 6, Part I, Eighth Edition, July
2001.
- Aeronautical
Telecommunications
–
Communication
Procedures including those with PANS status, Annex 10,
Volume II, Sixth Edition, October 2001.
- Aeronautical Telecommunications – Surveillance and
Collision Avoidance Systems, Annex 10, Volume IV, Fourth
Edition, July 2007.
- Air Traffic Services, Annex 11, Thirteenth Edition, July 2001.
REF 2
Eurocontrol documents:
- ACAS II Bulletins available at
http://www.eurocontrol.int/msa/public/standard_page/ACAS_Bull
etins_Safety_Messages.html.
- Specimen AIC – Carriage and Operation of SSR Mode S
Airborne Equipment in European Airspace, version 2, March
2005 available at
http://www.eurocontrol.int/msa/public/standard_page/modes_do
cs_aics_aics.html,
- Flight Crew Guidance for Flight Operations in ADS-B only
Surveillance Airspaces, version 1, February 2008, available at
http://www.eurocontrol.int/cascade/public/subsite_homepage/ho
mepage.html.
- Wide Area Multi-lateration Report, NLR-CR-2004-472,
National Aerospace Laboratory (NLR), August 2005 available at:
http://www.eurocontrol.int/surveillance/public/standard_page/lib
rary.html.
REF 3
European Aviation Safety Agency (EASA) documents:
- Commercial air transportation (aeroplanes), EU-OPS 1, July
2008.
- 25 -
References
Getting to grips with Surveillance
-
Certification Considerations for the Enhanced ATS in NonRadar Areas using ADS-B Surveillance (ADS-B-NRA)
Application, AMC 20-24, May 2008, available at
http://www.easa.europa.eu/ws_prod/g/rg_certspecs.php.
REF 4
Federal
Aviation
Administration
(FAA)
documents
at
http://www.faa.gov/regulations_policies/:
- Aviation Weather for Pilots and Flight Operations
Personnel, AC 00-6A, January 1975.
- Thunderstorms, AC 00-24B, January 1983.
- Atmospheric Turbulence Avoidance, AC 00-30B, September
1997.
- Pilot Wind Shear Guide, AC 00-54, November 1988.
- Recommended Radiation Safety Precautions for Ground
Operation of Airborne Weather Radar, AC 20-68B, August
1980.
- Airworthiness Criteria for the Approval of Airborne Wind
Shear Warning Systems in Transport Category, AC 25-12,
November 1987.
- Aircraft Wake Turbulence 1, AC 90-23F, February 2002.
- Guidelines for Operational Approval of Wind Shear Training
Programs, AC 120-50A, September 1996.
- Aircraft Surveillance Systems and Applications, AC 120-86,
September 2005.
- NPRM
Automatic
Dependent
Surveillance—Broadcast
(ADS–B) Out Performance Requirements to Support Air
Traffic Control (ATC) Service, October 2007, available at
http://www.faa.gov/regulations_policies/rulemaking/recently_pu
blished/.
REF 5
Civil Aviation Safety Authority (CASA) Australia documents:
- Airworthiness Approval of Airborne Automatic Dependent
Surveillance Broadcast Equipment, AC 21-45, April 2007,
available at http://www.casa.gov.au/rules/1998casr/021/.
- Civil Aviation Order 20.18 Amendment Order (No. 1) 2009,
February 2009, available at http://casa.gov.au/index.htm.
REF 6
Airservives Australia documents about ADS-B operations available at
https://www.airservicesaustralia.com/projectsservices/projects/adsb/defa
ult.asp:
- Flight Operations Information Package,
- CASA Pilot Information Booklet.
REF 7
Transport Canada documents:
- Automatic Dependent Surveillance – Broadcast, AC 700-009,
July 2008, available at
http://www.tc.gc.ca/CivilAviation/IMSdoc/ACs/menu.htm.
1
Thanks to AIRBUS flight test campaign about wake vortices with modern measuring instruments,
international standards about wake vortices are being reviewed.
- 26 -
Getting to grips with Surveillance
References
REF 8
NAV Canada documents:
- Introduction
of
Automatic
Dependent
Surveillance
Broadcast (ADS-B) Airspace in the Vicinity of Hudson Bay,
AIC
34/08,
August
2008,
available
at
http://www.navcanada.ca/NavCanada.asp?Language=EN&Conten
t=ContentDefinitionFiles/Publications/AeronauticalInfoProducts/AI
P/Current/default.xml.
- NAV CANADA ADS-B Information Brochure available at
http://www.navcanada.ca/NavCanada.asp?Content=ContentDefin
itionFiles\Services\ANSPrograms\ADS-B\default.xml
REF 9
Introduction to TCAS II Version 7, FAA, November 2000 at
http://www.arinc.com/tcas/.
REF 10 Enhanced Ground Proximity Warning System (EGPWS)
http://www51.honeywell.com/aero/Products-Services/AvionicsElectronics/EGPWS-Home.html?c=21.
at
REF 11 Terrain and Traffic Collision Avoidance System (T2CAS)
http://www.acssonboard.com/products/Pages/Welcome.aspx.
at
REF 12 Product Description Honeywell International Inc. Runway
Awareness and Advisory System (RAAS), Revision D, April 2003 at
http://www51.honeywell.com/aero/Products-Services/AvionicsElectronics/Egpws-Home3/raas4/raas_certifications.html?c=21.
REF 13 Collins WXR-2100 MultiScan™ Radar Fully Automatic Weather
Radar – Operator’s Guide, 1st revision, 1st edition, September 2003 at
https://www.shopcollins.com/portal/server.pt?open=512&objID=239&mo
de=2&in_hi_userid=200&cached=true.
REF 14 Honeywell
RDR-4B
–
Forward
Looking
Windshear
Detection/Weather Radar System – User’ Manual with Radar
Operating
Guidelines,
Rev
6,
February
2004
at
https://pubs.cas.honeywell.com/.
REF 15 Flight Safety Foundation publications on Approach-and-Landing
Accidents (ALA) and Controlled Flight Into Terrain (CFIT) at
http://www.flightsafety.org (“Technical Initiatives” section: ALAR and
CFIT).
REF 16 Wind Shear Training Aid, ref PB88127196, US National Technical
Information Service at www.ntis.gov.
REF 17 Air Transport World webcast “Not Your Father's Radar – How
current
technology
is
reducing
training
costs”
at
http://www.atwonline.com/webcasts/archive.html.
REF 18 Thales On-board Airport Navigation System (OANS) leaflet at
http://www.thalesonline.com/markets/Activities/Aircraftmanufacturers/Navigation.html.
- 27 -
References
Getting to grips with Surveillance
AIRBUS REFERENCES
REF 19 Flight Crew Operating Manual (FCOM) as available in your company.
REF 20 Flight Crew Training Manual (FCTM) as available in your company.
REF 21 Computer Based Training (CBT), Full Flight Crew Courses, as per
your aircraft model.
REF 22 Safety
First
Magazine
on
Airbus
World
at
https://w3.airbus.com/crs/A233_Flight_Ops_GN60_Inst_Supp/Portlet/saf
ety_mag.htm via Flight Operations Community:
- Edition #1, January 2005: Go-around at Addis Ababa due to
VOR reception problems.
- Edition #2, September 2005: Managing Severe Turbulence.
- Edition #4, June 2007:
o Do you know your ATC/TCAS panel?
o Managing hailstorms,
o Terrain
Awareness
and
Warning
Systems
operations based on GPS data.
- Edition #7, February 2009: Airbus AP/FD TCAS mode: a new
step towards safety improvement.
REF 23 AIRBUS Flight Operations Briefing Notes (FOBN) on Airbus World at
https://w3.airbus.com/crs/A233_Flight_Ops_GN60_Inst_Supp/FOBN/inde
x01.htm via Flight Operations Community:
- Human Performance:
o Effective Pilot/Controller Communications, Rev 3,
September 2004,
o Enhancing Situational Awareness, Rev 1, July 2007,
o Visual Illusion Awareness, Rev 2, September 2005.
- Operating Environment – Enhancing Terrain Awareness,
Rev 3, June 2007.
- Runway & Surface Operations – Preventing Runway
Incursions, Rev 1, May 2004.
- Adverse Weather Operations:
o Optimum Use of the Weather Radar, Rev 2,
February 2007,
o Wind Shear Awareness, Rev 2, November 2005.
- Supplementary Techniques:
o Use of Radio Altimeter, Rev 3, December 2005,
o Preventing Altitude Deviations/Level Busts, Rev 2,
May 2005.
- Take-off and Departure Operations – Revisiting the STOP
OR GO Decision, Rev 1, December 2005.
- Approach Techniques:
o Flying Stabilized Approaches, Rev 2, October 2006,
o Aircraft Energy Management during Approach, Rev
2, October 2005.
- 28 -
Getting to grips with Surveillance
References
REF 24 Service
Information
Letter
(SIL)
on
Airbus
World
at
https://services.airbus.com/ym01/SIL/firstscreenlayout.htm:
- Map Shift Events and EGPWS False Warning Associated, 22043, Rev 0, January 2005.
- "Terrain Awareness and Warning System" (TAWS) on
AIRBUS Aircraft, 34-080, Rev 8, December 2008.
REF 25 Operators
Information
Telex
(OIT)
on
Airbus
World
at
https://w3.airbus.com via Flight Operations community and Operational
Standards/FOT channel:
- AIRBUS Policy Concerning The Use Of GPS Position For
Terrain
Awareness
And
Warning
System
(TAWS)
Operations, OIT 999.0015/04/VHR, February 2004.
- AIRBUS Offer For Standard Service Bulletins Installing
EGPWS PN965-1676-002 Enabling Direct Use Of GPS Data
And Additional New functions, OIT 999.0050/06/VHR, April
2006.
- AIRBUS Offer For Standard Service Bulletins Awaiting
Alternate Vertical Position And Alternate Lateral Position
Based On GPS (MMR) For T2CAS, OIT 999.0034/07/VHR,
March 2007.
- Automatic Dependent Surveillance - Broadcast OUT (ADS-B
OUT) via ATC Transponders on AIRBUS Aircraft, OIT
999.0057/08/BB, June 2008.
REF 26 ADS-B OUT Capability Declaration as referenced in your AFM. Contact
your Customer Service Director (CSD) to get a copy.
REF 27 Getting to grips with FANS, Issue III – April 2007 on Airbus World at
https://w3.airbus.com/crs/A233_Flight_Ops_GN60_Inst_Supp/Portlet/saf
ety_OED.htm via Flight Operations Community.
- 29 -
References
Getting to grips with Surveillance
AIRBUS CATALOGUES
AIRBUS Standard Offer documentation on Airbus World at
https://w3.airbus.com/CDIS/DOC/GEN/initedocgen.do?DA=N&serviceId=1142.
AIRBUS Upgrade Services e-Catalogue on Airbus World at
https://w3.airbus.com/upgrade-ecatalogue/index.jsp.
Contact your Customer Service Director (CSD) for any questions related to these
catalogues.
AIRBUSWORLD SUPPORT 24/7
To get the initial access to Airbus World for your company, please contact your
Customer Service Director (CSD).
To get a login and password, please contact the Airbus World administrator inside
your company.
For any problems related to your access to Airbus World, please contact the
Airbus World Support:
Tel: +33 5 67 19 11 00
E-mail: [email protected]
Airbus World homepage: http://www.airbusworld.com
- 30 -
Getting to grips with Surveillance
1 – Introduction
1. INTRODUCTION
1.1
1.1.1
1.1.2
1.2
1.2.1
1.2.2
1.2.3
1.3
What is Surveillance?
Surveillance from the Flight Crew’s Perspective
Surveillance from the Air Traffic Controller’s
Perspective
How to Read the Brochure?
Surveillance Systems and Functions
Chapter Structure
Captions
System Summary
- 1-1 -
1-2
1-2
1-3
1-3
1-3
1-4
1-4
1-5
1 – Introduction
Getting to grips with Surveillance
Since the advent of the air transportation, safety has been the keystone of this
business. Safety rests on three pillars, which are Communication, Navigation
and Surveillance. Communication and Navigation had been developed before the
air transportation became massive. The traffic getting denser and denser,
Surveillance became more and more necessary.
The very first surveillance tool appeared in the 1930’s: the radar. Widely used
during the Second World War, the radar has come into general use for various
purposes (air traffic control, weather monitoring, road speed control, etc). While
the air traffic becomes denser, safety calls for new surveillance tools other than
the radar. Thus, several surveillance systems were developed like:
- The transponder that works with the ground Secondary Surveillance
Radar (SSR)
- The Traffic Collision Avoidance System (TCAS)
- The Terrain Awareness and Warning System (TAWS)
- The Weather Radar (WXR)
All these systems work for a better awareness of the traffic and the environment
around the aircraft for either the flight crew or the air traffic controller.
Today technology allows getting a more accurate awareness of traffic and
environment. This is the purpose of Automatic Dependent Surveillance –
Broadcast (ADS-B), Airborne Traffic Situational Awareness (ATSAW)
applications, Runway Awareness and Advisory System (RAAS) and Onboard Airport Navigation System (OANS). And the constant traffic growth will
call for other new systems to meet the safety requirements.
In three paragraphs, the reader may have noticed the endless list of surveillance
systems available in the cockpit. Therefore, the aim of this brochure is for our
customers:
• Already equipped with one of these systems:
- To decode all these acronyms
- To understand how these systems work
- To efficiently use these systems.
• Not equipped with some of these systems: to select the right systems
according to their needs.
1.1.
WHAT IS SURVEILLANCE?
The definition of surveillance is a question of perspective: either flight crew’s
perspective or air traffic controller’s one.
1.1.1.
SURVEILLANCE FROM THE FLIGHT CREW’S PERSPECTIVE
At the flight crew level, there are two kinds of surveillance: the air-to-ground
surveillance and the air-to-air one.
Flight crews and air traffic controllers commonly share the air-to-ground
surveillance. The air-to-ground surveillance enables the air traffic controller to
- 1-2 -
Getting to grips with Surveillance
1 – Introduction
manage the traffic in a safe and efficient manner. The air-to-ground surveillance
uses:
- When inside radar coverage, the well-known transponder coupled with SSR
- When outside radar coverage, voice position reports at regular intervals or
ADS-C application
- In specific areas, ADS-B.
The air-to-air surveillance is in the interest of flight crews only. It provides the
flight crew with:
- Assistance to build an aircraft environment awareness regarding external
hazards (traffic, terrain, weather)
- Alerts against these external hazards.
1.1.2.
SURVEILLANCE FROM THE AIR TRAFFIC CONTROLLER’S PERSPECTIVE
At the air traffic controller level, the surveillance may be either cooperative or
non-cooperative, dependent or independent according to the type of the
ground receiver and the aircraft equipment. Refer to 2 – Aircraft identification and
position reporting for more details.
1.2.
HOW TO READ THE BROCHURE?
It is agreed that there is a wealth of literature about aircraft systems available for
pilots (e.g. FCOM, FCTM, CBT). Consequently, the present brochure does not
supersede documents that already exist. The present brochure provides
information to:
• Better understand how surveillance systems work
• Compare different surveillance systems that fulfill the same function
• Describe new surveillance systems expected in the near future.
1.2.1.
SURVEILLANCE SYSTEMS AND FUNCTIONS
The present brochure describes surveillance systems from an operational
perspective. Therefore, each chapter of the present brochure describes a
surveillance function. Each surveillance function refers to one or several systems.
The 5 main surveillance functions are:
1. The Aircraft Identification and Position Reporting: The most
commonly used system is the transponder coupled with a SSR. But other
systems like ADS-C or ADS-B are available to fulfill this function.
2. The Traffic Surveillance: The well-known TCAS provides alerts and
guidance to avoid aircraft that are too close. The ATSAW application
clearly identifies surrounding aircraft and their characteristics (e.g.
heading, speed, wake vortex category, etc).
3. The Terrain Surveillance: Enhanced Ground Proximity Warning System
(EGPWS) and TAWS module of Traffic and Terrain Collision Avoidance
System (T2CAS) are TAWS to prevent Controlled Flight Into Terrain
(CFIT).
4. The Weather Surveillance: The weather radar detects and displays wet
meteorological activities (i.e. clouds, precipitations, turbulence) on
- 1-3 -
1 – Introduction
Getting to grips with Surveillance
Navigation Displays (NDs). The weather detection uses different methods
(Autotilt, Multiscan, or 3D buffer) according to the manufacturer.
5. The Runway Surveillance: OANS displays the aircraft position on an
airport map to improve the flight crew situational awareness. The
ROW/ROP functions in conjunction with OANS provide warnings (visual
and aural) and protection against runway end overruns. RAAS is a module
of EGPWS and provides aural messages regarding the aircraft position on
or out the runway.
These surveillance function can be combined in one single system. For instances:
- T2CAS combines Traffic Surveillance and Terrain Surveillance.
- T3CAS combines Aircraft Identification and Position Reporting, Traffic
Surveillance, and Terrain Surveillance.
- AESS combines all the function above except the Runway Surveillance.
1.2.2.
CHAPTER STRUCTURE
Each of the following chapters describes one of the six functions listed above. For
an easy reading, all of the chapters apply the same structure as follows:
•
•
•
•
•
Description of the system that fulfills the function described in the chapter.
Operational recommendations for safe and efficient operations.
Regulations in terms of carriage requirements at ICAO, EASA and FAA levels
(for other areas, refer to local regulations).
Manufacturers of systems that fulfill the function to identify the different
available solutions.
Future systems expected in the near future to improve the fulfillment of the
function.
Each time several systems of fairly different technologies fulfill a given function,
the description of each system follows the same structure. Therefore, it is easier
to compare the systems.
At the end of each chapter, a summary provides the essential information:
“Please bear in mind…”.
Note: The description of a system focuses on the basic principles. Consequently,
a system is not exhaustively described. For instance, the Electronic Centralized
Aircraft Monitoring (ECAM) alerts when a failure occurs are not described. The
reader should refer to her/his Flight Crew Operating Manual (FCOM) when
necessary.
1.2.3.
CAPTIONS
Grey frames highlight summaries “Please bear in mind…” and important remarks.
Light brown frames highlight very important remarks.
OPS+
An OPS+ flag identifies features that provide significant operational benefits.
- 1-4 -
Getting to grips with Surveillance
1 – Introduction
Tips
Turquoise frames highlight operational tips.
Grey highlights identify interactive cross-references.
1.3.
SYSTEM SUMMARY
The following table gives the functions and the related systems. The reader can
click on the table to directly go to the corresponding page.
Click on a function or system name to jump to the appropriate page.
New
systems
Traffic
Surveillance
Terrain
Surveillance
Weather
Surveillance
Runway
Surveillance
Air-to-Air
A/C
Identification
and Position
Reporting
Existing
systems
Function
Air-toGround
XPDR with
Mode A, C or S
ACAS
TAWS
WX Radar 1
RAAS
WX Radar
with 3D
buffer 2
XPDR with
ADS-B
AP/FD TCAS
OANS
ATSAW 3
ROW/
ROP 4
Note: Some systems (i.e. T2CAS, T3CAS, AESS) combine different functions.
Refer to 1.2.1 – Surveillance Systems and Functions.
1
WX Radar takes into account Rockweel Collins Multiscan and Honeywell Autotilt.
The Rockwell Collins Multiscan weather radar and the AESS use a 3D buffer.
3
ATSAW is a module of some TCAS computer.
4
ROW/ROP is used in conjunction with OANS.
2
- 1-5 -
Getting to grips with Surveillance
2 – Aircraft identification and position reporting
2. AIRCRAFT IDENTIFICATION AND POSITION REPORTING
2.1
2.1.1
2.1.2
2.1.3
2.1.3.1
2.1.3.2
2.1.3.3
2.1.3.7
2.1.3.8
2.1.3.9
2.1.4
2.2
2.2.1
2.2.2
2.2.3
2.2.4
2.2.5
2.2.6
2.2.7
2.2.8
2.2.9
2.2.10
2.2.11
2.2.12
2.2.13
2.2.14
2.2.15
2.2.16
2.2.17
2.3
2.4
Description of Transponder
Mode A
Mode C
Mode S
Mode S Data Link
Elementary Surveillance (ELS)
Enhanced Surveillance (EHS)
Automatic Dependent Surveillance – Broadcast (ADS-B)
Extended Squitter
1090 Extended Squitter
Transponder Controls
Aircraft Identification and Position Reporting with ADS-B
ADS-B Surveillance in Non-Radar Areas (ADS-B NRA)
ADS-B surveillance in Radar Areas (ADS-B RAD)
ADS-B Surveillance on Airport Surfaces (ADS-B APT)
Generic Emergency Indicator
Discrete Emergency Codes
DO-260 and DO-260A
Geographical Filtering of SQWK Code
Version Number
Receiver Autonomous Integrity Monitoring (RAIM) /
Fault Detection and Exclusion (FDE)
GPS Horizontal Figure of Merit (HFOM)
GPS Horizontal Protection Limit (HPL)
Selective Availability (SA)
Navigational Uncertainty Category (NUC)
Navigation Integrity Category (NIC)
Navigational Accuracy Category (NAC)
Surveillance Integrity Level (SIL)
ADS-B Controls and Indications
Aircraft Identification and Position Reporting with Wide
Area Multilateration
Aircraft identification and Position Reporting with FANS
- 2-1 -
2-3
2-4
2-4
2-4
2-5
2-5
2-5
2-6
2-7
2-7
2-8
2-8
2-9
2-10
2-10
2-11
2-11
2-11
2-12
2-12
2-12
2-13
2-13
2-13
2-14
2-14
2-14
2-14
2-15
2-15
2-17
2 – Aircraft identification and position reporting
2.5
2.5.1
2.5.1.1
2.5.1.2
2.5.2
2.5.2.1
2.5.2.2
2.6
2.6.1
2.6.2
2.7
2.7.1
2.7.3
2.7.4
2.8
Getting to grips with Surveillance
Operational Recommendations for Transponder
Conventional Transponder Operations
For the Airline
For the Flight Crew
ADS-B Operations
For the Airline
For the Flight Crew
Regulations for Transponder
Carriage of Transponder
Operational Approval of ADS-B OUT
Manufacturers for Transponder
ACSS XS 950
Rockwell Collins TPR 901
Honeywell TRA 67A
Future Systems
- 2-2 -
2-17
2-17
2-17
2-18
2-18
2-18
2-18
2-19
2-19
2-20
2-21
2-22
2-22
2-22
2-22
Getting to grips with Surveillance
2 – Aircraft identification and position reporting
Since the beginning of the aviation history, air traffic controllers have used the
surveillance radar for years. Today, other surveillance methods are available
with the emergence of new technologies: Automatic Dependent Surveillance
– Contract (ADS-C), Automatic Dependent Surveillance – Broadcast (ADS-B),
and Wide Area Multilateration (WAM). These new surveillance methods aim at the
same goal: the fulfillment of the aircraft identification and position reporting
function in areas where the installation of radar is not cost-effective.
Regardless of the technology, a surveillance method may be either:
- Dependent: The aircraft sends its position to the ground station, or
- Independent: The aircraft does not send any position data to the ground
station. The ground station calculates the aircraft position, or
- Cooperative: The method requires an active system onboard the aircraft, or
- Non-cooperative: The method does not require any system onboard the
aircraft.
Independent
Dependent
Non-cooperative
PSR
SSR – Mode A, C, S
Cooperative
ADS-C, ADS-B
WAM
This chapter reviews all the surveillance methods available for the aircraft
identification and position reporting function.
2.1.
DESCRIPTION OF TRANSPONDER
The aircraft identification and position
reporting
function
requires
a
transponder
onboard
where
a
Interrogation
Secondary
Surveillance
Radar
1030 MHz
(SSR 1) is in operation. The SSR
interrogates the transponder on 1030
Reply
MHz and waits for a reply from the
1090 MHz
transponder on 1090 MHz (refer to
Figure 2-1). Based on this principle, the
SSR operates in three different modes:
Figure 2-1: SSR interrogation and
transponder reply
Mode A, Mode C, and Mode S.
The interrogation mode determines the reply content. For instance, when the
ground station interrogates an aircraft for its altitude, the transponder replies in
Mode C. Other modes exist (Modes 1, 2, 4 and 5) but they are used in military
aviation only.
Surveillance method based on SSR is:
- Cooperative as the SSR interrogates the airborne transponders
to identify the aircraft
1
In some documents, the reader may find the acronym ATCRBS for Air Traffic Control Radar Beacon
System. It designates the SSR.
- 2-3 -
2 – Aircraft identification and position reporting
-
Getting to grips with Surveillance
Independent as the SSR calculates the horizontal 2aircraft
position (i.e. bearing) according to the signal from the
transponder reply.
The Primary Surveillance Radar (PSR) is used for military purposes, as it
detects any vehicles that reflect the radar signal, and for civilian purposes coupled
with an SSR. The surveillance method using a PSR is then non-cooperative and
independent.
Most readers would certainly know what are behind Mode A and Mode C, as they
have operated these modes for years. But, recently the reader may have heard
about the Mode S and various designations (e.g. ELS, EHS, extended squitter,
ADS-B). The following paragraphs provide the reader with a clear view of the
different modes.
2.1.1.
MODE A
When a SSR interrogates a transponder in Mode A, the transponder replies with
the aircraft identification (SQWK code – also called Mode A code – on four octal
digits from 0000 to 7777). The SQWK code format permits 4096 different codes.
The ATC controller may have difficulties to differentiate aircraft:
- When an aircraft enters the ATC sector and transmits the same SQWK code
than another aircraft already present in the ATC sector, or
- When plots of several aircraft on the ATC controller’s screen appear in a small
area.
The IDENT function (also called Special Position Identification, SPI), when
activated by the flight crew, highlights the aircraft plot on the ATC controller’s
screen. This function is available in Mode A, C, or S.
2.1.2.
MODE C
When a SSR interrogates a transponder in Mode C, the transponder replies with
the aircraft barometric altitude.
2.1.3.
MODE S
When a SSR interrogates a transponder in Mode S, the transponder replies with a
large set of surveillance data (e.g. flight number, 24-bit address, speeds, heading,
track, selected altitude, air/ground status, etc).
There are three types of interrogation:
1. All Call interrogation: All Mode A and C transponders reply. Mode S
transponders do not reply to this interrogation.
2. Mode S All Call interrogation: It is a variant of the All Call interrogation
where only Mode S transponders reply. The reply contains the 24-bit
address that enables selective interrogations.
2
The SSR determines the altitude via a Mode C interrogation. The transponder includes the barometric
altitude in its reply.
- 2-4 -
Getting to grips with Surveillance
2 – Aircraft identification and position reporting
3. Selective 3 interrogation: The SSR selectively interrogates a Mode S
transponder.A selective interrogation prevents multiple replies from other
transponders and alleviates the occupancy of the reply frequency. In Mode
S, the SSR uses the 24-bit address to interrogate a selected aircraft.
Refer to 2.1.3.6 – 24-bit Address or Mode S Address.
A Mode S transponder is able to respond to Modes A and C interrogations.
A Mode S SSR is either basic or capable of Elementary Surveillance
(ELS)/Enhanced Surveillance (EHS):
- Basic: The Mode S SSR performs selective interrogations to a given aircraft in
order to get the SQWK code via Mode A, the altitude via Mode C, and other
information (e.g. Airborne/Ground status).
- Capable of ELS/EHS: In addition to the basic capability, ELS and EHS
interrogations enable the collection of several data, on ground requests, such
as the flight number, speeds, heading, track, selected altitude, etc.
The Mode S lexicon
The entry into operation of Mode S introduces new terms. Hereinafter, the Mode S
lexicon describes the main terms.
2.1.3.1.
MODE S DATA LINK
Thanks to the Mode S, the ground can selectively collect a large set of data.
Therefore, the reader may find the designation “Mode S data link” in the literature.
2.1.3.2.
ELEMENTARY SURVEILLANCE (ELS)
The Elementary surveillance refers to a set of Mode S data link messages. These
messages convey parameters such as:
- The aircraft 24-bit address,
- The flight number,
- The aircraft altitude,
- The RA report, etc.
2.1.3.3.
ENHANCED SURVEILLANCE (EHS)
The Enhanced surveillance refers to the data link message set of the Elementary
surveillance plus an additional set of data link messages. These additional
messages convey parameters such as:
- The selected altitude,
- The ground speed,
- The barometric pressure setting, - The true air speed,
- The roll angle,
- The magnetic heading,
- The track angle rate,
- The indicated airspeed,
- The true track angle,
- The Mach number, etc.
3
Mode S stands for Selective.
- 2-5 -
2 – Aircraft identification and position reporting
2.1.3.4.
Getting to grips with Surveillance
GROUND INITIATED COMM B (GCIB)
The Mode S ELS/EHS is sometimes called GCIB. It indicates that data are
transmitted following an interrogation from the ground. GCIB is different from
Extended Squitters (refer to 2.1.3.8 – Extended Squitter) that transmit data
without solicitation.
2.1.3.5.
COMM A AND COMM B
Comm A is communication protocol for an interrogation of 56 or 112 bits on 1030
MHz from the ground to the aircraft.
Comm B is a communication protocol for a reply of 56 or 112 bits on 1090 MHz
(following a Comm A interrogation) from the aircraft to the ground.
2.1.3.6.
24-BIT ADDRESS OR MODE S ADDRESS
The 24-bit address is also called Mode S address of aircraft ICAO code. The 24-bit
address format permits 16 777 216 different addresses. Therefore, each aircraft
has its own 24-bit address, and a selective interrogation is possible.
The State of Registry delivers the 24-bit address with the aircraft registration
documents. The 24-bit address is usually given on 6 digits (hexadecimal format) or
on 8 digits (octal format).
2.1.3.7.
AUTOMATIC DEPENDENT SURVEILLANCE – BROADCAST (ADS-B)
ADS-B is a application to transmit surveillance data from aircraft to ATC ground
stations and between aircraft themselves, and to receive surveillance data from
other aircraft.
Automatic: No action is required from the flight crew.
Dependent: The aircraft provides the surveillance data to the ATC ground station.
The GPS sensor provides aircraft position and speed for ADS-B transmission.
Surveillance: The ATC controller or flight crews from other aircraft use data
broadcast from own aircraft to have a picture of the traffic.
Broadcast: In opposition to Modes A, C, and S operations, ADS-B periodically
transmits surveillance data to the ATC ground station without preliminary
interrogation from a ground station. Compared to ADS-Contract (ADS-C, refer to
2.4 – Aircraft identification and Position Reporting with FANS), ADS-B transmits
surveillance data to the ATC ground station, without specific connection between
the aircraft and the ATC ground station.
•
ADS-B OUT
From the own aircraft perspective, ADS-B OUT refers to the capability to broadcast
(i.e. to transmit without preliminary interrogation) surveillance data. This capability
is part of Mode S transponders installed on AIRBUS aircraft. Refer to 2.2 – Aircraft
Identification and Position Reporting with ADS-B. All Mode S transponders
compliant with ELS and EHS fitted on AIRBUS aircraft are capable of ADS-B OUT.
- 2-6 -
Getting to grips with Surveillance
2 – Aircraft identification and position reporting
•
ADS-B IN
From the own aircraft perspective, ADS-B IN refers to the capability to acquire and
to process surveillance data from other aircraft capable of ADS-B OUT. ADS-B IN is
part of a TCAS capable of ATSAW function, Air Traffic Situational Awareness.
Refer to 3.6 – Description of ATSAW.
2.1.3.8.
EXTENDED SQUITTER
A squitter is an unsolicited transmission. Distance Measuring Equipment (DME)
was the first equipment to use squitters. The ground DME station broadcast
squitters. When the aircraft is in the range of the ground DME station, the airborne
DME unit receives the squitter. Then, the airborne DME unit interrogates the ground
DME station to get the range information. The use of squitters prevents
unnecessary transmissions.
In ADS-B operations, a squitter designates the set of surveillance data broadcast by
a Mode S transponder capable of ADS-B OUT. Squitters from Mode S transponders
are of two types: short (56 bits) or extended (112 bits). The short squitter
contains the aircraft 24-bit address amongst other pieces of information
(communication protocol information on 32 bits). The extended squitter contains
in addition, but not limited to:
- Longitude, latitude, barometric altitude, GPS height, surveillance status, etc.
- Movement, ground track, etc.
- Aircraft identification, flight number, aircraft category, etc.
- GPS velocity, vertical rate, etc.
Notes:
• Refer to 2.2.4 – Generic Emergency Indicator for details on the surveillance
status.
• The aircraft category identifies several types of category: From “no
reporting” to surface vehicle or space vehicle.
TCAS also uses the short squitter (also called acquisition squitter) from Mode S
transponder. The own aircraft TCAS listens to short squitters from surrounding
aircraft Mode S transponders to detect surrounding aircraft. Surrounding aircraft
are identified with their 24-bit address. When TCAS detects a new surrounding
aircraft (i.e. a new 24-bit address via the acquisition squitters), TCAS starts
selective interrogations and tracking of this new surrounding aircraft. Refer to 3.1.2
– TCAS Principle.
2.1.3.9.
1090 EXTENDED SQUITTER
The 1090 MHz Extended Squitter (1090 ES) is the medium used to transmit
ADS-B data. The reader may find other media to transmit ADS-B data:
- Universal Access Transceiver (UAT): FAA supports it for general aviation.
- VHF Data Link Mode 4 (VDL 4): The Swedish CAA supports VDL 4. However,
as VDL 4 causes interferences with other onboard radio transmitters, AIRBUS
does not support this medium.
- 2-7 -
2 – Aircraft identification and position reporting
Getting to grips with Surveillance
2.1.4.
TRANSPONDER CONTROLS
The transponder operating modes are the following: STBY, AUTO, ON. In
addition, the flight crew may set the altitude reporting function to OFF or ON.
In AUTO mode, when the aircraft is on ground, the transponder inhibits Modes A
and C replies and Mode S All Call replies. But Selective Mode S replies and
squitters are still active.
Tips: TCAS switching to STBY
When the flight crew set the transponder to STBY or the altitude reporting to
OFF, the TCAS switches to its STBY mode (i.e. green TCAS STBY memo on EWD,
no TCAS information 4 on PFD and ND). Indeed, the TCAS is not able to determine
the vertical separation with the intruder and then not able to evaluate the
maneuver to avoid the threat. Refer to 3.1.4 – Collision Threat Evaluation.
For more details, please refer to your FCOM.
Several ATC/TCAS panels are available for A300/A310/A320/A330/A340 aircraft.
An airline may choose one single ATC/TCAS panel for all its entire fleet regardless
of the transponder model. Figure 2-2 gives an example of ATC/TCAS panel. Other
ATC/TCAS panels are illustrated at http://www.gableseng.com/platform.asp.
Note: The flight crew must not
confuse the transponder STBY
mode with the TCAS STBY
mode. Refer to Safety First
Magazine, Edition #4, June 2007
“Do you know your ATC/TCAS
panel?” (See AIRBUS References):
Figure 2-2: Example of ATC/TCAS panel
On board an aircraft departing from London Heathrow, a serious incident
occurred. The flight crew switched the transponder STBY. The aircraft became
invisible to ATC radar beacon. The flight crew confuses the TCAS STBY mode with
the XPDR STBY mode, following an ECAM procedure (TCAS MODE ……STBY).
2.2.
AIRCRAFT IDENTIFICATION AND POSITION REPORTING WITH ADS-B
The objectives of aircraft identification and position reporting with ADS-B are to:
- Provide surveillance services where SSR does not exist. There are some areas
where the weak air traffic does not justify the installation of SSR. However, the
provision of surveillance services may greatly improve the air traffic
management.
4
Except for A380 ND where a white indication TCAS STBY is displayed when TRAF is selected on
EFIS.
- 2-8 -
Getting to grips with Surveillance
-
2 – Aircraft identification and position reporting
Decommission redundant SSR installations. Indeed, several SSR may cover a
same airspace, especially near international boundaries. The use of ADS-B
instead of SSR should reduce ATC charges.
The benefits of ADS-B upon SSR are:
- Cost effectiveness: as the ADS-B receiver is far less complex than the SSR
(e.g. the ADS-B receiver does not have any moving parts contrary to SSR with
a rotating antenna), an ADS-B receiver costs ten time less than a SSR
- Better surveillance quality thanks to GPS position 5 and higher refresh rate
(ADS-B: 0.5 s, SSR: 5 s)
- Improved traffic situational awareness in the cockpit thanks to ADS-B IN
applications (refer to 3.6 – Description of ATSAW)
- Reduced electro-magnetic pollution thanks to the use of squitters.
Contrary to SSRs, ADS-B receivers do not emit any signals. In addition,
emissions from SSRs are more powerful than the ones from aircraft.
Figure 2-3: Secondary Radar (left) and
Primary Radar (right)
Figure 2-4: ADS-B ground receiver
Any ATC ground stations equipped with ADS-B receivers are able to collect data
broadcast by surrounding ADS-B aircraft. There are three types of ADS-B service
according to the area where the ADS-B service is provided: in non-radar areas,
in radar areas, on airport surfaces. These new services are part of the
European CASCADE program and will be deployed progressively over the
European airspaces (refer to Appendix A – Worldwide ADS-B implementation).
Similar programs are in progress in USA and Australia. The following sections
describe the ADS-B services as per the European CASCADE program.
2.2.1.
ADS-B SURVEILLANCE IN NON-RADAR AREAS (ADS-B NRA)
The ADS-B-NRA service provides surveillance services in areas where radar
surveillance currently does not exist. It is applicable to airspace classes A to G.
The most famous example is the deployment of ADS-B over the entire Australian
upper airspace (refer to
http://www.airservicesaustralia.com/pilotcentre/projects/adsb/adsbuap.asp).
5
As a dependent surveillance method, ADS-B transmits the aircraft GPS position to the ground.
- 2-9 -
2 – Aircraft identification and position reporting
Getting to grips with Surveillance
The ADS-B NRA service provides a cost effective solution to achieve benefits in
terms of capacity, efficiency and safety in a similar way as it could be achieved
with an SSR.
For more details, please refer to
http://www.eurocontrol.int/cascade/public/standard_page/ads_b_nra.html.
EASA certified A320/A330/A340 aircraft at the beginning of 2008 and
A380 aircraft at the end of 2007 eligible for ADS-B NRA operations.
However, operators must obtain an operational approval from their
Authorities before starting ADS-B NRA operations. Refer to 2.6.2 –
Operational Approval of ADS-B OUT.
2.2.2.
ADS-B SURVEILLANCE IN RADAR AREAS (ADS-B RAD)
The ADS-B-RAD service enables to decommission redundant SSRs and to provide
the same level of surveillance service in areas where radar surveillance currently
exists. It applies to en-route and terminal phases of flight in airspace classes A
to E.
The application improves safety and reduces surveillance costs through the
replacement of some SSRs with ADS B receivers.
Note: The European CASCADE program defines the ADS-B RAD service
areas with high traffic density and the ADS-B NRA service for areas with
low traffic density. Therefore, for the ADS-B RAD service, ATC ground stations
will still use a minimum number of SSR as backup. The use of ADS-B ground
receivers combined with a minimum number of SSR is more cost-effective than an
exclusive set of SSR.
For more details, please refer to
http://www.eurocontrol.int/cascade/public/standard_page/RAD.html
At the time of writing the brochure, Eurocontrol and industrial partners work on
standards for the provision of the ADS-B RAD service.
2.2.3.
ADS-B SURVEILLANCE ON AIRPORT SURFACES (ADS-B APT)
The ADS-B APT service provides ATC controllers with a new surveillance tool of
movements on airport surface. It covers aircraft and ground vehicles equipped
with an ADS-B emitter. The ADS-B APT service may be used as either a
supplement or substitute for existing ground installations (e.g. Surface Movement
Radar – SMR).
At the time of writing the brochure, Eurocontrol and industrial partners work on
standards for the provision of the ADS-B APT service.
- 2-10 -
Getting to grips with Surveillance
2 – Aircraft identification and position reporting
The ADS-B lexicon
ADS-B, as a new technology, brings its set of new terms. The most commonly used
when talking about ADS-B are the following. Technical terms may not be of
operational interest but may be useful during discussions with engineers.
2.2.4.
GENERIC EMERGENCY INDICATOR
The Generic Emergency Indicator is an element of ADS-B messages, coded on two
bits. It provides the Surveillance Status that can be either:
- No change of the SQWK code, or
- Emergency condition (each time 7500, 7600, or 7700 is set on the transponder
control panel), or
- Change in SQWK code (each time a new code different from 7500, 7600 or 7700
is set). This Surveillance Status is active for 18 seconds following the SQWK
code change, or
- SPI condition (when the IDENT function is activated). This Surveillance Status is
active for 18 seconds following the IDENT function activation.
The Generic Emergency Indicator does not indicate either the nature of the
emergency or the SQWK code.
2.2.5.
DISCRETE EMERGENCY CODES
The Discrete Emergency Code is an element of ADS-B messages, coded on three
bits. It provides the nature of the emergency and/or urgency:
- Emergency modes:
o General emergency
o Communication failure
o Unlawful interference
- Urgency modes:
o Minimum fuel
o Medical.
Note: At the time of writing this brochure, only the ACSS XS 950 (P/N 751-780010100) and T3CAS are able to transmit the Discrete Emergency Code.
2.2.6.
DO-260 AND DO-260A
DO-260 “Minimum Operational Performance Standards for 1090 MHz Automatic
Dependent Surveillance – Broadcast (ADS-B)” defines the standards for ADS-B
application. DO-260A is a revision of DO-260.
From an operational view, the main differences are that DO-260 requires the
transmission of the Generic Emergency Indicator and Discrete Emergency
Codes. And DO-260A requires, in addition, the transmission of the transponder
SQWK code. This latter requirement would permit a smooth transition from SSR to
ADS-B operations for ATC controllers as they are used to working with SQWK
codes.
- 2-11 -
2 – Aircraft identification and position reporting
Getting to grips with Surveillance
From a technical point of view, the main differences, in addition to the ones quoted
above, are that DO-260 requires the transmission of the Navigational Uncertainty
Category (NUC), whereas DO-260A requires the Navigation Integrity Category
(NIC), the Navigational Accuracy Category (NAC) and the Surveillance Integrity
Level (SIL) instead of NUC. Appendix E – NUC, NAC, NIC, SIL provides the ranges
of these values.
2.2.7.
GEOGRAPHICAL FILTERING OF SQWK CODE
When surveillance experts defined the ADS-B transmissions at the beginning, two
philosophies stood out: the US American one supporting the need for the
transmission of the SQWK code (for a some transition from SSR to ADS-B
operations), and the European one seeing no need for SQWK code.
Consequently, the industry had decided at that time the SQWK code to be
transmitted through ADS-B only over the USA territory. Outside USA airspaces, the
SQWK code was not transmitted. This was the Geographic Filtering of SQWK code
defined in DO-260A.
At the time of writing the document, the European philosophy has been revised
considering the usefulness of SQWK codes in ADS-B transmissions. Consequently,
DO-260 A Change 2 abolishes the Geographic Filtering of SQWK code.
2.2.8.
VERSION NUMBER
The Version Number is required as per DO-260A and identifies the format of ADS-B
messages. Version Number 0 (or when no version number is transmitted) refers to
DO-260 and Version Number 1 to DO-260A. Version Number 2 is expected for DO260B.
2.2.9.
RECEIVER AUTONOMOUS INTEGRITY MONITORING (RAIM) / FAULT
DETECTION AND EXCLUSION (FDE)
The RAIM/FDE function performs a monitoring of the GPS position integrity. It
measures the confidence in the correctness of the parameters provided by the GPS
constallation. It enables the detection and, when possible, the exclusion of a faulty
satellite. A GPS receiver is able to perform the RAIM/Fault Detection (FD)
function when 5 satellites are visible (4 satellites enables the calculation of a 3D
position; the 5th satellite enables the fault detection).
The FDE function is an enhanced version of RAIM. In addition to the fault
detection, FDE is able to exclude the faulty satellite. As a consequence, the
navigation can rely on GPS satellites without interruption. To that end, the FDE
function requires 6 satellites (4 satellites for the 3D position, 1 satellite for the fault
detection and 1 for the exclusion).
It has to be noted that the FDE function is able to detect and exclude one and
only one faulty satellite. If a second satellite fails, it may be detected but it may
not be excluded.
- 2-12 -
Getting to grips with Surveillance
2 – Aircraft identification and position reporting
2.2.10.
GPS HORIZONTAL FIGURE OF MERIT (HFOM)
HFOM defines the estimated accuracy of the GPS position assuming there is no
satellite failure. HFOM is the radius of a circle centered on the current
position, such that the probability of the actual position lying inside the
circle is 95% or more (or outside the circle with a probability of 5% or less). The
higher the HFOM, the lower the estimated accuracy in the GPS position.
HFOM is also known as Estimated Position Uncertainty (EPU) 6.
2.2.11.
GPS HORIZONTAL PROTECTION LIMIT (HPL)
HPL is the radius of a circle centered on the current position, which defines
an area that is assured to contain the indicated horizontal position with a
given probability.
HPL is also known as Horizontal Integrity Limit (HIL).
HFOM reflects the estimated
accuracy
of
a
satellite
geometry
whereas
HPL
indicates
its
estimated
integrity. Figure 2-5 illustrates
a satellite geometry with:
- A good accuracy (HFOM)
thanks to satellite A
- A poor integrity (HPL) due
to satellite A.
Figure 2-5: Accuracy (HFOM) vs. integrity (HPL)
Indeed, the satellite A position relative to satellites B, C, D reduces the satellite
range errors. The satellite A upgrades the accuracy (HFOM). The high correlation
between satellites B, C and D allows an easy detection of failure from any of these
three satellites. Conversely, the position of satellite A cannot be correlated with
other satellites. Consequently, a failure of satellite A may not be detected. The
satellite A downgrades the integrity (HPL).
2.2.12.
SELECTIVE AVAILABILITY (SA)
The US Department of Defense introduced an artificial error (Selective
Availability) into satellite data to downgrade the accuracy of a GPS position to
100 m for civilian users. Without SA, the accuracy of GPS position can reach down
to 10 m.
On May 1st 2000, the US Department of Defense switched SA off after an
announcement of the US president Bill Clinton.
6
It is different from the Estimated Position Error (EPE) calculated by FM computers. EPE is the drift of
the FM position.
- 2-13 -
2 – Aircraft identification and position reporting
Getting to grips with Surveillance
To make the most of the possible accuracy of the GPS system, the GPS sensor
must include the SA Awareness function. It takes into account that SA is off and
provides more realistic estimates of HFOM and HPL. At the time of writing the
brochure, Thalès MMR only is capable of SA Awareness function. Other GPS sensors
installed on AIRBUS aircraft assume that SA is always on: the accuracy of the GPS
position is always downgraded on a conservative basis.
2.2.13.
NAVIGATIONAL UNCERTAINTY CATEGORY (NUC)
DO-260 defines NUC to characterize both the accuracy and the integrity of
ADS-B data. NUCP is relative to the position, and NUCR to the velocity. The higher
the NUC, the higher the quality of ADS-B data.
NUCP may be derived from HFOM or HPL as per DO-260. However, as illustrated in
Figure 2-5, it is preferable to derive NUCP from HPL to take into account a potential
satellite failure (as HFOM assumes there is no satellite failure). Transponders
proposed on AIRBUS aircraft derive NUCp from HPL first, then from HFOM is HPL is
not available.
2.2.14.
NAVIGATION INTEGRITY CATEGORY (NIC)
DO-260A segregates the accuracy and the integrity of ADS-B data, and defines
the NIC instead of the DO-260 NUC integrity information. NIC is derived from
HPL and defines the same circle as HPL does. HPL is a radius whereas NIC a
category.
2.2.15.
NAVIGATIONAL ACCURACY CATEGORY (NAC)
The DO-260A NAC takes the place of the DO-260 NUC accuracy
information, and is derived from HFOM. NAC defines the same circle as HFOM
does. HFOM is a radius and NAC is a category.
NACP is relative to the position and NACV
to the velocity.
2.2.16.
SURVEILLANCE
INTEGRITY
LEVEL (SIL)
SIL is the probability that the current
position is outside the circle defined by
NIC.
The higher the NIC, NAC and SIL, the
higher the quality of ADS-B data.
Figure 2-6 illustrates the differences
between HFOM, HPL, NIC, NAC, and SIL.
Figure 2-6: NIC, NAC, SIL
- 2-14 -
Getting to grips with Surveillance
2 – Aircraft identification and position reporting
2.2.17.
ADS-B CONTROLS AND INDICATIONS
For the General Aviation community, transponder and ADS-B transmitter are most
of the time separate units. Consequently, pilots can independently operate
transponder and ADS-B transmissions. For the Air Transport Aviation community,
transponder and ADS-B transmitter are merged in a single unit: the transponder
Mode S capable of ADS-B OUT.
Per design, it had been elected to make ADS-B transmissions totally transparent
to the flight crew on AIRBUS aircraft. Consequently, there are neither new
controls nor new indications related to the ADS-B OUT transmissions
addressed to the flight crew. The main benefits are the avoidance of heavy
modifications (e.g. no new connections with other systems, no change on
ATC/TCAS panel) and a minimum impact on cockpit procedures.
In ADS-B operations, the flight crew uses the same controls of the
ATC/TCAS panel for the transmission of the SQWK code 7, IDENT (SPI),
and the barometric altitude as in SSR operations (see Figure 2-2).
In Appendix B – ADS-B phraseology, some instructions refer to the separate
transponder/ADS-B transmitter architecture. When ATC advises such instructions
(e.g. STOP ADS-B TRANSMISSION), refer to AIP for alternate procedures.
On AIRBUS aircraft, if the flight crew switches off the transponder or the
altitude reporting, it cuts off the transmission of ADS-B data or ADS-B altitude
respectively. In addition, it has a major impact on SSR and TCAS operations
(e.g. disappearance from controller SSR scope, non coordinated TCAS maneuver,
surrounding aircraft equipped with TCAS not able to detect and track own aircraft).
2.3. AIRCRAFT IDENTIFICATION AND POSITION REPORTING WITH WIDE
AREA MULTILATERATION
As more and more new systems derived from the CNS/ATM concept 8 come into
the daily operational field, the reader may hear about Multi-lateration. At first
sight, it seems to be another engineering slang word. It is, and the following is a
general description to demystify the Wide Area Multi-lateration (WAM – Multilateration technique applied in wide surveillance areas).
The Multi-lateration technique uses the same principle as the localization of a
mobile phone with ground stations (i.e. triangulation).
Different ground antennas receive a signal from the aircraft. Each antenna
receives the signal at different time due to the relative distance between the
antenna and the signal emitter. A central processing unit connected to the ground
7
Only some transponders capable of ADS-B are capable to transmit the SQWK code. Refer to 2.2.6 –
DO-260 and DO-260A.
8
Refer to Part I of the Getting to Grips with FANS, issue III, April 2007 for a description of the
CNS/ATM concept.
- 2-15 -
2 – Aircraft identification and position reporting
Getting to grips with Surveillance
antennas calculates the aircraft position from the Time Difference Of Arrival
(TDOA) of the signal at the different ground antennas.
With
2
antennas,
the
TDOA
corresponds to a 3D hyperboloid on
which the aircraft is located. The
calculation of the 3D aircraft position
requires 4 antennas. The central
processing
unit
calculates
the
intersection of the 3 hyperboloids. A
configuration with more than 4
antennas permits to calculate an
average
position
with
a
higher
accuracy.
Figure 2-7: Intersection of hyperboloids
The determination of a 3D position with
a 3-antenna configuration requires an
additional source (e.g. barometric
altitude from Mode C transponder
reply)
for
the
aircraft
altitude.
However, the resulting position is less
accurate than the one determined with
a configuration of 4 antennas.
The Multi-lateration technique may be either passive (by listening transmissions
from the transponder like ADS-B OUT) or active (by interrogating the aircraft like
ELS/EHS).
Many signals from the aircraft are available (e.g. SSR, Mode S, DME, etc). The
following characteristics drive the choice of the signal:
- The capability of the signal to provide the aircraft identification
- The availability of the signal
- The quality of the signal.
To fulfill the aircraft identification and position reporting functions, the use of
transponder and ADS-B signals appear the most appropriate solution. The
minimum avionics equipage would be a Mode A/C transponder for active Multilateration technique. The embodiment of Mode S transponder or ADS-B avionics
would enable the passive Multi-lateration technique.
The Multi-lateration technique covers all flight phases (i.e. airborne and surface
movements). The Multi-lateration technique presents roughly the same
advantages than the surveillance based on ADS-B (e.g. coverage of all flight
phases, use in areas where the costs of a radar installation is not justified, etc). In
addition, the Multi-lateration technique allows the detection of aircraft only
equipped with Mode A/C transponders. However, the Multi-lateration technique
requires more ground stations than ADS-B. Some airports (e.g. London Heathrow)
already use the Multi-lateration technique.
For more details, please refer to
- 2-16 -
Getting to grips with Surveillance
2 – Aircraft identification and position reporting
http://www.eurocontrol.int/surveillance/public/standard_page/sur_WAMevent.htm
l or to the Wide Area Multi-lateration Report from the Dutch National
Aerospace Laboratory (NLR) (see References).
2.4.
AIRCRAFT IDENTIFICATION AND POSITION REPORTING WITH FANS
FANS A/A+ systems (namely ATSU for A320/A330/A340 aircraft and ATC
applications for A380 aircraft) host the Automatic Dependent Surveillance –
Contract application, whereas Mode S transponders hosts ADS-B OUT.
The ADS-C application is quite different from the ADS-B application. The ADS-C
application is only used for ATC purposes, contrary to ADS-B that serves the
traffic awareness for both ATC and aircraft capable of ADS-B IN.
The ADS-C application provides surveillance data to map the traffic on ATC
controller’s screen in areas that are not covered by SSR (i.e. oceanic and remote
areas). The ADS-C application takes the place of SSR in those areas but they are
not comparable. Indeed, the ADS-C application reports the aircraft position and its
intents according to conditions (i.e. contract) fixed by the ATC controller. The ATC
controller can set up a periodic, on-event (e.g. when the aircraft sequences a
waypoint) or on-demand (i.e. at ATC controller’s discretion) contract. When the
ATC controller sets up a periodic contract, the ADS-C application reports the
aircraft position on a periodic basis between 15 and 30 minutes. Therefore, the
ATC controller cannot use ADS-C to provide the same separation as with SSR.
OPS+
Nevertheless, ADS-C removes the requirement for tiring HF voice position
reporting. ADS-C makes also the aircraft eligible for long-range
operations with reduced separations (i.e. lateral and longitudinal separations
reduced to 50 NM or 30 NM).
The ADS-C coverage is larger than the SSR one thanks to the FANS technology
(i.e. a data link through satellites or HF, and ACARS network connects aircraft to
ATC centers).
For more details, please refer to the Getting to grips with FANS brochure (see
AIRBUS References).
2.5.
OPERATIONAL RECOMMENDATIONS FOR TRANSPONDER
This paragraph of operational recommendations is intentionally non-exhaustive. For
more recommendations, please check your FCOM and/or FCTM as they are more
frequently updated.
2.5.1.
2.5.1.1.
CONVENTIONAL TRANSPONDER OPERATIONS
FOR THE AIRLINE
Refer to 3.2 – Operational Recommendations for TCAS.
- 2-17 -
2 – Aircraft identification and position reporting
2.5.1.2.
•
•
•
2.5.2.1.
•
•
•
•
OPS+
ADS-B OPERATIONS
FOR THE AIRLINE
Make sure that your flight crews are familiar with ADS-B (e.g.
technology, phraseology, routine and emergency procedures as published in
AIP, etc). Refer to (see References):
o Eurocontrol Flight Crew Guidance for Flight Operations in
ADS-B only Surveillance Airspaces.
o Airservices Australia Flight Operations Information Package
and CASA Pilot Information Booklet.
Ensure that the operational documentation (AFM, MEL, FCOM) is
correctly updated.
Ensure that the aircraft 24-bit address is correctly set in avionics.
Instead of the flight number filled in the ICAO flight plan, ANSP may use the
24-bit address to correlate the aircraft with its logged flight plan. The 24-bit
address is delivered with the aircraft registration number. The operator should
periodically check the 24-bit address and when the State of registration
changes.
Refer to the ADS-B OUT Capability Declaration to support the operational
approval process. Refer to 2.6.2 – Operational Approval of ADS-B OUT.
Refer to OIT 999.0057/08/BB (See AIRBUS References).
2.5.2.2.
•
FOR THE FLIGHT CREW
In normal operations, set the transponder to AUTO and the altitude
reporting function to ON. Transponder settings affect TCAS operations.
Be sure not to confuse controls when operating the ATC/TCAS control
panel. Refer to Safety First Magazine, Edition #4, June 2007 “Do you know
your ATC/TCAS panel?” (See AIRBUS References).
Refer to Part III, Section 3, Chapter 1 of Aircraft Operations – Flight
Procedures, ICAO Doc 8168-OPS/611, Volume I for guidelines related to
transponder operations (see References).
2.5.2.
•
Getting to grips with Surveillance
FOR THE FLIGHT CREW
Make sure that the flight number in the FMS INIT A page matches the
flight number filled in the item 7 of the ICAO flight plan. Use ICAO
format (i.e. three-letter code), do not use IATA format (i.e. two-letter
code). Refer to Appendix 2 of ICAO Doc 4444 – PANS ATM (see
References).ANSP systems are able to process ICAO format only. The flight
number is up to seven characters long. Do not add any leading zeros,
dashes or spaces. According to the FMS standard on board, it may not be
possible to modify the flight number when airborne.
Note: With the first generation of FMS, the flight crew cannot change
the flight number when the aircraft is airborne. The in-service
experience shows that frequent errors are made when entering the
flight number into the avionics worldwide. And ATC controllers detect
the errors when the aircraft is airborne. Consequently, the new
generation of FMS permits to easily change the flight number when
- 2-18 -
Getting to grips with Surveillance
2 – Aircraft identification and position reporting
airborne. The capable FMS standard are the Honeywell FMS2 P2
onwards and the Thalès FMS2 Rev2 onwards.
•
•
Insert “CODE/” followed by the 24-bit address (hexadecimal format)
in item 18 of the ICAO flight plan as required by local requirements.
Declare ADS-B capability in the ICAO flight plan by inserting “/D” in
item 10. “/D” designates the ADS capability (either ADS-C or ADS-B). Local
Authorities may require the insertion of “RMK/ADS-B” in item 18 to clearly
identify the ADS-B capability. Please refer to AIP.
Note:
•
•
•
•
At the time of writing the brochure, ICAO has been reviewing the
coding of equipment carried on-board, including ADS-B. The new
codes are expected to be in force in 2012.
Be sure to master ADS-B procedures (e.g. principles, coverage,
terminology, phraseology, regional – normal and emergency – procedures).
Refer to Appendix A – Worldwide ADS-B implementation and Appendix B –
ADS-B phraseology for more information.
Note that with ADS-B surveillance in non-radar areas (NRA), according to the
type of transponder on board, the ATC controller may not be able to identify
the type of emergency you may encounter (i.e. 7500, 7600 or 7700). Refer to
AIP for applicable procedures. See also 2.2.5 – Discrete Emergency Codes and
2.2.6 – DO-260 and DO-260A.
To preserve SSR or TCAS operations, do not switch off transponder or
altitude reporting when instructed to stop transmitting ADS-B data or
ADS-B altitude (see 2.2.17 – ADS-B Controls and Indications and Appendix B
– ADS-B phraseology).
For more information, refer to (see References):
o Eurocontrol Flight Crew Guidance for Flight Operations in
ADS-B only Surveillance Airspaces.
o Airservices Australia Flight Operations Information Package
and CASA Pilot Information Booklet.
2.6.
REGULATIONS FOR TRANSPONDER
The interpretation of regulations in this paragraph is limited to AIRBUS aircraft at
the time of writing this brochure.
2.6.1.
CARRIAGE OF TRANSPONDER
The carriage of transponder capable of Mode C is mandatory in all ICAO member
States as per ICAO Annex 6 – Operations of Aircraft – Part I:
“6.19.1 All aeroplanes shall be equipped with a pressure-altitude reporting
transponder which operates in accordance with the relevant provisions of Annex
10, Volume IV.
- 2-19 -
2 – Aircraft identification and position reporting
Getting to grips with Surveillance
6.19.2 All aeroplanes for which the individual certificate of airworthiness is first
issued after 1 January 2009 shall be equipped with a data source that provides
pressure-altitude information with a resolution of 7.62 m (25 ft), or better.
6.19.3 After 1 January 2012, all aeroplanes shall be equipped with a data source
that provides pressure-altitude information with a resolution of 7.62 m (25 ft), or
better.
6.19.4 Recommendation. The Mode S transponder should be provided with the
airborne/on-the-ground status if the aeroplane is equipped with an automatic
means of detecting such status.”
As per EASA EU OPS 1.866, a transponder capable of Mode C is mandatory and
other transponder capabilities may be required for the route being flown. At the
time of writing this brochure, the carriage of Mode S ELS transponder is
mandatory in the entire European airspace, and the carriage of Mode S EHS
transponder is mandatory in the core area of Europe (i.e. Belgium, France,
Germany, Luxembourg, The Netherlands, Switzerland and the United Kingdom) as
per the Eurocontrol Specimen AIC – Carriage and Operation of SSR Mode S
Airborne Equipment in European Airspace (see References). The mandate will
be extended to the whole European airspace later on.
As per FAA FAR 121.356, a Mode S transponder is mandatory.
Note: TCAS compliant with TCAS II Change 7 requires a Mode S transponder for
its functioning. Therefore, the mandatory carriage of TCAS (refer to 3.3 –
Regulations for TCAS) implies a mandatory carriage of a Mode S transponder.
2.6.2.
OPERATIONAL APPROVAL OF ADS-B OUT
AIRBUS obtained the EASA airworthiness certification for ADS-B NRA on the A320
family aircraft, the A330/A340 family aircraft and the A380 aircraft. The AFM
states the ADS-B NRA capability. At the time of writing the brochure, four
circulars on ADS-B NRA airworthiness approval were identified (see References):
- The European AMC 20-24 – Certification Considerations for the Enhanced
ATS in Non-Radar Areas using ADS-B Surveillance (ADS-B-NRA) Application
- The Australian AC 21-45 – Airworthiness Approval of Airborne Automatic
Dependent Surveillance Broadcast Equipment
- The Canadian AC 700-009 – Automatic Dependent Surveillance - Broadcast
- The US NPRM Automatic Dependent Surveillance—Broadcast (ADS–B) Out
Performance Requirements to Support Air Traffic Control (ATC) Service.
Agreements between EASA, CASA Australia, Transport Canada permit the
recognition of the European AMC 20-24 in Australia and Canada for ADS-B NRA.
Indeed, the European AMC 20-24 is the most restrictive circular. Consequently,
A320/A330/A340/A380 aircraft, certified as per the European AMC 20-24, are
eligible for ADS-B NRA operations in Australia and Canada. Transponders compliant
with DO-260 are eligible for ADS-B NRA operations.
- 2-20 -
Getting to grips with Surveillance
2 – Aircraft identification and position reporting
The FAA expects to release the final rule based on its NRPM by the end of 2009. It
encompasses demanding ADS-B performance requirements for the 2020
milestone of the Surveillance and Broadcast Services program (refer to Appendix
A – Worldwide ADS-B implementation). The NPRM aims at ADS-B RAD services. At
the time of writing the brochure, a lot of discussions about the NPRM were in
progress. Updated information will be provided in a timely manner.
Operators must obtain an operational approval before starting ADS-B
NRA operations. Eurocontrol outlines some guidelines for the operational
approval process at
http://www.eurocontrol.int/cascade/public/standard_page/guidelines.html
The operational approval covers the following items (but not limited to):
- Operations manuals: AFM, FCOM and MEL should be updated to reflect the
installation of ADS-B components.
- Flight crew training: flight crews should be familiar with ADS-B in terms of
procedures, phraseology, operating principles and operational requirements
(e.g. flight number format).
- Maintenance: regular checks of ADS-B equipment should be performed
including the verification of the 24-bit address.
Refer to one of the appropriate circulars quoted above for details. In addition,
operators should use the ADS-B OUT Capability Declaration referenced in their
AFM to support their operational approval with authorities. Please contact your
Customer Service Director (CSD) to get a copy of this document.
2.7.
MANUFACTURERS FOR TRANSPONDER
At the time of writing the brochure, three models of transponders are available on
AIRBUS aircraft:
- ACSS XS 950, or
- Rockwell Collins TPR 901, or
- Honeywell TRA 67A.
Figure 2-8 provides a simplified view of the transponder architecture.
XPDR
XPDR
Antenna
Antennas
TCAS
Computer
FMGEC
ADIRU*
Mode
Mode SS
Transponder
Transponder
ATSU*
FCU*
FCU*
GPS
GPS source
source*
ATC/TCAS
Control Panel
* Optional Enhanced
* Surveillance
Figure 2-8: Transponder architecture
- 2-21 -
2 – Aircraft identification and position reporting
Getting to grips with Surveillance
Note 1: The Mode S transponder must receive GPS data in order to broadcast
ADS-B data. The GPS source is either a MMR or a GPS-SU. All MMRs installed on
AIRBUS aircraft and Honeywell GPS-SU are compliant with ADS-B OUT
requirements.
Note 2: The Mode S transponder gets pure GPS data via ADIRU. Only hybrid
ADIRUs are able to connect to a GPS source. Therefore, Mode S transponders
connected to autonomous ADIRU cannot get GPS data for ADS-B transmissions.
Mode S transponders connected to autonomous ADIRU always send a NUC = 0
(i.e. integrity is not known as the aircraft position is not based on GPS).
2.7.1.
ACSS XS 950
The ACSS XS 950 transponder (P/N 751-7800-10005) is compliant with DO-260
and the European AMC 20-24. The latest version of XS 950 (P/N 751-780010100) is compliant with DO-260A Change 2 and the European AMC 20-24. This
latter transponder is directly linked to the GPS source in order to improve the
ADS-B OUT performances (e.g. latency).
More information is available at http://www.acssonboard.com/.
2.7.2.
TRANSPONDER PART OF ACSS T3CAS
The ACSS T3CAS is a further step of integration including:
- A Mode S transponder capable of ADS-B NRA as per DO-260A Change 2
- A TCAS II compliant with TCAS II Change 7.1
- An enhanced TAWS module derived from T2CAS TAWS module.
The advantages of this integration are the same as for T2CAS, a step further:
reduced weight, volume, wiring, and power consumption.
The TCAS module and the Mode S transponder module share the same set of
antennas, reducing weight and wirings.
The certification of the T3CAS is expected by end 2009. More information is
available at http://www.acssonboard.com/media/brochures/T3CAS.pdf.
2.7.3.
ROCKWELL COLLINS TPR 901
The Rockwell Collins TPR 901 is capable of ADS-B NRA as per DO-260.
More information is available at
http://www.rockwellcollins.com/products/cs/at/avionics-systems/legacyproducts/index.html.
2.7.4.
HONEYWELL TRA 67A
The Honeywell TRA 67 A is capable of ADS-B NRA as per DO-260.
More information is available at http://www.honeywell.com/sites/aero/TCAS.htm.
2.8.
FUTURE SYSTEMS
At the time of writing the brochure, no new transponder is expected on a short
term.
- 2-22 -
Getting to grips with Surveillance
2 – Aircraft identification and position reporting
Please bear in mind…
Description
To reply to SSR interrogations, the transponder operates in three modes:
- Mode A: transmission of SQUAWK code
- Mode C: transmission of barometric altitude
- Mode S: Selective interrogations replied with enriched transmissions.
Transponders are also capable of operating in a broadcasting mode (ADS-B). The
introduction of ADS-B aims at providing a safer and more cost-effective
surveillance service in regard to the traffic growth. The ADS-B technology enables
three surveillance services (based on the ADS-B OUT data flow) as per the
European CASCADE program:
- ADS-B NRA: ADS-B surveillance in Non-Radar Areas with low traffic density
- ADS-B RAD: ADS-B surveillance backed up by SSR with high traffic density
- ADS-B APT: ADS-B surveillance on airport surfaces.
Basic transponders proposed on AIRBUS aircraft are all capable of Mode A/C/S,
ELS/EHS, and ADS-B NRA. At the time of writing the brochure, definitions of
standards for ADS-B RAD and ADS-B APT are in progress.
Operational recommendations
The main recommendations (but non exhaustive) are:
• The use of the ICAO format (three-letter code) for the flight number
• The use of identical flight numbers in the ICAO flight plan and in the
FMS INIT A page
• An appropriate training regarding ADS-B OUT operations
• A special attention to local implementations of ADS-B
• A correct avionics settings (i.e. 24-bit address)
• A careful flight planning (i.e. flight number, surveillance capability, 24bit address).
Refer to 2.5 – Operational Recommendations for Transponder.
Regulations
The carriage of transponder capable of Mode C is mandatory and the
carriage of transponder capable of Mode S is recommended as per ICAO Annex 6
– Operation of Aircraft – Part I. TCAS compliant with TCAS II Change 7 requires a
Mode S transponder for its functioning. Therefore, the mandatory carriage of
TCAS implies a mandatory carriage of a Mode S transponder.
Future systems
At the time of writing the brochure, no new transponder is expected on a short
term.
- 2-23 -
Getting to grips with Surveillance
3 – Traffic surveillance
3. TRAFFIC SURVEILLANCE
Traffic Collision Avoidance System – TCAS
3.1
3.1.1
3.1.2
3.1.2.1
3.1.2.2
3.1.3
3.1.3.1
3.1.3.2
3.1.4
3.1.4.1
3.1.4.2
3.1.5
3.1.7
3.1.7.1
3.1.7.2
3.1.8
3.2
3.2.1
3.2.2
3.3
3.4
3.4.1
3.4.3
3.4.4
3.5
Description of ACAS – TCAS
TCAS Designation
TCAS Principle
Detection Phase
Tracking Phase
TCAS and Mode S
Coordinated Maneuvers
Communication with ATC Ground Stations
Collision Threat Evaluation
Vertical Separation
Time to Intercept (TAU)
TCAS Envelope
TCAS Indications
TCAS Display
TCAS Aural Alerts
TCAS Controls
Operational Recommendations for TCAS
For the Airline
For the Flight Crew
Regulations for TCAS
Manufacturers for TCAS
ACSS TCAS 2000 and T2CAS
Rockwell Collins TTR 921
Honeywell TPA 100A
Future Systems
- 3-1 -
3-3
3-4
3-4
3-5
3-6
3-6
3-6
3-7
3-7
3-8
3-8
3-9
3-12
3-12
3-14
3-17
3-18
3-18
3-19
3-19
3-20
3-20
3-21
3-21
3-21
3 – Traffic surveillance
Getting to grips with Surveillance
Airborne Traffic Situational Awareness – ATSAW
3.6
3.6.1
3.6.2
3.6.2.1
3.6.2.2
3.6.3
3.6.3.1
3.6.3.2
3.6.4
3.6.4.1
3.6.4.2
3.6.5
3.6.5.1
3.6.5.2
3.7
3.7.1
3.7.2
3.8
3.9
3.10
3.10.1
3.10.2
Description of ATSAW
Enriched Traffic Information
ATSAW Applications
On Ground: ATSA
In Flight: ATSA Airborne (ATSA AIRB
ATSAW Envelopes and Filtering Logic
ATSAW Envelopes
Filtering Logic
ATSAW Indications
ND
MCDU
ATSAW Controls
MCDU controls
Traffic Selector
Operational Recommendations for ATSAW
For the Airline
For the Flight Crew
Regulations for ATSAW
Manufacturer for ATSAW
Future Applications
ATSA SURF with OANS
Enhanced Sequencing and Merging Operations
- 3-2 -
3-23
3-24
3-25
3-25
3-25
3-29
3-29
3-29
3-29
3-29
3-32
3-38
3-38
3-39
3-40
3-40
3-40
3-40
3-40
3-41
3-41
3-41
Getting to grips with Surveillance
3 – Traffic surveillance
The Airborne Collision Avoidance System (ACAS), or commonly named
Traffic alert and Collision Avoidance System (TCAS) has fulfilled the Traffic
Awareness function for years. ACAS stands for the ICAO designation.
Based on gained experience from TCAS operations, AIRBUS developed a new AFS
vertical mode (AP/FD TCAS mode). In order to reduce workload and stress of the
flight crew during an RA alert, AFS assists the flight crew with FD or AP.
As the ADS-B technology arises, a new tool to fulfill the Traffic Awareness function
is now available in the cockpit: the Airborne Traffic Situational Awareness
(ATSA or ATSAW, the latter being the AIRBUS designation). The large set of
data supported by ADS-B permits the ATSAW application to provide enhanced
traffic awareness (e.g. heading and flight number of surrounding aircraft) to the
flight crew.
The following chapter describes the Traffic Awareness fulfilled by conventional
TCAS and new ATSAW.
Aircraft Collision Avoidance System - ACAS
3.1.
DESCRIPTION OF ACAS – TCAS
The concept of airborne collision avoidance system appeared in the early 1950s
with the continuous growth of the air traffic at that time. Several midair collisions
lead to the development of TCAS by the FAA in the United States of America.
Concurrently, ICAO had developed the ACAS standards since the early 1980s and
officially recognized ACAS on November 1993. The ICAO Annex 10, Volume IV
describes the ACAS requirements, and the ICAO PANS-OPS (Doc 8168) and
ICAO PANS-ATM (Doc 4444) define the ACAS operational use.
TCAS is a tool that assists the flight crew for the visual acquisition of
surrounding aircraft. The flight crew must not use the TCAS for selfseparation.
TCAS provides indications about surrounding aircraft and especially alerts about
intruders that may jeopardize the safety of the flight. The indications provide the
flight crew with the position of surrounding aircraft relatively to the own aircraft.
The alerts are of two types:
- Traffic Advisories (TA) that inform the flight crew of the position of intruders
- Resolution Advisories (RA) that provide the flight crew with the position of
threatening intruders and instructions to avoid them.
- 3-3 -
3 – Traffic surveillance
Getting to grips with Surveillance
3.1.1.
TCAS DESIGNATION
The ICAO Annex 10, Volume IV defines three types of ACAS functions:
- ACAS I is the first generation of TCAS. ACAS I provides Traffic Advisories
(TA) and proximity warning of surrounding aircraft to assist the flight crew in
the visual acquisition of intruder aircraft. TCAS I is installed in some small
aircraft and helicopters in some regions in the world (e.g. aircraft with less
than 31 and more than 10 passengers in USA). TCAS I is out of the scope of
the present brochure.
- ACAS II is a ACAS I augmented with the capability to provide Resolution
Advisories (RA) in the vertical plane. The development of ACAS II started in
the early 1990s. Several standards (or Changes) have been defined and the
latest one is known as TCAS II Change 7.1 or Version 7.1. The TCAS II
Change 7.1 is compliant with ICAO Standards and Recommended Practices
(SARPs) for ACAS II. ICAO mandated the carriage of ACAS II Change 7.0 since
2003 (since 2000 in Europe). At the time of writing the brochure, the TCAS II
Change 7.1 was released. ICAO intends to mandate the TCAS II Change 7.1
from 2012 (refer to 3.1.6 – TCAS II Change 7.1).
- ACAS III is intended to provide TA and RA in both vertical and horizontal
planes. At present, no ACAS III system has been developed, and none is likely
to appear in the near future due to technical and operational difficulties.
The level of protection provided by TCAS depends of the transponder capability of
surrounding aircraft.
Surrounding
aircraft
Own aircraft
ACAS I
ACAS II
Mode A XPDR
TA
TA
Mode C or S
XPDR
TA
TA & RA
ACAS I
TA
TA & RA
ACAS II
TA
TA &
Coordinated RA 1
Most equipment installed on AIRBUS aircraft are compliant with TCAS II Change
7. Therefore, TCAS refers to equipment compliant with TCAS II Change 7.0
for the remainder of the document, except when specified.
3.1.2.
TCAS PRINCIPLE
TCAS works autonomously and independently of the aircraft navigation equipment
and ATS ground systems. Therefore, to detect and track any surrounding aircraft,
TCAS periodically interrogates surrounding aircraft transponders.
The interrogation principle is similar to the one for SSR.
1. The own aircraft TCAS interrogates the surrounding aircraft transponder.
11
Both aircraft must be equipped with Mode S transponders for coordinated maneuvers.
- 3-4 -
Getting to grips with Surveillance
3 – Traffic surveillance
2. The surrounding aircraft transponder replies to the own aircraft TCAS with
data provided by the surrounding aircraft TCAS (e.g. RA generated by the
surrounding aircraft TCAS).
Thanks to the interrogation
Surrounding aircraft
principle,
the
TCAS
computes the following
Own aircraft
parameters to determine
XPDR
the collision threat:
- The range between
TCAS
TCAS Interrogation
aircraft by measuring
1030 MHz
the
elapsed
time
XPDR
Reply
between
the
1090
MHz
interrogation and the
Figure
3-1:
TCAS
interrogation
and
reply
transponder reply
2
- The relative altitude with the barometric altitude transmitted by Mode C or
S transponders
- The variations of range and altitude with successive interrogations
- The bearing of surrounding aircraft with the interferometry principle.
Each threat is treated individually but the TCAS determines the best solution of
collision avoidance with respect to all aircraft in its vicinity. At the same time, the
TCAS coordinates maneuvers with other TCAS-equipped aircraft. The best
solution of collision avoidance is the maneuver that ensures an adequate
separation of trajectories with a minimum vertical speed variation.
3.1.2.1.
DETECTION PHASE
TCAS detects surrounding aircraft by regularly listening to acquisition squitters
(refer to 2.1.3.8 – Extended Squitter for more details on squitters) from Mode S
transponders of surrounding aircraft. When TCAS records some 24-bit addresses,
TCAS starts a cyclical process repeated every second:
1. Mode C interrogations to get altitudes of non-Mode S aircraft
2. Mode S interrogations to get altitudes of Mode S aircraft via selective calls
3. Squitter listening.
This principle applies to the detection of aircraft equipped with Mode A or Mode
C transponders. When the own aircraft TCAS interrogates in Mode C:
4. An aircraft equipped with a Mode A transponder, the latter replies with its
SQWK code. TCAS uses this reply for horizontal positioning purpose (i.e.
bearing). TCAS does not process the SQWK code itself,
5. An aircraft equipped with a Mode C transponder, the latter replies with its
standard barometric altitude.
It has to be noticed that own aircraft TCAS only detects surrounding
aircraft with an operative transponder.
2
Mode A transponders does not transmit the barometric altitude. Therefore, the TCAS is not able to
compute the relative altitude from a reply provided by a Mode A transponder, and only triggers a TA for
aircraft equipped with Mode A transponders.
- 3-5 -
3 – Traffic surveillance
3.1.2.2.
Getting to grips with Surveillance
TRACKING PHASE
When TCAS detected surrounding aircraft, TCAS tracks them by series of
interrogations and replies. These exchanges permit the update of the relative
altitude, the range and the bearing for each aircraft, and to determine the
variations of range and altitude. TCAS can track up to 40 aircraft (60 aircraft
for the A380 TCAS function) simultaneously and displays the 8 most
threatening aircraft.
3.1.3.
TCAS AND MODE S
TCAS, Mode S transponders and Mode S ground stations use the same
frequencies to transmit and receive messages. Thanks to this statement, data
exchanged through the Mode S data link allow the coordination of avoidance
maneuvers and the communication between aircraft equipped with TCAS and
Mode S transponder.
The coordination in avoidance maneuvers is only possible with Mode S
equipped aircraft.
3.1.3.1.
COORDINATED MANEUVERS
The coordination of maneuvers prevents the flight path corrections ordered by
each TCAS from resulting in a hazardous situation. It prevents from two aircraft
maneuvering in the same direction (e.g. both aircraft climb) that could lead to a
worse situation.
In most cases of encounters between two TCAS-equipped aircraft, mutual
identification is almost simultaneous. However, there is a sufficient delay to
establish the priorities for the coordination process.
The first aircraft to detect a potentially hazardous situation computes an
avoidance maneuver sense, and communicates it to the other aircraft. The other
aircraft takes the information into account and in turn computes an avoidance
maneuver in the opposite sense.
It may happen that two aircraft simultaneously detect and simultaneously
transmit coordination messages with avoidance maneuvers in the same sense. In
this particular case, the aircraft with the highest 24-bit address reverses the
sense of its avoidance maneuver.
In coordinated maneuvers, only one RA reversal is triggered when
changes in the encounter geometry occur. Therefore, the initial RA is
reversed when:
- The initial RA has been displayed for at least 9 seconds, or
- The aircraft, with the lowest 24-bit address, has a vertical speed greater than
2 500 ft/min (upwards or downwards), and flies in the opposite sense of its
initial RA.
- 3-6 -
Getting to grips with Surveillance
3 – Traffic surveillance
This delay provides the two aircraft with sufficient time to respond to the initial
RA.
For TCAS compliant with TCAS II Change 7.1 (refer to 3.1.6 – TCAS II
Change 7.1), if the aircraft with the highest 24-bit address does not follow its
TCAS order, the coordination of maneuvers gives the priority to the other aircraft
(i.e. with the lowest 24-bit address).
The coordination of maneuvers may be phased as follows:
1. Detection: The own aircraft TCAS listens to squitters.
2. Acquisition: The own aircraft TCAS receives a squitter, and interrogates the
transponder of the intruder identified by the 24-bit address contained in the
squitter. The transponder of the intruder replies with several data including its
barometric altitude.
3. Tracking: The own aircraft TCAS tracks the intruder with regular
interrogations.
4. Coordination: If the intruder becomes a threat, the own aircraft TCAS
computes an avoidance maneuver to avoid a risk of collision. The two aircraft
initiates a coordination procedure with the exchange of a coordination
interrogation and a coordination reply.
3.1.3.2.
COMMUNICATION WITH ATC GROUND STATIONS
When the TCAS triggers an RA, the TCAS is able to report it to Mode S ground
stations. This report informs the ATC controller that the reporting aircraft had
performed an avoidance maneuver.
The flight crew must immediately report any RA to the ATC controller, even
if TCAS is able to report RA to Mode S ground stations.
3.1.4.
COLLISION THREAT EVALUATION
Aircraft are categorized (i.e.
OTHER, PROXIMATE, TA and
RA) according to two criteria:
the vertical separation or
relative altitude (difference of
barometric altitudes) and the
range between aircraft.
Range
Vertical
separation
Figure 3-2: Vertical separation and range
Regular interrogations of surrounding aircraft permit to determine the variations
of the vertical separation and of the range. These variations are called vertical
rate and range rate.
The collision threat evaluation takes into account two criteria determined with
respect to the Closest Point of Approach (CPA). CPA is the point of minimum
- 3-7 -
3 – Traffic surveillance
Getting to grips with Surveillance
range between the aircraft, assuming that their trajectories do not deviate (refer
to Figure 3-3). The two criteria are:
- The vertical separation at CPA
- The time to reach CPA or time to intercept (TAU or τ 3).
3.1.4.1.
VERTICAL SEPARATION
the
vertical
Considering
separation, the range and their
variations for a surrounding
aircraft, the own aircraft TCAS
is able to predict whether the
surrounding aircraft will trigger
a TA or an RA at CPA.
Altitude
T0
T1
T2
Own aircraft
Aircraft 1
CPA
T2
At CPA, three zones are defined
T1
(refer to Figure 3-3). The
vertical separation between the
T0
intruder and own aircraft at CPA
defines the type of advisory to
Aircraft 2
be triggered:
Figure 3-3: Closest Point of Approach (CPA)
- Between T0 and T1: TA
- Between T1 and T2: Preventive RA, it instructs the flight crew to avoid
certain deviations from current vertical speed. A red sector only is displayed on
the Vertical Speed Indicator (VSI)
- Below T2: Corrective RA, it instructs to fly within a vertical speed range,
displayed in green on VSI. A red sector on VSI indicates the forbidden vertical
speed range.
Values of T0, T1 and T2 vary according to TAU values (refer to 3.1.4.2 – Time to
Intercept (TAU)) and the sensitivity level (refer to 3.1.5 – TCAS Envelope).
In Figure 3-3, a corrective RA will be triggered because of Aircraft 1 and a TA will
be triggered because of Aircraft 2.
3.1.4.2.
TIME TO INTERCEPT (TAU)
TCAS determines the collision threat with TAU rather than the geometric position
of CPA. For two aircraft approaching on the same axis, this time is the ratio of the
distance between the aircraft by the sum of their speeds.
TAU =
3
Distance
Range
or more generally TAU =
.
Range rate
VOwn Aircraft + VIntruder
TAU refers to the Greek letter τ.
- 3-8 -
Getting to grips with Surveillance
3 – Traffic surveillance
The collision threat increases when TAU decreases. The TCAS triggers
advisories when TAU crosses predetermined time threshold.
This method based on TAU prevents advisories from being triggered if the TAU
trend is inverted even though the range between two aircraft decreases (e.g.
aircraft of parallel airways in opposite directions illustrated in Figure 3-4).
Figure 3-4 : TAU variation with range
Note: In addition to this check in the horizontal plane, TCAS performs similar
check in the vertical plane (i.e. based on the ratio of relative altitude by the
vertical speeds) for the triggering of a TCAS RA.
3.1.5.
TCAS ENVELOPES
The
surveillance
envelope is divided +9 900 ft
into four volumes:
2 700 ft and 9 900
ft above, 2 700 ft +2 700 ft
and
9
900
ft
below.
The
horizontal
range ALL
may vary from 14
to
100
NM
according to the -2 700 ft
TCAS manufacturer.
Refer to your FCOM
for more details.
-9 900 ft
ABOVE
BELOW
Figure 3-5: TCAS surveillance envelopes
- 3-9 -
3 – Traffic surveillance
Getting to grips with Surveillance
The flight crew can restrict the TCAS display in a given volume. The flight crew
selects the following settings: ALL, ABOVE, or BELOW as per Figure 3-5.
Protection envelopes are also defined to set the threat levels around the
aircraft. There are 4 protection envelopes around the aircraft (from the farthest to
the closest ones): OTHER, PROXIMATE, TA and RA. Refer to Figure 3-8.
The OTHER volume is the volume outside the PROXIMATE volume, from –9900 ft
to +9900 ft, and up to the maximum horizontal range. The PROXIMATE volume
covers the vertical range from –1 200 ft to +1 200 ft, and the horizontal range up
to 6 NM.
The dimensions of TA and RA volumes depend on TAU value. The penetration of
the TA or RA volumes triggers Traffic Advisories or Resolution Advisories
respectively. TAU varies according to the own aircraft altitude and the TCAS
sensitivity level. The higher the own aircraft altitude and the sensitivity level, the
higher the time to intercept TAU.
The sensitivity level permits a balance between necessary protection and
unnecessary advisories. The sensitivity level goes from 1 to 7:
- Level 1 when TCAS is set in STAND BY, failed or the aircraft is on ground. In
level 1, TCAS does not transmit any interrogations
- Level 2 when TCAS is set in TA ONLY mode (RA are inhibited)
- Levels 3 to 5 automatically selected according to the own aircraft altitude
when TCAS is in TA/RA mode.
Example: For own aircraft altitude from 5 000 to 10 000 ft, the sensitivity level
is SL5 and TAU for TA is 40 seconds and TAU for RA is 25 seconds.
For more details, please refer to Introduction to TCAS II Version 7 (see
References).
3.1.6.
TCAS II CHANGE 7.1
The TCAS II Change or Version 7.1 is the result of a workshop composed of DSNA
(French Air Navigation Service Directorate) and Egis Avia experts, and sponsored
by Eurocontrol. The TCAS II Change 7.1 introduces two major changes:
- The Change Proposal 112E (CP112E) about the reversal logic
- The Change Proposal 115 (CO115) related to the RA “ADJUST VERTICAL
SPEED, ADJUST”.
3.1.6.1.
CP112E – SOLUTION TO THE REVERSAL LOGIC ISSUE
In the TCAS II Change 7.0, an issue has been identified that leads to nonissuance of reversal RA in specific situations. Indeed, in the TCAS II Change 7.0,
when the vertical separation is less than 100 ft, the TCAS does not trigger
reversal RA. This issue is also known as the “100 ft box” issue.
- 3-10 -
Getting to grips with Surveillance
3 – Traffic surveillance
This issue has been observed in several in-service events. The geometry is always
the same: both aircraft are either descending or climbing. The issue has been
identified in:
- The accident that occurred in January 2001 in Japan where several passengers
were injured. Both aircraft got near to each other approximately by less than
180 m (600 ft) laterally and less than 60 m (200 ft) vertically.
- The collision of Uberlingen over the Lake Constance in July 2002. All
passengers and crewmembers were killed.
In both events, the ATC controller had instructed one of the aircraft to maneuver
in the opposite direction as ordered by TCAS.
The CP112E introduces a monitoring of the compliance to RA. When the own
aircraft does not follow the RA and goes in the opposite direction for a certain
time, the “100 ft box” rule is inhibited: reversal of RA is then possible when
aircraft get vertically closer than 100 ft.
In addition, the CP112E predicts the vertical separation at CPA, taking into
account current vertical speeds. When aircraft are predicted to get nearer than
below a given threshold, reversal of RA is authorized for aircraft vertically nearer
than 100 ft.
Latencies in RA reversals are tailored in order to make the most of initial RA (RA
reversal not too early) and to avoid additional RA reversals (too late RA
reversals).
3.1.6.2.
ISSUE
CP115 – SOLUTION TO THE “ADJUST VERTICAL SPEED, ADJUST”
The RA “ADJUST VERTICAL SPEED, ADJUST” is always an order to reduce
the vertical speed. Most of the time, an opposite reaction to such an RA leads to
a significant reduction of the vertical separation with the intruder and a significant
augmentation of the collision risk.
A large number of unintentional opposite reactions to this RA has been observed.
The main causes identified are:
- The lack of training on the particular RA “ADJUST VERTICAL SPEED, ADJUST”
- The lack of explicit indications in the RA “ADJUST VERTICAL SPEED, ADJUST”
- The difficulties to interpret VSI indications.
To simplify the procedure, the CP115 replaces the RA “ADJUST VERTICAL
SPEED, ADJUST” by a new RA “LEVEL OFF”. In the TCAS II Change 7.0, there
are currently four RA “ADJUST VERTICAL SPEED, ADJUST” with different vertical
speed targets: 0, 500, 1 000, and 2 000 ft/min. The introduction of the new RA
“LEVEL OFF” (one RA upwards and one RA downwards) make the last three RA
above useless. It reduces the set of RA and simplifies the training.
- 3-11 -
3 – Traffic surveillance
Getting to grips with Surveillance
3.1.7.
TCAS INDICATIONS
In addition to aural alerts, PFD, ND, and EWD display TCAS indications. The ND
provides the surrounding aircraft position. The PFD provides the avoidance
maneuver orders. EWD provides memos and warnings relative to the TCAS.
3.1.7.1.
TCAS DISPLAY
Navigation Display – ND
3.1.7.1.1.
- When TCAS is able to acquire the bearing of surrounding aircraft, the
ND displays surrounding aircraft according to their threat category (i.e.
OTHER, PROXIMATE, TA or RA).
- For surrounding aircraft equipped with Mode A transponder, the ND
displays the surrounding aircraft according to their bearing and range only.
- For surrounding aircraft equipped with Mode C or S transponder, the
ND displays the surrounding aircraft according to their bearing, range, vertical
separation and vertical speed trend.
- When TCAS is not able to acquire the bearing (e.g. multi-path
propagation) of surrounding aircraft, the ND displays a literal indication
only (e.g. 5.01 NM +01 ↓). The literal indication includes the range, the
vertical separation in hundreds of feet and the vertical speed trend. The same
color-coding applies as the one used for graphical indications.
The TCAS display on ND is available in ROSE and ARC modes. See Figure 3-7.
3.1.7.1.2.
Primary Flight Display – PFD
When TCAS is able to order an
avoidance maneuver (i.e. with
intruder equipped with Mode C or
S transponder), on the Vertical
Speed Indicator (VSI):
- The green sector is the safe
range of vertical speed (FLY
TO sector)
- The red sector is strictly
forbidden.
Figure 3-6: TCAS display on PFD
- 3-12 -
Getting to grips with Surveillance
3 – Traffic surveillance
OTHER aircraft
PROXIMATE aircraft
TA intruder
RA intruder
Vertical speed
trend
Vertical separation
(x 100ft)
2.5 NM range ring
Figure 3-7: TCAS display on ND
RA
TA
Proximate
Other
Figure 3-8: TCAS protection envelopes
Note: TA and RA volumes are based on time (TAU values) instead of distance.
- 3-13 -
3 – Traffic surveillance
Getting to grips with Surveillance
3.1.7.1.3.
Engine and Warning Display – EWD
When the flight crew sets the
TCAS to STBY, the ALT RPTG
to OFF, or the XPDR to STBY
from the ATC/TCAS panel, the
green memo TCAS STBY is
displayed on EWD.
3.1.7.2.
TCAS AURAL ALERTS
TA and RA TCAS displays come with aural alerts. On A300/A310/A320/A330/A340
aircraft, the Flight Warning System (FWS) broadcasts these aural alerts through
the loudspeakers, and the flight crew cannot modify their volume. On A380
aircraft, the FWS broadcasts the aural alerts through the loudspeakers and the
headsets.
3.1.7.2.1.
Traffic Advisory
Aural alerts
TRAFFIC TRAFFIC
Meaning
TCAS detects a TA aircraft.
3.1.7.2.2.
Resolution Advisory
For all the aural alerts listed below, the TCAS detects an RA aircraft, and is able to
order avoidance maneuvers (with intruder equipped with Mode C or S
transponder).
Meaning
Required
V/S (ft/min)
CLIMB, CLIMB
Climb at a vertical speed in the
green sector on PFD.
+1 500
CLIMB, CROSSING CLIMB,
CLIMB, CROSSING CLIMB
Climb at a vertical speed in the
green sector on PFD.
The own flight path will cross
through the intruder’s one.
+1 500
INCREASE CLIMB,
INCREASE CLIMB
Increase the vertical speed to
climb.
It is triggered after a CLIMB
advisory.
+2 500
CLIMB, CLIMB NOW,
CLIMB, CLIMB NOW
Invert the vertical speed from
DESCENT to CLIMB.
It is triggered after a DESCEND
advisory when a reversal in sense is
required to achieve a safe vertical
+1 500
Aural Alerts
- 3-14 -
Getting to grips with Surveillance
3 – Traffic surveillance
Aural Alerts
Required
V/S (ft/min)
Meaning
separation
intruder.
from
a
maneuvering
DESCEND, DESCEND
Descent at a vertical speed in
the green sector on PFD.
-1 500
DESCEND, CROSSING
DESCEND, DESCEND,
CROSSING DESCEND
Descent at a vertical speed in
the green sector on PFD.
The own flight path will cross
through the intruder one.
-1 500
INCREASE DESCENT,
INCREASE DESCENT
Increase the vertical speed to
descent.
It is triggered after a DESCENT
advisory.
-2 500
DESCEND, DESCEND NOW,
DESCEND, DESCEND NOW
Invert the vertical speed from
CLIMB to DESCENT.
It is triggered after a CLIMB
advisory when a reversal in sense is
required to achieve a safe vertical
separation from a maneuvering
intruder.
-1 500
ADJUST VERTICAL SPEED,
ADJUST
(Removed if TCAS II Change
7.1 implemented)
LEVEL OFF
(TCAS II Change 7.1 only)
Reduce the vertical speed to fly
the green sector on PFD.
It is a corrective reduce climb or
reduce descent, or a weakening of
corrective RA.
Set the vertical speed to 0.
It
replaces
the
RA
ADJUST
VERTICAL SPEED, ADJUST. Refer to
3.1.6.2 – CP115 – Solution to the
“ADJUST
VERTICAL
SPEED,
ADJUST” Issue.
Climb
Min 0
Max +2 000
Descent
Min 0
Max –2 000
0
Monitor the vertical speed so as
to remain out of the red sector.
MONITOR VERTICAL SPEED It is a preventive advisory. The
TCAS calculated a forbidden vertical
speed range (red sector).
MAINTAIN VERTICAL
SPEED, MAINTAIN
Maintain
speed.
the
- 3-15 -
current
vertical
Climb
Min +1 500
Max +4 400
Descent
Min –1 500
Max –4 400
3 – Traffic surveillance
Getting to grips with Surveillance
Aural Alerts
Meaning
MAINTAIN VERTICAL
SPEED, CROSSING
MAINTAIN
CLEAR OF CONFLICT
Maintain the current vertical
speed.
The own flight path will cross
through the intruder one.
Required
V/S (ft/min)
Climb
Min +1 500
Max +4 400
Descent
Min –1 500
Max –4 400
Calm down.
The collision threat disappeared.
3.1.7.2.3.
Aural Alert Priority
The FWS prioritizes aural alert with other systems as follows:
1. Wind shear alert or stall alert
2. TAWS alerts
3. TCAS alerts.
In
-
case of wind shear, stall, or GPWS warnings:
FWS inhibits TCAS aural alerts
TCAS converts all RAs into TAs on ND
TCAS automatically sets the TA ONLY mode.
3.1.7.2.4.
Advisory Inhibition
When the own aircraft is below an altitude limit ± margin (+ in climb, - in
descent), the TCAS automatically activates some inhibition logics.
Altitude limit
Inhibition
Above 48000 ft MSL
RA CLIMB CLIMB is inhibited to preserve aircraft performances.
Above 15500 ft MSL
TCAS does not interrogating Mode A aircraft or Mode C aircraft
without altitude information (when ALT RPTG of these aircraft
is set to OFF). However, TCAS still interrogates Mode S aircraft
even they do not report their altitude.
Below 1700 ft AGL
The Ground logic is activated: any aircraft operating in Mode
C only that are below 380 ft AGL (relative to the own aircraft,
see Figure 3-9) are declared on ground. See note below.
Below 1550 ft AGL
RA INCREASE DESCENT is inhibited.
Below 1100 ft AGL
RA DESCENT is inhibited.
Below 1000 ft AGL
TA ONLY is automatically activated.
Below 500 ft AGL
TA aural alerts are inhibited.
Note: The ground logic only applies to surrounding aircraft that operate in Mode
C. Mode S aircraft transmit an explicit indication when airborne or on ground.
- 3-16 -
Getting to grips with Surveillance
3 – Traffic surveillance
Figure 3-9: TCAS inhibitions
3.1.8.
TCAS CONTROLS
The flight crew selects the TCAS operating modes via two different switches as
follows:
- STBY: TCAS inhibits aural and visual indications. The EWD displays the green
TCAS STBY memo.
- TA: TCAS converts all RAs in TAs (aural and visual alerts). The ND displays the
white TA ONLY message.
- TA/RA: TCAS operates normally.
- THRT: TCAS displays OTHER or PROXIMATE aircraft on ND only if the TCAS
already displays a TA or RA aircraft.
- ALL: TCAS displays surrounding aircraft in the surveillance envelope between
–2 700 ft and +2 700 ft (refer to Figure 3-5).
- ABV: TCAS displays surrounding aircraft in the surveillance envelope between
–2 700 ft and +9 900 ft (refer to Figure 3-5).
- BLW:. TCAS displays surrounding aircraft in the surveillance envelope between
–9 900 ft and +2 700 ft (refer to Figure 3-5).
Figure 2-2 gives an example of ATC/TCAS panel.
- 3-17 -
3 – Traffic surveillance
Getting to grips with Surveillance
Tips: TCAS switching to STBY
When the flight crew sets the TCAS to STBY, the transponder to STBY, or
the altitude reporting to OFF, TCAS switches to its STBY mode (i.e. green TCAS
STBY memo on EWD, no TCAS information 4 on PFD and ND). Indeed, TCAS is not
able to interrogate intruders or to determine the vertical separation with the
intruder. Therefore, TCAS is not able to evaluate the threat. Refer to 3.1.4 –
Collision Threat Evaluation.
For more details, please refer to your FCOM.
3.2.
OPERATIONAL RECOMMENDATIONS FOR TCAS
This paragraph of operational recommendations is intentionally non-exhaustive. For
more recommendations, please check your FCOM and/or FCTM as they are more
frequently updated.
It is highly recommended to consult the ACAS II bulletins from Eurocontrol
to set and maintain a proper safety level in TCAS II operations at
http://www.eurocontrol.int/msa/public/standard_page/ACAS_ACAS_Safety.html.
The Eurocontrol ACAS II bulletins analyze in-service incidents/accidents and
provide
recommendations
that
prevent
the
occurrences
of
such
incidents/accidents. Some of the following recommendations are extracted from
the Eurocontrol ACAS II bulletins, available at the time of writing the brochure.
3.2.1.
FOR THE AIRLINE
• Recurrently train your flight crews to use TCAS and to respond to RA
safely and efficiently (especially responses to RA “ADJUST VERTICAL SPEED,
ADJUST”).
• Refer to ICAO Doc 9863 – Airborne Collision Avoidance System (ACAS)
Manual and Part III, Section 3, Attachment of Chapter 3 of Aircraft
Operations – Flight Procedures, Doc 8168-OPS/611, Volume I for pilot
training guidelines (see References).
• Insure that the XPDR altitude reporting is accurate. Inaccurate altitude
reporting may lead to unnecessary RA with potential domino effect in RVSM
airspaces.
4
Except for A380 ND where a white indication TCAS STBY is displayed when TRAF is selected on
EFIS.
- 3-18 -
Getting to grips with Surveillance
3.2.2.
3 – Traffic surveillance
FOR THE FLIGHT CREW
•
Always follow the RA even when there is:
- An opposite ATC instruction, as the maneuver may be coordinated with
the intruder, or
- A traffic information from ATC, as the refreshing rate of the SSR scope
may not be quick enough to depict precisely the actual situation, or
- An order to climb when flying in the vicinity of the maximum
aircraft ceiling, as a small margin to climb is better than a descent, or
- A visual acquisition, as an aircraft could be wrongly identified.
•
React immediately and appropriately. The RA order must be applied
without delay and the green sector of the vertical speed scale must not be
exceeded. Do not overreact.
Do not change the flight path on TA alert. TA is not a dangerous collision
threat. However, pay attention when a TA is triggered.
ADJUST VERTICAL SPEED = Reduce vertical speed. Do not invert the
maneuver.
Take care of VFR traffic whose transponder may not transmit the
barometric altitude. Indeed, Mode C at least is required to trigger RA.
Do not use the TCAS to maintain separations with other aircraft. The
ATC controller is responsible for the separation of aircraft. In addition, the
TCAS does not provide enough information as SSR does to insure a safe
separation.
Report RA to ATC as soon as possible. This might be the only way to
inform the ATC controller of an RA. It will prevent the ATC controller issuing
conflicting instructions.
Always report to ATC when clear of conflict as soon as possible. This
might be the only way the ATC controller has to resume normal operations.
Resume initial ATC clearance when clear of conflict.
Limit vertical speed to 1 500 ft/min during the last 2 000 ft of the
climb or descent. It will prevent level busts that could lead to conflict with
aircraft above or below the cleared flight level, especially in RVSM airspaces.
Check that TCAS is active while approaching a runway for take-off. An
active TCAS at that time enables to check there is no landing traffic before
lining up on the runway and to prevent omissions of TCAS activation for takeoff.
Refer to ICAO Doc 9863 – Airborne Collision Avoidance System (ACAS)
Manual and Part III, Section 3, Chapter 3 of Aircraft Operations – Flight
Procedures, Doc 8168-OPS/611, Volume I for operational guidelines (see
References).
•
•
•
•
•
•
•
•
•
•
3.3.
REGULATIONS FOR TCAS
The interpretation of regulations in this paragraph is limited to AIRBUS aircraft at
the time of writing this brochure.
The carriage of ACAS II as per ICAO Annex 10, Volume IV is mandatory in all
ICAO member States as per ICAO Annex 6 – Operations of Aircraft – Part I:
- 3-19 -
3 – Traffic surveillance
Getting to grips with Surveillance
“6.18.1 From 1 January 2003, all turbine-engined aeroplanes of a maximum
certificated take-off mass in excess of 15 000 kg or authorized to carry more than
30 passengers shall be equipped with an airborne collision avoidance system
(ACAS II).
6.18.4 An airborne collision avoidance system shall operate in accordance with the
relevant provisions of Annex 10, Volume IV.”
As per EASA EU OPS 1.668, ACAS II is mandatory.
As per FAA FAR 121.356, ACAS II is mandatory.
3.4.
MANUFACTURERS FOR TCAS
At the time of writing the brochure, three models of TCAS II are available on
AIRBUS aircraft:
- ACSS TCAS 2000 or the T2CAS with TCAS module, or
- Rockwell Collins TTR 921, or
- Honeywell TPA 100A.
Figure 3-10 provides a simplified view of the TCAS architecture.
TCAS
TCAS
Antenna
Antenna
Radio
Radio
Altimeter
Altimeter
FMGEC
FMGEC
TCAS
Computer
Mode
ModeSS
Transponder
Transponder
ADIRU
ATC/TCAS
Control Panel
Figure 3-10: TCAS architecture
3.4.1.
ACSS TCAS 2000 AND T2CAS
From ACSS, the TCAS 2000 and the T2CAS are available on AIRBUS aircraft to
fulfill the traffic awareness function. The TCAS part of the T2CAS is almost
identical to the ACSS TCAS 2000. The minor differences only affect the
maintenance functions.
More information is available at http://www.acssonboard.com/.
- 3-20 -
Getting to grips with Surveillance
3 – Traffic surveillance
3.4.2.
TCAS PART OF ACSS T3CAS
The ACSS T3CAS is a further step of integration including:
- A Mode S transponder capable of ADS-B OUT as per DO-260A Change 2
- A TCAS II compliant with TCAS II Change 7.1
- An enhanced TAWS module derived from T2CAS TAWS module.
The advantages of this integration are the same as for T2CAS, a step further:
reduced weight, volume, wiring, and power consumption.
The TCAS module and the Mode S transponder module share the same set of
antennas, reducing weight and wirings.
The certification of the T3CAS is expected by end 2009. More information is
available at http://www.acssonboard.com/media/brochures/T3CAS.pdf.
3.4.3.
ROCKWELL COLLINS TTR 921
From Rockwell Collins, the TTR 921 is available on AIRBUS aircraft. It is a
component of the Rockwell Collins ACAS 900 suite.
More information is available at
http://www.rockwellcollins.com/products/cs/at/avionics-systems/legacyproducts/index.html.
3.4.4.
HONEYWELL TPA 100A
From Honeywell, the TPA 100A is available on AIRBUS aircraft. The latest version
of TPA 100A (P/N 940-0351-001) is compliant with TCAS II Change 7.1.
More information is available at http://www.honeywell.com/sites/aero/TCAS.htm.
3.5.
FUTURE SYSTEMS
At the time of writing the brochure, no new TCAS is expected on a short term.
- 3-21 -
3 – Traffic surveillance
Getting to grips with Surveillance
Please bear in mind…
Description
TCAS as per TCAS II Change 7.0 fulfills the Traffic Surveillance function. It
provides Traffic Advisories (TA), Resolution Advisories (RA), even
coordinated RA when own aircraft and intruders are equipped with Mode S
transponders.
TCAS II Change 7.1 introduces a new reversal logic and replaces the RA
“ADJUST VERTICAL SPEED, ADJUST” by a new RA “LEVEL OFF”.
Most TCAS available on AIRBUS aircraft comply with TCAS II Change 7.0: ACSS
TCAS 2000 or T2CAS, Rockwell Collins TTR 921, Honeywell TPA 100A (P/N 9400300-001). ACSS T3CAS and Honeywell TPA 100A (P/N 940-0351-001) complies
with TCAS II Change 7.1.
Operational recommendations
The main recommendations (but non exhaustive) are:
• The cognizance of Eurocontrol ACAS II bulletins
• An appropriate and recurrent training on TCAS
• The conformation to RA in any cases without delay
• The adequate response to TCAS aural alerts (e.g. ADJUST VERTICAL
SPEED, no flight path change based on TA only, no excessive reaction to
RA)
• The unreliability of TCAS for aircraft self-separation
• The immediate report to ATC in case of RA and when clear of conflict
• The conformation to the initial ATC clearance when clear of conflict.
Refer to 3.2 – Operational Recommendations for TCAS.
Regulations
The carriage of TCAS II is mandatory as per ICAO Annex 6 – Operation of
Aircraft – Part I.
Future systems
At the time of writing the brochure, no new TCAS is expected on a short term.
- 3-22 -
Getting to grips with Surveillance
3 – Traffic surveillance
Airborne Traffic Situational Awareness - ATSAW
The aim of ATSAW is to improve the traffic awareness of the flight crew thanks to
ADS-B. ATSAW is one of those steps that implement new systems to improve the
air traffic management. One of the long-term objectives would be the aircraft selfseparation. As a first step, ATSAW is limited to the traffic awareness. In addition,
it has to be noted that ATSAW is part of a new TCAS computer but it does
not address the aircraft collision avoidance. The ACAS part of the TCAS
computer still ensures the aircraft collision avoidance.
The concept of ATSAW includes several applications that are optimized for each
flight phase (on ground or airborne). AIRBUS already proposes systems capable of
airborne ATSAW applications (refer to 3.6.2 – ATSAW Applications) and plans to
cover all applications. Manufacturers that propose TCAS computer capable of
ATSAW are:
- Honeywell with a new version of TPA 100A: At the time of writing the
brochure, the certification is expected very shortly (mid 2009)
- ACSS with its T3CAS: The certification of ACSS T3CAS is planned for the end
2009.
Note: For the remainder of the document:
- ATSAW function refers to as a part of the airborne system.
- ATSAW applications refer to the operational use of the ATSAW function in a
given context.
3.6.
DESCRIPTION OF ATSAW
The Airborne Traffic Situational Awareness (ATSAW 5) function displays
traffic information to the flight crew like a TCAS. However, the main differences
are:
- The ATSAW function listens to ADS-B messages broadcast by
surrounding aircraft. The ATSAW function is also called ADS-B IN function
(refer to Figure 3-11 and 2.1.3.7 – Automatic Dependent Surveillance –
Broadcast (ADS-B)). The ATSAW function displays only surrounding aircraft
equipped with an ADS-B OUT emitter that operates on 1090 MHz (e.g. Mode S
EHS transponder capable of ADS-B OUT).
- The ATSAW traffic information is enriched. Compared to TCAS traffic
information, the ATSAW function provides in addition, but not limited to, the
flight identification, the orientation, the speed and the wake vortex category of
surrounding aircraft (refer to 3.6.1 – Enriched Traffic Information).
- The ATSAW function do not provide any alerts. For collision avoidance
purposes, the flight crew must refer to TCAS indications.
5
ATSAW is the AIRBUS designation. ATSA is the ICAO standard designation.
- 3-23 -
3 – Traffic surveillance
Getting to grips with Surveillance
The ATSAW function is a tool that assists the flight crew for the visual
acquisition of surrounding aircraft capable of ADS-B OUT. The flight crew
must not use the ATSAW function for self-separation and collision
avoidance.
A new TCAS computer
supports
the
ATSAW
function. Therefore, TCAS
and ATSAW information are
seamlessly
integrated
(refer
to
3.6.4.2.4
–
Combination of TCAS and
ADS-B Information).
The new TCAS computer
still provides TA and RA
when aircraft separations
are
not
sufficient.
In
addition,
it
provides
enriched information to the
flight crew thanks to the
ATSAW function.
Surrounding aircraft
Own aircraft
XPDR ADS-B Out
ADS-B In TCAS
TCAS ADS-B In
ADS-B ground
receiver
ADS-B Out XPDR
ADS-B data flow
Figure 3-11: ADS-B data broadcast and collection
TCAS computer capable of ATSAW
The introduction of the ATSAW function into the TCAS computer does not change
TCAS operations. The new TCAS computer triggers TA and RA (ACAS function) in
the same way as a conventional TCAS computer does. However, the TCAS
computer capable of ATSAW is compliant with TCAS II Change 7.1. Refer
to 3.1.6 – TCAS II Change 7.1 for more details.
ACAS and ATSAW software are fully segregated inside the TCAS computer.
3.6.1.
ENRICHED TRAFFIC INFORMATION
As a reminder, a conventional TCAS is able to
and the relative altitude of intruders within 30
ACAS – TCAS). The TCAS computer capable of
messages up to 100 NM behind and ahead of
either side of the aircraft.
determine the range, the bearing
NM (refer to 3.1 – Description of
ATSAW is able to listen to ADS-B
the aircraft, and up to 30 NM on
Thanks to the information available in the Extended Squitter (refer to 2.1.3.8 –
Extended Squitter), the ATSAW function provides for any surrounding aircraft
capable of ADS-B OUT:
- The heading
- The flight number 6
- The position
- The ground speed
- The relative altitude
- The indicated air speed
- The vertical tendency
- The wake vortex category.
- The distance
6
Refer to Appendix F for details.
- 3-24 -
Getting to grips with Surveillance
3 – Traffic surveillance
3.6.2.
ATSAW APPLICATIONS
The following sections describe the different ATSAW applications. At the time of
writing the brochure, the ATSAW function on AIRBUS aircraft is capable of ATSA
AIRB, ITP and VSA applications. Some details on ATSAW applications can also be
found at
http://www.eurocontrol.int/cascade/public/standard_page/service_descriptions.ht
ml.
3.6.2.1.
ON GROUND: ATSA SURFACE (ATSA SURF)
ATSA SURF provides the flight crew with information regarding the surrounding
traffic during taxi and runway operations. ATSA SURF is expected to improve
safety and to reduce taxi time during low visibility conditions and by night.
3.6.2.2.
IN FLIGHT: ATSA AIRBORNE (ATSA AIRB)
ATSA AIRB provides the flight crew with information regarding the surrounding
traffic when in flight. ATSA AIRB is expected to improve the traffic awareness and
the safety in flight.
ATSA AIRB is a general use of ATSAW when the aircraft is airborne. ATSA AIRB
supplements the verbal traffic information from the ATC controller and
flight crews of surrounding aircraft. Therefore, ATSA AIRB is expected to
improve the flight safety and efficiency thanks to improved traffic awareness. In
particular, the flight crew uses ATSA AIRB to enhance existing procedures:
- Construction of traffic awareness
- Visual acquisition for See-and-Avoid
- Traffic Information Broadcasts by Aircraft (TIBA).
The benefits of ATSA AIRB are:
• An optimization and/or reduction of workload. With a better
knowledge of the traffic situation, the flight crew is able to manage and
anticipate tasks. ATSAW AIRB also reduces the mental effort to construct
the traffic awareness.
• A reduction of radio communication. With a better knowledge of the
traffic situation, the flight crew will request fewer updates of traffic
information or fewer clearances blocked by surrounding aircraft (e.g.
request for a flight level already occupied by another aircraft).
• A reduction of useless RA. With a better knowledge of the traffic
situation, the flight crew will reduce the vertical speed when the aircraft
approaches the cleared flight level. A high vertical speed when the aircraft
approaches the cleared flight level may trigger useless RA. Refer to 3.2 –
Operational Recommendations for TCAS.
• Early detection of developing dangerous situations. With a better
knowledge of the traffic situation, the flight crew can identify dangerous
situations with other aircraft and contact the ATC controller to get
confirmation.
- 3-25 -
3 – Traffic surveillance
•
Getting to grips with Surveillance
More cooperative responses from flight crews to ATC instructions.
With a better knowledge of the traffic situation, the flight crew can better
understand and accept ATC instructions.
3.6.2.2.1.
Construction of Traffic Awareness
With the existing procedure, the flight crew mentally constructs the traffic picture
thanks to
- The transmissions of the ATC controller and other flight crews on a given radio
frequency
- Visual scans regularly performed out the window.
However, these methods present some limiting factors:
o Surrounding aircraft are not necessarily on the same frequency (e.g.
departure and arrival frequencies).
o The deployment of Controller Pilot Data Link Communication (CPDLC)
reduces the amount of information available in the party line.
o The visual scans are limited in front of and above the own aircraft.
o The visual scans provide a rough estimate of the range, the relative
altitude, and the vertical tendency.
o Instrument Meteorological Conditions (IMC) limit the visual scans.
ATSAW AIRB improves the construction of traffic awareness as:
- It detects all aircraft capable of ADS-B OUT around the own aircraft.
- It is more precise than visual scans for the location of surrounding aircraft.
- It does not depend of the meteorological conditions.
- It reduces the mental effort of the flight crew to construct the traffic picture.
3.6.2.2.2.
Visual Acquisition for See-and-Avoid
The See-and-Avoid procedure mainly relies on the visual acquisition of
surrounding aircraft. However, the flight crew hardly achieves the visual
acquisition of an aircraft because:
o Aircraft that fly VFR are often small, and aircraft that fly IFR are
bigger but faster.
o An aircraft on a collision course remains on a constant bearing. The
flight crew hardly detects the threat due to the lack of apparent
relative movement.
o In busy flight phases (e.g. approach), the flight crew may
inadvertently reduce the time for visual scans due to the workload
increase.
o The windshield limits the visual scans. Some dead angles appear in
specific aircraft attitude (e.g. during a turn).
o The flight crew may wrongly identify an aircraft through visual scans.
ATSAW AIRB improves the visual acquisition for See-and-Avoid as:
- It provides a precise location of surrounding aircraft.
- It provides the flight number (when available) of each aircraft.
- 3-26 -
Getting to grips with Surveillance
3 – Traffic surveillance
3.6.2.2.3.
Traffic Information Broadcasts by Aircraft (TIBA)
The Traffic Information Broadcasts by Aircraft (TIBA) is applied in areas where:
- Radar surveillance is low or absent, or
- Communications are not reliable, or
- Air Traffic Services are not reliable.
The TIBA objective is the collision avoidance instead of separation provision.
Therefore, in TIBA airspaces, a flight crew may perform a collision avoidance
maneuver based on TIBA reports listened on the radio frequency. In this context,
the flight crew makes again a significant mental effort to construct the traffic
picture. In addition, in TIBA airspaces, it is for collision avoidance purposes. Refer
to Attachment C of ICAO Annex 11 (see References) for details about the TIBA
procedure.
Collision avoidance with TIBA
The collision avoidance with TIBA occurs far beyond the threshold of a TCAS RA.
The time scale for the collision avoidance with TIBA is some minutes. The time
scale for the collision avoidance with TCAS is less than 1 minute.
In TIBA airspaces, the flight crew considers there is a collision risk when another
aircraft is:
o At the same flight level or is going to climb/descent through the
flight level of the own aircraft
o Converging on the same route or estimating to pass a point at
almost the same time as the own aircraft.
ATSA AIRB improves the TIBA procedure as:
o It reduces the mental effort of the flight crew to construct the traffic
picture.
o It permits the flight crew to anticipate any maneuvers for collision
avoidance.
o Some flight crews do not broadcast traffic information on the TIBA
frequency.
3.6.2.3.
IN CRUISE: ATSA IN TRAIL PROCEDURE (ATSA ITP)
ATSA ITP is the use of ATSAW with the In Trail Procedure (ITP). The ITP enables
aircraft in oceanic and remote non-radar airspaces to change flight levels on a
more frequent basis. The benefits of the ITP are:
• A reduction of the fuel consumption by flying the optimum cruise flight
level
• A reduction of emissions by burning less fuel
• An improvement of the flight efficiency by flying flight levels with more
favorable winds
• An improvement of the flight safety by avoiding flight levels with
turbulence
• An increase of the airspace capacity by musical chair sequence: an ITP
aircraft leaving its initial flight level leaves a space for another aircraft.
- 3-27 -
3 – Traffic surveillance
Getting to grips with Surveillance
ATSAW significantly improves the traffic awareness of the flight crew. When the
flight crew applies the ITP with ATSAW, the ATC controller may authorize the
flight crew to climb or descent with temporarily reduced minima of longitudinal
separations in predefined circumstances. Therefore, thanks to the reduced
longitudinal separation minima, flight level changes should be more frequent.
Note: The ATC controller authorizes reduced longitudinal separation minima
during the climb or descent only. The ATC controller re-establishes procedural
longitudinal separation minima when the aircraft reaches the new flight level.
The use of ATSAW with the In Trail Procedure is fully described in
Appendix C – ATSAW In Trail Procedure (ITP).
3.6.2.4.
DURING APPROACH: ATSA VISUAL SEPARATION ON APPROACH
(ATSA VSA)
ATSA VSA (also called Enhanced Visual Separation on Approach) is the use of
ATSAW with the Visual Separation on Approach (VSA) procedure. The VSA
procedure permits the flight crew to maintain a visual separation on the preceding
aircraft during the approach when VMC conditions are met. The visual separation
is shorter than the standard radar separation. Therefore, the benefits of the VSA
procedure are:
• An increase of the airport landing capacity thanks to the shorter
separations between aircraft. The increase is even more significant for
airports that operate closely spaced parallel runways. Indeed, at such
airports, the VSA procedure permits to simultaneously use several arrival
streams with alternation of landings on parallel runways. When the VSA
procedure is suspended, some arrival streams are suspended, and the
airport landing capacity is reduced.
• An increase of the airport take-off capacity. The application of the VSA
procedure permits the insertion of additional take-offs between landings.
• A reduced flight time thanks to the increase of the global airport
capacity.
ATSA VSA eases the application of the VSA procedure in the following terms:
- The flight crew establishes the visual contact with the preceding aircraft in an
easier and more reliable way.
- The flight crew is able to clearly identify the preceding aircraft.
- The flight crew anticipates a speed reduction from the preceding aircraft
thanks to ATSAW and maintains the visual separation with the preceding
aircraft more easily.
In addition, ATSA VSA brings additional benefits to the VSA procedure:
• A reduced probability of wave vortex encounters, as the flight crew is
able to better maintain the visual separation.
• A reduced communication workload for the flight crew and the ATC
controller, as the visual acquisition of the preceding aircraft is easier.
The use of ATSAW with the VSA procedure is fully described in Appendix
D - ATSAW Visual Separation on Approach (VSA).
- 3-28 -
Getting to grips with Surveillance
3.6.3.
3.6.3.1.
3 – Traffic surveillance
ATSAW ENVELOPES AND FILTERING LOGIC
ATSAW ENVELOPES
-
Vertical extension:
o For ACSS T3CAS: The ATSAW envelopes have the same vertical
extension as the TCAS envelopes (refer to Figure 3-5). They depend
on the settings of the TCAS control panel (ALL, ABOVE, or BELOW).
o For Honeywell TCAS TPA 100A: The ATSAW envelope goes from –
10 000 ft to + 10 000 ft, regardless of the settings of the TCAS
control panel.
-
Horizontal range: 100 NM longitudinally, 30 NM on either sides of the
aircraft..
3.6.3.2.
FILTERING LOGIC
The TCAS computer limits the display of traffic (ADS-B and/or TCAS – refer to
3.6.4.1.1 – TCAS and ATSAW Symbols) that are in the ATSAW envelopes:
- On ND: to the 8 closest aircraft (to avoid clutter)
- On MCDU: to 90 aircraft.
3.6.4.
ATSAW INDICATIONS
The ATSAW indications are available on ND and MCDU. The TCAS computer
updates the ATSAW indications every second.
3.6.4.1.
ND
The ND displays the ATSAW traffic information in ARC and NAV modes. The ND
displays the 8 closest aircraft. The ND with ATSAW traffic information is also
called the Cockpit Display of Traffic Information (CDTI).
3.6.4.1.1.
TCAS and ATSAW Symbols
On ND, the TCAS computer capable of ATSAW displays three types of traffic
symbols:
- TCAS Only: The traffic does not transmit ADS-B data. The TCAS computer
identifies the traffic with TCAS data only.
- ADS-B Only: The traffic transmits ADS-B data and is out of TCAS range. The
TCAS computer identifies the traffic with ADS-B data only.
- TCAS+ADS-B: The traffic transmits ADS-B data and is in TCAS range. The
TCAS computer identifies the traffic with both TCAS and ADS-B data. Refer to
3.6.4.2.4 – Combination of TCAS and ADS-B Information.
- 3-29 -
3 – Traffic surveillance
Traffic
Symbol
Getting to grips with Surveillance
Other
Proximate
TA
RA
TCAS Only
ADS-B Only
TCAS+ADS-B
The orientation of ATSAW symbols is the track contained in ADS-B messages.
Thanks to the different ATSAW controls (refer to 3.6.5 – ATSAW Controls), the
ATSAW symbols get different states (refer to Figure 3-12).
The extended label shows
the flight number of the
traffic. The full label shows
the
flight
number,
the
ground speed, and the wake
vortex category (L: Light, M:
Medium, H: Heavy).
Basic
Extended
Full
Figure 3-12: ATSAW symbol labels
Note: The wake vortex category complies with the ICAO PANS-ATM definitions
(see References):
LIGHT – aircraft with a MTOW less than 7 000 kg
MEDIUM – aircraft with a MTOW between 7 000 kg and 136 000 kg
HEAVY – aircraft with a MTOW more than 136 000 kg.
When a piece of information is missing in ADS-B messages (e.g. ground
speed), the piece of information is not displayed on ND.
When the position or the track is not available in ADS-B messages, the
corresponding ATSAW symbol:
- For TCAS+ADS-B: Becomes a TCAS Only symbol.
- For ADS-B Only: Is removed from ND.
Refer also to 3.6.4.2.4 – Combination of TCAS and ADS-B Information for other
cases when ATSAW symbols are not displayed.
A flight crewmember can highlight, select, or both highlight and select an ATSAW
symbol. Refer to 3.6.5.2 – Traffic Selector.
- 3-30 -
Getting to grips with Surveillance
When a flight crewmember
highlights
or
selects
an
ATSAW symbol, the TCAS
computer displays the ATSAW
symbol with its full label.
Refer to Figure 3-13.
3 – Traffic surveillance
Highlighted
Highlighted and
Selected
Selected
Figure 3-13: Highlight and selection of an ATSAW
symbol
Note 1: The TCAS computer displays:
• When it triggers a TA:
o All non-TA aircraft with basic labels (refer to Figure
3-12). If a non-TA aircraft is selected and/or
highlighted, the TCAS computer displays this nonTA aircraft in cyan with basic labels (refer to Figure
3-14).
o The TA aircraft using one of the symbols illustrated
in Figure 3-15 depending the flight crew setting
(selected and/or hightlighted, or not).
Basic
Extended
Full
Selected
Figure 3-14:
Non-TA
aircraft
selected
and/or
highlighted
Highlighted and
Selected
Figure 3-15: ATSAW symbols for TA aircraft
•
•
Non
When it triggers an RA:
Highlighted
Highlighted
o Removes the labels for all aircraft (RA
and non-RA aircraft). Therefore, the
flight crew can easily identify the
intruder.
o Keeps the highlight circle when the
Figure 3-16: ATSAW
highlighted aircraft becomes an RA
symbols for RA aircraft
aircraft.
When Clear of Conflict:
o Reverts all aircraft to their previous state as before the TA or RA
event.
The introduction of the ATSAW function does not modify the ACAS function.
When a TA or RA occurs, apply the conventional TCAS procedures.
- 3-31 -
3 – Traffic surveillance
Getting to grips with Surveillance
Note 2: When an ATSAW symbol is:
• Highlighted and exits the ATSAW envelope and the ND range, the TCAS
computer:
o Removes the highlight signs (cyan circle on ND and cyan brackets on
MCDU)
o Displays the TRAFFIC LIST page on MCDU if the current MCDU page
was the TRAFFIC INFORMATION page (refer to 3.6.4.2 – MCDU).
• Selected and exits the ATSAW envelope and the ND range, the TCAS
computer:
o Maintains the highlight and selection signs (highlight: cyan circle on
ND, cyan brackets on MCDU; selection: cyan labels)
o Maintains the TRAFFIC INFORMATION page on
MCDU
o Displays a half ATSAW symbol on the edge of
the ND display area (e.g. ND edge in ROSE
NAV mode or outermost ring in ARC mode)
Figure 3-17: Half
with the correct bearing.
ATSAW symbol
3.6.4.2.
MCDU
On MCDU, the TCAS computer capable
of ATSAW displays three pages:
- The TRAFFIC LIST page
- The TRAFFIC INFORMATION page
- The ITP TRAFFIC LIST page.
The flight crew can access to these
pages through the TRAF prompt (LSK
5R) in the MCDU MENU.
Figure 3-18: MCDU MENU
3.6.4.2.1.
Traffic List Page
The TRAFFIC LIST page displays up to
90 aircraft that are in the ATSAW
envelopes (refer to 3.6.3.1 – ATSAW
Envelopes). Two sub-lists compose the
Traffic List:
1. The
sub-list
of
aircraft
displayed on ND: flight numbers
are
displayed
with
large
characters.
2. The sub-list of aircraft not
Figure 3-19: Traffic List page
displayed on ND: flight numbers
are
displayed
with
small
characters.
These sub-lists are sorted in alphabetical order. When one aircraft does not
provide its flight number (dashes replace the flight number), the aircraft is located
at the end of the sub-list.
- 3-32 -
Getting to grips with Surveillance
3 – Traffic surveillance
For each aircraft in the Traffic List:
- The flight number and the wake vortex category are displayed. If the wake
vortex category is not available, a blank field replace the wake vortex
category.
- A prompt gives access to details on the aircraft (refer to 3.6.4.2.2 – Traffic
Information Page).
The Traffic List page also:
- Gives access to the ITP Traffic List (IN TRAIL PROCEDURE prompt available
when the ITP option is activated, refer to 3.6.4.2.3 – ITP Traffic List Page)
- Provides two functions (TRAF ON and FLT ID ON, refer to 3.6.5.1 – MCDU
controls).
3.6.4.2.2.
Traffic Information Page
When the flight crew presses one LSK
next to a flight number in the Traffic
List, the MCDU displays the TRAFFIC
INFORMATION page.
The
TRAFFIC
INFORMATION
page
contains the information transmitted by
the given aircraft via ADS-B.
As described in 3.6.4.2.5 – Information
sources for ADS-B traffic, when a piece
Figure 3-20: Traffic Information page
of information is missing in ADS-B
messages, the TCAS is the secondary
source for some pieces of information. The second part of the title line shows the
sources the TCAS computer used to fill in the TRAFFIC INFORMATION page. In
Figure 3-20, the TCAS computer used both ADS-B and TCAS information (see
ADS-B/TCAS indication in the title line).
When a piece of information is not available, dashes replace the piece of
information (except wake vortex category) in the TRAFFIC INFORMATION page.
From the MCDU, the flight crew may
select or deselect (LSK 6R) the aircraft
displayed in the TRAFFIC INFORMATION
page. The TCAS computer accordingly
updates the ND.
The flight crew selects the TRAFFIC LIST
RETURN prompt (LSK 6L) to return to
the TRAFFIC LIST page.
The flight crew can scroll the Traffic List
from the TRAFFIC INFORMATION page
with the MCDU SLEW keys (↑↓).
Figure 3-21: Traffic Information page
with selected aircraft
- 3-33 -
3 – Traffic surveillance
Getting to grips with Surveillance
3.6.4.2.3.
ITP Traffic List Page
The flight crew uses the ITP TRAFFIC
LIST page to initiate the In-Trail
Procedure (refer to Appendix C –
ATSAW In Trail Procedure (ITP) for
details).
The flight crew must enter the desired
FL in the amber boxes (LSK 1L).
The FLT ID ON function (LSK 6R) is
identical to the one available in the
TRAFFIC LIST page (refer to 3.6.5.1 –
MCDU controls).
Figure 3-22: ITP Traffic List page
The flight crew selects the RETURN prompt (LSK 6L) to return to the TRAFFIC
LIST page.
When the flight crew entered the desired FL, the TCAS computer computes the
opportunity to perform an ITP (refer to C.2.5 – ITP Distance). The ITP Traffic List
displays:
- The flight level taken into account for the computation (LSK 1L)
- The opportunity to perform an ITP (LSK 1R)
- The ITP distances to aircraft included in the ITP volume (LSK 3L to 5L, refer to
C.2.5 – ITP Distance and C.2.3 – ITP Volume). The ITP Traffic List displays
only aircraft that are on the same direction (refer toC.2.2 – Aircraft on the
Same Direction).
Figure 3-23: ITP possible
Figure 3-24: ITP possible with detected
non-ADS-B aircraft
The TCAS computer displays the message TRAFFIC AT FLXXX RNGYY (refer to
Figure 3-24) when:
- A surrounding aircraft is within 80 NM and at the desired FL entered in LSK 1L,
or
- There is a TCAS Only aircraft between the current FL and the desired FL, or
- There is an ADS-B Only aircraft on the track at less than 30 NM, or
- 3-34 -
Getting to grips with Surveillance
-
3 – Traffic surveillance
There is an aircraft not on the same direction between the current FL and the
desired FL.
When the ITP is not possible, the TCAS computer provides the reasons that
prevent the ITP:
- Below the in-trail distance (refer to Figure 3-25):
o DISTANCE when the distance criterion is not met, or
o REL SPEED when the relative speed criterion is not met, or
o NO FLT ID when the flight number is not available.
- Next to LSK 2R when there are more than two aircraft in the ITP volume. Refer
to Figure 3-26.
Figure 3-25: ITP not possible due to the
distance with one aircraft
Figure 3-26: ITP not possible due to the
number of aircraft
Note: The ITP Traffic List is sorted as follows:
- When ITP is possible, aircraft are displayed from the farthest one in front of
the own aircraft (e.g. 45 NM BEHIND AZE1597) to the farthest one after the
own aircraft (e.g. 32 NM AHEAD OF VBN8624).
- When ITP is not possible, aircraft that block the ITP procedure are displayed
first.
ITP Traffic List
Last aircraft
First aircraft
VBN8624
AZE1597
32 NM AHEAD OF
45 NM BEHIND
Figure 3-27: Sorting of the ITP Traffic List
- 3-35 -
3 – Traffic surveillance
Getting to grips with Surveillance
The TCAS computer also indicates when the ITP maneuver is in progress (refer to
Figure 3-28), or when a standard procedure instead of ITP is sufficient to perform
a climb or a descent (refer to Figure 3-29).
Figure 3-28: ITP in progress
Figure 3-29: ITP not applicable
3.6.4.2.4.
Combination of TCAS and ADS-B Information
TCAS information is based on TCAS measurements (refer to 3.1.2 – TCAS
Principle). ADS-B information is based on GPS sensor of surrounding aircraft.
Therefore, ADS-B information is supposed to be more accurate than TCAS
information.
The TCAS computer uses the best positioning source for display. Most of the time,
the TCAS computer will use ATSAW information. However, the TCAS computer
do NOT display the ATSAW symbol of a surrounding aircraft on ND (or the
traffic information in the MCDU Traffic List) for the following reasons:
- When ADS-B information is outdated by 3 s, or
- When the position of the surrounding aircraft received by ADS-B differs from
its TCAS position by:
• 0.5 NM in range, or
• 200 ft in altitude, or
• ± 30° in bearing.
- When the surrounding aircraft transmits:
• For surrounding aircraft equipped with a DO-260 transponder: a NUC value
from 0 to 4 inclusive
• For surrounding aircraft equipped with a DO-260A transponder:
- A NIC value between 0 and 5 inclusive, or
- A SIL value between 0 and 1 inclusive, or
- A NAC value between 0 and 5 inclusive.
- When the surrounding aircraft does not transmit its track or position, or
- When the GPS position of the own aircraft is lost for more than 5 min, or
downgraded (HIL higher than 0.5 NM).
The TCAS computer displays the TCAS Only symbol when:
- The TCAS computer does not display the ATSAW symbol for the reasons above
- The TCAS information is available.
- 3-36 -
Getting to grips with Surveillance
3 – Traffic surveillance
3.6.4.2.5.
Information sources for ADS-B traffic
The following table provides the sources of information displayed for ADS-B
traffic.
Information
Primary
source
Secondary
source
Aircraft
identification
ADS-B
N/A
Remarks
The ADS-B traffic position is taken
from GPS sensors of ADS-B traffic.
The ADS-B traffic position is checked
against its TCAS range (refer to C.2.5
– ITP Distance) for the verification of
ADS-B data integrity.
Position
ADS-B
N/A
Wake vortex
category
ADS-B
N/A
IAS
ADS-B
N/A
GS
ADS-B
N/A
Vertical
speed
ADS-B
TCAS
The TCAS function determines the
vertical speed thanks to successive
TCAS interrogations.
TCAS
The TCAS function determines the
relative altitude thanks to the
barometric altitude reported in Mode
C or S.
The TCAS function determines the
altitude thanks to the barometric
altitude reported in Mode C or S.
Relative
altitude
ADS-B
Altitude
ADS-B
TCAS
Heading
ADS-B
N/A
Track
ADS-B
N/A
Bearing
ADS-B
N/A
Calculated from GPS positions of ADSB and own aircraft.
Distance
ADS-B
N/A
Calculated from GPS positions of ADSB and own aircraft. Refer to C.2.5 –
ITP Distance.
When some pieces of information are missing, the TCAS computer displays:
- On ND: Only available information
- On MCDU: Dashes in appropriate fields (except wake vortex category).
The TCAS computer uses the GPS position to locate the own aircraft.
- 3-37 -
3 – Traffic surveillance
Getting to grips with Surveillance
3.6.5.
ATSAW CONTROLS
With ATSAW controls, the flight crew can:
- Highlight and/or select an aircraft on ND
- Display or hide ATSAW symbols on ND
- Display or hide flight numbers for all ATSAW symbols on ND.
The ATSAW controls except the selection function are limited to the own
side ND. The Captain and the First Officer can independently highlight, display, or
hide ATSAW symbols and flight numbers on their own ND. However, when one
flight crewmember selects one aircraft on his ND (with the traffic selector or with
the MCDU TRAFFIC SELECT function), the ND of the other flight crewmember also
displays the selection.
The selected aircraft is a common reference for both flight crewmembers.
3.6.5.1.
MCDU CONTROLS
TRAF ON/OFF
3.6.5.1.1.
The TRAF ON/OFF function in the TRAFFIC LIST page (refer to Figure 3-19)
displays or hides ATSAW symbols on ND.
When the TRAF ON/OFF function is set to OFF, the TCAS computer:
- Removes ADS-B Only symbols from ND
- Replaces TCAS+ADS-B symbols by TCAS Only symbols on ND (refer to
3.6.4.1.1 – TCAS and ATSAW Symbols)
- Permits the display of the Traffic List on MCDU.
The TRAF ON/OFF function affects the own side ND only.
3.6.5.1.2.
FLT ID ON/OFF
The FLT ID ON/OFF in the TRAFFIC LIST and the ITP TRAFFIC LIST pages (refer to
Figure 3-19 and Figure 3-22) displays or hides flight numbers of all ATSAW
symbols on ND (refer to extended label in Figure 3-12). The FLT ID ON/OFF
function is not available when the TRAF ON/OFF function is set to OFF.
The FLT ID ON/OFF function affects the own side ND only.
3.6.5.1.3.
TRAFFIC SELECT/DESELECT
The TRAFFIC SELECT/DESELECT function in the TRAFFIC INFORMATION page
selects or deselects the given aircraft. The selection/de-selection is accordingly
updated on ND. The TRAFFIC SELECT/DESELECT function is coordinated with the
Traffic Selector (refer to 3.6.5.2 – Traffic Selector).
Note: In any TRAF page, the flight number follows the same legend when the
flight crew:
• Highlights (flight number in cyan brackets on MCDU), or
• Selects (flight number in cyan on MCDU) the aircraft on ND.
Refer to Figure 3-13, Figure 3-19, Figure 3-21, and Figure 3-23.
- 3-38 -
Getting to grips with Surveillance
3.6.5.2.
3 – Traffic surveillance
TRAFFIC SELECTOR
Figure 3-30: Traffic Selector in the cockpit
The flight crew uses the Traffic Selector to highlight or select an ADS-B symbol on
ND. There is one Traffic Selector on either side of the cockpit for each flight crew
member.
3.6.5.2.1.
Turn to highlight
The flight crew turns the Traffic Selector to highlight an ATSAW symbol on ND.
The TCAS computer highlights aircraft as in Figure 3-13. A flight crewmember can
highlight only one aircraft at a time on his ND. A quick turn of the Traffic
Selector removes the highlight.
Turn
clockwise
to
highlight aircraft on ND
from the closest to the
farthest.
Turn counterclockwise
highlight aircraft on ND
from the farthest to the
closest.
Figure 3-31: Turn Traffic Selector to highlight
- 3-39 -
3 – Traffic surveillance
Getting to grips with Surveillance
3.6.5.2.2.
Pull to select
The flight crew pulls the Traffic Selector to select an ATSAW symbol on ND. Refer
to Figure 3-32. The flight crew can select only one aircraft at a time on ND. The
selection is shared on both NDs. The flight crew pushes the Traffic Selector to
deselect an ATSAW symbol.
Figure 3-32: Pull Traffic Selector to select
3.7.
OPERATIONAL RECOMMENDATIONS FOR ATSAW
3.7.1.
FOR THE AIRLINE
• Train your flight crews to use the ATSAW function in conjunction with
ATSAW applications (ATSA AIRB, ITP, VSA).
• Pay particular attention to the flight crew training related to ATSA ITP.
The flight crew must be aware of ATSA ITP basics (terminology, phraseology,
ITP criteria, normal and contingency procedures, etc).
3.7.2.
FOR THE FLIGHT CREW
• Do NOT use the ATSAW function for self-separation and collision
avoidance. The ATSAW function is an awareness tool that assists the flight
crew for the visual acuiqistion of surrounding aircraft capable of ADS-B OUT.
• Apply the TCAS procedures when a TA or RA occurs. Responsibilities do
not change. ATC remains responsible for aircraft separations.
• Always correlate ATSAW information with visual information out of the
window. Do not maneuver with information from the ATSAW function only.
3.8.
REGULATIONS FOR ATSAW
The interpretation of regulations in this paragraph is limited to AIRBUS aircraft at
the time of writing this brochure.
At the time of writing the present brochure, there is no mandate for the carriage
of the ATSAW function.
3.9.
MANUFACTURER FOR ATSAW
To fulfill the Traffic Awareness function with ATSAW, AIRBUS proposes the
following two systems: the Honeywell TPA 100B (available from early 2010) and
the ACSS T3CAS (available from early 2010). These TCAS computer capable of
ATSAW are also compliant with TCAS II Change 7.1 (refer to 3.1.6 – TCAS II
Change 7.1).
ATSAW ITP is an option of ATSAW.
- 3-40 -
Getting to grips with Surveillance
3 – Traffic surveillance
TCAS
TCAS
Antenna
Antenna
Radio
Radio
Altimeter
Altimeter
ADIRU
TCAS with
ATSAW
FWS
Mode
ModeSS
Transponder
Transponder
MMR
MMR
TrafficRMP
Selector
MCDU
HFDR
ND
HFDR
ATC/TCAS
Control Panel
Figure 3-33: ATSAW architecture
Figure 3-33 provides a simplified view of the ATSAW architecture.
3.10. FUTURE APPLICATIONS
3.10.1.
ATSA SURF WITH OANS
AIRBUS is currently developing the integration of the ATSA SURF application in
the OANS (refer to 5.1 – Description of OANS) for all AIRBUS aircraft. The ATSA
SURF application will provide the traffic around the aircraft on the OANS moving
map. The ATSA SURF application will improve taxi operations (e.g. anticipation of
aircraft queue for take-off) and safety on ground (i.e. traffic awareness during taxi
with low visibility).
3.10.2.
ENHANCED SEQUENCING AND MERGING OPERATIONS
AIRBUS actively participates to the development of new systems to assist the
flight crew in Sequencing and Merging (S&M) operations. Those systems (Airborne
Separation Assistance System – ASAS) will be able to merge the own aircraft
behind a preceding aircraft and to maintain a separation behind this aircraft. On
ATC instruction, the flight crew initiates the S&M procedure with the assistance of
ASAS.
The objectives of ASAS are to:
- Enable flight crews to precisely meet ATC spacing instructions
- Reduce ATC workload
- Improve current safety level
- Increase airspace capacity.
- 3-41 -
3 – Traffic surveillance
Getting to grips with Surveillance
Please bear in mind…
Description
The ATSAW function uses ADS-B data to enhance the Traffic Surveillance of
the flight crew. A new generation of TCAS computers hosts the ATSAW function.
The introduction of the ATSAW function in the TCAS computer does not change
the ACAS logic and the TCAS procedures. The ACAS and ATSAW software are fully
segregated inside the TCAS computer.
ATSAW applications are: ATSA AIRB, ATSA VSA, ATSA ITP, ATSA SURF (not
yet available).
TCAS computer capable of ATSAW on AIRBUS aircraft are: new version of
Honeywell TPA 100B (early 2010) and ACSS T3CAS (early 2010).
Operational recommendations
The main recommendations (but non exhaustive) are:
• An appropriate training on ATSAW with different applications (AIRB, ITP,
VSA)
• A particular attention to flight crew training to ATSA ITP
• The correlation of ATSAW information with visual information out of the
window
• The use of the ATSAW function for traffic awareness only.
Refer to 3.7 – Operational Recommendations for ATSAW.
Regulations
At the time of writing the present brochure, no country has required the carriage
of ATSAW.
Future systems
To improve the Traffic Surveillance during taxi, AIRBUS is currently developing the
integration of the ATSA SURF application in the OANS for all AIRBUS aircraft.
- 3-42 -
Getting to grips with Surveillance
4 – Terrain surveillance
4. TERRAIN SURVEILLANCE
4.1
4.1.1
4.1.1.1
4.1.1.2
4.1.1.3
4.1.1.4
4.1.2
4.1.2.1
4.1.3
4.1.3.1
4.1.3.2
4.1.3.3
4.1.4
4.1.4.1
4.1.4.2
4.1.5
4.1.5.1
4.1.5.2
4.1.5.3
4.1.5.4
4.1.5.5
4.1.6
4.1.6.1
4.1.6.2
4.2
4.2.1
4.2.2
4.3
4.4
4.4.1
4.4.2
4.5
Description of TAWS
TAWS Principles
Terrain Database
Obstacle Database
Runway Database
Aircraft Performance Database
Reactive (basic) TAWS Functions
EGPWS Mode 6: Excessive Bank Angle
Predictive TAWS Functions
Enhanced GPWS Functions
Predictive T2CAS Functions
EGPWS/T2CAS Comparison
Introduction of GPS Position into TAWS Architecture
EGPWS Geometric Altitude
Use of GPS for Lateral Positioning
TAWS Indications
TAWS Basic Mode Indications
TAWS Predictive Functions
EGPWS: Obstacle
EGPWS: Peaks Mode
Terrain Display in Polar Areas
TAWS Controls
A300/A310 Controls
A320/A330/A340 Controls
Operational Recommendations for TAWS
For the Airline
For the Flight Crew
Regulations for TAWS
Manufacturers for TAWS
Honeywell EGPWS
ACSS T2CAS
Future Systems
- 4-1 -
4-2
4-2
4-3
4-4
4-4
4-4
4-5
4-7
4-7
4-8
4-10
4-14
4-15
4-16
4-16
4-18
4-18
4-18
4-20
4-20
4-21
4-22
4-22
4-22
4-23
4-23
4-24
4-24
4-25
4-25
4-25
4-26
4 – Terrain surveillance
Getting to grips with Surveillance
The generic name of the system that fulfills the Terrain Awareness function is
Terrain Awareness and Warning System (TAWS). The TAWS alerts the flight
crew in a timely manner of hazardous situation ahead of the aircraft to avoid
Controlled Flight Into Terrain (CFIT). Honeywell was the first to propose the
Ground Proximity Warning System (GPWS), followed by the Enhanced
GPWS (EGPWS). Later on, ACSS released an integrated solution combining the
Traffic Awareness and the Terrain Awareness functions: the Traffic and Terrain
Collision Avoidance System (T2CAS). The TCAS part of T2CAS is identical to
the stand-alone TCAS 2000. The TAWS part of T2CAS is also called Ground
Collision Avoidance System (GCAS).
The present chapter describes the Terrain Awareness function as per (E)GPWS or
T2CAS. These two systems are quite similar. The differences are highlighted when
needed.
4.1.
DESCRIPTION OF TAWS
The TAWS functions may be split into three categories:
1. Basic TAWS functions for reactive modes 1 to 5 (a mode 6 is available on
A300/A310 aircraft only, refer to 4.1.2.1 – EGPWS Mode 6: Excessive Bank
Angle)
2. Enhanced TAWS functions for predictive functions (e.g. forward looking
capability)
3. Optional functions (e.g. peaks mode, obstacle detection, RAAS function on
EGPWS).
The following sections describe the TAWS functions regardless of the product
designations (EGPWS or T2CAS). Operational differences are highlighted when
necessary.
Note 1: In this brochure, EGPWS refers to P/N 965-1676-002 and T2CAS refers
to T2CAS standard 2.
Note 2: For the description of the EGPWS RAAS function, refer to 5.11 –
Description of RAAS.
4.1.1.
TAWS PRINCIPLES
The TAWS processing may be depicted as in Figure 4-1. The TAWS captures the
aircraft parameters from various sensors and systems. Based on its databases
and algorithms, the TAWS evaluates the aircraft situation regarding the
surrounding terrain, and triggers alerts and indications in the cockpit when a risk
of CFIT is identified. Based on the same database, the TAWS also displays the
terrain on ND for the awareness of flight crew.
The distance to the terrain/obstacle is determined according to the topography
recorded in the terrain/obstacle database (plains, hills, mountains). In addition,
the terrain displayed on ND is made up from the terrain database.
- 4-2 -
Getting to grips with Surveillance
4 – Terrain surveillance
Input Processing
Aircraft
Parameters
-
Databases
Terrains and Obstacles
Runways
Aircraft Performances
-
TAWS Algorithms
Reactive
Predictive
Output Processing
An outdated terrain/obstacle database may lead the TAWS to incorrectly evaluate
the CFIT risk or to trigger nuisance alerts. Therefore, it is recommended to always
get the latest terrain/obstacle database in the TAWS.
Alerts and
Displays
Figure 4-1: TAWS processing
Note: The Obstacle database is specific to EGPWS only. The Aircraft Performance
database is specific to T2CAS only.
4.1.1.1.
TERRAIN DATABASE
The terrain database has a worldwide coverage and is defined according to a
standardized Earth model: the World Geodetic System revised in 1984
(WGS84). The WGS84 defines the characteristics of the reference ellipsoid (semimajor axis, semi-minor axis, prime meridian, equator, etc). Based on this model,
the Earth surface is divided into grid sets. For each element of the grid sets, the
highest altitude above MSL is recorded and defines the terrain altitude in this
element.
In order to optimize the database size, the grid set resolution varies according to
the flight areas:
EGPWS
-
T2CAS
5 NM x 5 NM
2 NM x 2 NM
1 NM x 1 NM
0.5 NM x 0.5 NM
0.25 NM x 0.25 NM (airport vicinity).
- In en-route areas: 3.0 NM
- In terminal areas within 22 NM
from the airport: 0.5 NM
- In final areas for mountainous
airport (within 6 NM from airport if
elevation is 2 000 ft or more): 0.25 NM.
- 4-3 -
4 – Terrain surveillance
Getting to grips with Surveillance
Grid set resolution
Terrain
element
height
Grid set resolution
Figure 4-2: Terrain database encoding
4.1.1.2.
OBSTACLE DATABASE
At the time of writing the brochure, only EGPWS contains an Obstacle database,
which includes artificial obstacles worldwide. Thanks to this database, EGPWS
displays obstacles on ND.
4.1.1.3.
RUNWAY DATABASE
The TAWS also include a runway database. Functions that use the runway
database are:
- EGPWS Terrain Clearance Floor (TCF)
- EGPWS Runway Field Clearance Floor (RFCF)
- EGPWS Runway Awareness and Advisory System (RAAS)
- T2CAS Collision Prediction and Alerting (CPA)
- T2CAS Premature Descent Alert (PDA).
It includes runways longer than 3 500 ft (1 067 m) worldwide and runways longer
than 2 000 ft (610 m) locally.
4.1.1.4.
AIRCRAFT PERFORMANCE DATABASE
The T2CAS includes an Aircraft Performance database. The T2CAS Collision
Prediction and Alerting (CPA) function takes into account the aircraft
performances for the computation of escape maneuvers. The Aircraft Performance
database provides conservative climb rates taking into account aircraft weight,
altitude, SAT, landing gear and flap/slat configuration, engine out conditions.
- 4-4 -
Getting to grips with Surveillance
4 – Terrain surveillance
4.1.2.
REACTIVE (BASIC) TAWS FUNCTIONS
The following table summarizes the different reactive TAWS functions. The
penetration of a warning area triggers the call-out written inside. The charts are
illustrative. The figures on the coordinate axis may slightly differ from a
TAWS model to another (EGPWS or T2CAS). However, principles remain the
same. For more details, refer to your FCOM.
Mode 1 – Excessive Descent Rate
Mode 2A – Excessive Terrain Closure
Rate
Flaps not in landing configuration
Mode 2B – Excessive Terrain Closure
Rate
Flaps in landing configuration
Mode 3 – Excessive Altitude Loss
after Take-off
- 4-5 -
4 – Terrain surveillance
Getting to grips with Surveillance
Mode 4A – Unsafe Terrain Clearance
Gear up and flaps not in landing
configuration
Mode 4B – Unsafe Terrain Clearance
Gear down and flaps not in landing
configuration
Mode 4C – Unsafe Terrain Clearance
(EGPWS only)
Gear up or flaps not in landing
configuration
Mode 5 – Excessive Glide Slope
Deviation
A318: TAWS with Steep Approach
At the time of writing the brochure, only A318 aircaft is certified for steep
approaches. To avoid nuisance alerts during steep approaches, the TAWS Mode 1
envelope is slightly modified.
- 4-6 -
Getting to grips with Surveillance
4 – Terrain surveillance
Note: T2CAS Mode 2 is inhibited to avoid inadvertent alerts during approaches.
When there is a lateral position error, T2CAS reactivates Mode 2. For the same
purposes, EGPWS applies an envelope modulation (refer to 4.1.2.1.1 – EGPWS
Envelope Modulation).
4.1.2.1.
EGPWS MODE 6: EXCESSIVE BANK ANGLE
The EGPWS mode 6 is an option only
available
on
A300/A310
family
aircraft. It triggers a BANK ANGLE BANK
ANGLE aural alert when entering the
alert area and each time the roll angle
increases by 20%.
4.1.2.1.1.
EGPWS Envelope Modulation
The Envelope Modulation function adapts the caution and warning envelopes
according to the aircraft lateral position (GPS or FMS). The objective is to avoid
inadvertent cautions and warnings during approaches to some airports (e.g. rising
terrain just before the runway threshold, airport altitude significantly higher than
the surrounding terrain altitude).
The EGPWS crosschecks the FMS position with navaids data, altimeter and
heading data, and stored terrain data to guard against navigation errors. When
the FMS position crosscheck is positive, the Envelope Modulation function uses the
aircraft lateral position and the geometric altitude (refer to 4.1.4.1 – EGPWS
Geometric Altitude) to reduce the caution and warning envelopes during the
approach on specific areas.
4.1.3.
PREDICTIVE TAWS FUNCTIONS
EGPWS or T2CAS only (not GPWS) includes predictive TAWS functions (also
known as the enhanced functions for EGPWS). EGPWS and T2CAS provide
different methods for the prediction of collision. The following paragraphs describe
their respective predictive functions. A synthetic table provides at the end of this
section the equivalence between these different predictive functions.
- 4-7 -
4 – Terrain surveillance
4.1.3.1.
4.1.3.1.1.
Getting to grips with Surveillance
ENHANCED GPWS FUNCTIONS
EGPWS Terrain Awareness and Display (TAD)
The TAD function analyses the
terrain in caution and warning
envelopes (see Figure 4-3)
ahead and below the aircraft.
When a terrain penetrates one
of these envelopes, the TAD
function triggers visual and
aural alerts.
The envelopes are defined by:
- A centerline that lines up
with the ground track. A lead Figure 4-3: EGPWS terrain caution and warning
angle is added during turns.
envelopes
- A width that starts at ¼ NM (460 m) and gets wider ahead of the aircraft with
an aperture of 3 degrees on either side of the centerline.
- An altitude floor that is computed according to the aircraft altitude, the
nearest runway altitude, and the range to the nearest runway threshold. It
prevents irrelevant alerts at take-off and landing.
- A slope that varies with the aircraft Flight Path Angle (FPA).
- A look-ahead distance that is computed from the aircraft ground speed and
turn rate. It provides an advance alert with adequate time for the flight crew to
safely react. The caution look-ahead distance provides 40 to 60 seconds of
advance alerting. The warning look-ahead distance is a fraction of the caution
look-ahead distance.
The TAWS displays the
surrounding terrain on ND
according to the aircraft
altitude. A color-coding is
applied as in Figure 4-4.
The Reference Altitude is
projected down along the
flight path from the actual
aircraft altitude to provide a
30 second advance display
when
the
aircraft
is
descending more than 1 000
ft/min.
The EGPWS provides two
different modes of terrain
Figure 4-4: EGPWS color coding with peaks option
display on ND:
- Standard mode: the terrain is displayed according to the vertical
displacement between the terrain elevation and the current aircraft altitude (left
- 4-8 -
Getting to grips with Surveillance
OPS+
4 – Terrain surveillance
side of Figure 4-4). If the aircraft is more than 2 000 ft above the terrain, there is
no terrain information displayed.
- Peaks mode (refer to 4.1.5.4 – EGPWS: Peaks Mode): it displays terrain
regarding to the absolute terrain elevation (i.e. referring to the sea level instead
of the aircraft elevation). It improves the terrain awareness of the flight crew
(right side of Figure 4-4). Practically, if the aircraft is more than 2 000 ft above
the terrain, the terrain is still displayed with a gradient of green colors. In
addition, the Peaks mode provides two figures in the bottom right corner of the
display, which are the highest and lowest terrain elevations. The lowest terrain
elevation refers to the lowest terrain information contained in the terrain
database.
Tips: EGPWS Peaks mode and RNP AR
The EGPWS Peaks mode has been identified as mandatory during the RNP AR
certification process. For the time being, only the EGPWS Peaks mode feature is
eligible for RNP AR operations.
The future T3CAS will encompass an equivalent feature called Eleview (see 4.1.3.3
– EGPWS/T2CAS Comparison).
4.1.3.1.2.
EGPWS Terrain Clearance Floor (TCF)
The TCF function provides an additional terrain clearance envelope around the
runway against situations where Mode 4 provides limited or no protection. When
the aircraft penetrates the terrain clearance envelope, the EGPWS triggers aural
and visual alerts.
TCF alerts take into account
the current aircraft location,
the reference point of the
destination runway, and the
radio altitude.
The
terrain
clearance
envelope is defined as in
Figure 4-5.
Figure 4-5: TCF envelope
4.1.3.1.3.
EGPWS Runway Field Clearance Floor (RFCF)
The RFCF function complements the TCF function. It provides a circular envelope
centered on the selected runway, extending up to 5 NM from the runway end. The
inner limit of the RFCF envelope is set at K NM (K depends of the position error,
the runway data quality and geometric altitude quality).
- 4-9 -
4 – Terrain surveillance
Getting to grips with Surveillance
The RFCF function provides alerts
for cases where the runway is at
high elevation compared to the
terrain below the approach path.
In these cases, the radio altitude
may be so high that the EGPWS
does not trigger TCF alerts,
whereas the aircraft could be
below the runway elevation.
The field clearance is defined as
the current aircraft altitude (MSL)
minus the elevation of the
selected runway.
4.1.3.2.
Figure 4-6: RFCF envelope
PREDICTIVE T2CAS FUNCTIONS
T2CAS Collision Prediction and Alerting (CPA)
4.1.3.2.1.
The CPA function provides the flight crew with alerts indicating that the current
flight path is hazardous due to the presence of terrain ahead. The alerts permit a
timely initiation of the suitable escape maneuver to avoid a CFIT. A pull up is
considered as the basic escape maneuver (PULL UP warning). When the pull up is
not possible, the T2CAS announces a turn around maneuver (AVOID TERRAIN
warning).
For the prediction of CFIT, the CPA detects the terrain profile (augmented by an
additional margin above the terrain element height, called Minimum Terrain
Clearance Distance – MTCD) with a clearance sensor. Refer to Figure 4-8.
The terrain profile is
extracted from the terrain
database.
The
MTCD
depends on the distance to
the nearest airport, the
height
to
the
airport
elevation, and the aircraft
vertical speed. The MTCD is
composed of a basic term
and an offset term.
Figure 4-7: Variation of the basic MTCD
The variation of the basic MTCD is given in Figure 4-7. The offset MTCD varies
according to the distance to the airport, and the vertical speed. The shape of the
clearance sensor depends on the FPA and the aircraft performances.
- 4-10 -
Getting to grips with Surveillance
4 – Terrain surveillance
112 s
112 s
8s
Terrain
element
height
20 s
Warning Sensor
Caution Sensor
MTCD
Figure 4-8: T2CAS terrain caution and warning envelopes
Three segments compose the clearance sensors (see Figure 4-8):
1. A projection of the current flight path (8 seconds for the warning
sensor, 20 seconds for the caution sensor)
2. A vertical maneuver at constant 1.5 G maneuver
3. A projection of the aircraft climb as per Aircraft Performance
database.
In mountainous approach areas, the sensors are linearly reduced to about 30
seconds to avoid undue alerts at low altitude.
If the sensor interferes the MTCD for at least 2 seconds, the T2CAS triggers an
aural alert (TERRAIN AHEAD caution or warning). In case of a late reaction from
the flight crew or in case of very steep terrain environments, the vertical pull up
maneuver may not clear the CFIT risk. In these cases, the T2CAS orders a lateral
maneuver (AVOID TERRAIN warning).
Terrain AHEAD caution, TERRAIN AHEAD – PULL UP warning, AVOID
TERRAIN warning
The AVOID TERRAIN warning is computed thanks to the Aircraft Performance
database and is available on T2CAS only. When T2CAS triggers the AVOID
TERRAIN warning, the flight crew should consider a lateral avoidance (turn). Refer
to your FCOM for the applicable procedure.
- 4-11 -
4 – Terrain surveillance
Getting to grips with Surveillance
On the horizontal plane (see Figure 4-9),
the sensor opens up by 1.5° on either side
of the track. The aperture of the sensor
goes up to 90° during turns. The sensor
width starts at 100 m (if GPS error < 100
m) or 200 m (if GPS error > 100m).
To avoid undue CPA alerts when the
aircraft is close to the runway, CPA alerts
are inhibited in normal take-off
conditions or when the aircraft is
safely
converging
towards
the
runway.
Figure 4-9: T2CAS horizontal sensor
coverage
The take-off is considered as normal if:
- The vertical speed is not negative for more than 2 seconds
- The distance to the runway threshold is less than 1.9 NM
- Various criteria relative to the variations of MSL altitude, track angle and Radio
Altitude are met.
The Runway Convergence
protection provides alerts
when the aircraft performs a
premature descent or flies an
unsafe approach flight path.
The
runway
convergence
protection is available until
the aircraft is within 90 ft
above the runway.
The T2CAS considers the
runway convergence as safe
when:
- Landing gears are down
and flaps/slats in landing
Figure 4-10: Runway convergence envelope
configuration
- The distance to the runway threshold is less than 5 Km (2.7 NM)
- The aircraft remains in the runway convergence envelope
- The aircraft track remains in an inhibition range
- If RA is not valid, the vertical speed is in an inhibition range.
- 4-12 -
Getting to grips with Surveillance
4 – Terrain surveillance
If the runway threshold coordinates are not in runway database, the CPA function
is deactivated if the aircraft is within 1.9 NM from the airport reference point
(horizontal distance) and within 900 ft from the elevation of the airport reference
point (vertical distance). The green TERR STBY memo is displayed on ECAM and
Mode 2 is permanently activated.
4.1.3.2.2.
T2CAS Terrain Hazard Display (THD)
The T2CAS provides only the
Standard mode display (compared
to EGPWS, see Figure 4-4). In
descent, the T2CAS provides an
anticipated
terrain
situational
awareness. The Reference Altitude
is defined as the aircraft altitude
projected 30 seconds along FPA
(refer to Figure 4-11).
Figure 4-11: T2CAS color coding
T2CAS Premature Descent Alert (PDA)
4.1.3.2.3.
The PDA function provides
Clearance sensor
alerts when the aircraft is
Escape maneuver
Level off altitude
descending and the terrain of
concern is below instead of MTCD
ahead of the aircraft. The PDA
is an alternative to the CPA
TERRAIN
AHEAD
caution
each time a level off
maneuver, rather than a
climb one, is sufficient to
clear the collision risk. The
PDA function triggers an aural
Figure 4-12: Level off with Premature Descent
alert
only
(TOO
LOW
Alert
TERRAIN). No indication is
displayed on ND.
The T2CAS triggers the Premature Descent Alert when:
- The Caution clearance sensor interferes with the MTCD for more than 2
seconds
- No TERRAIN AHEAD caution had been triggered
- The vertical speed is negative
- The level off altitude is above the MTCD
- The radio altitude is invalid or below a given threshold (1 000 ft in en-route
phase, 750 ft in terminal phase, 500 ft in final phase).
- 4-13 -
4 – Terrain surveillance
4.1.3.3.
Getting to grips with Surveillance
EGPWS/T2CAS COMPARISON
EGPWS
T2CAS
Reactive modes:
Imminent Contact Alerting
Mandatory functions
Modes 1 to 5 (GPWS)
Modes 1 to 5
Locally desensitized using envelope Mode 2 inhibited when altitude check
modulation
correct
Predictive modes:
Forward Looking Terrain Alerting
Terrain Alerting and Display (TAD) Collision Prediction and Alerting
based on Terrain database
(CPA) based on Terrain and Aircraft
Performance databases
« Terrain Ahead »
« Terrain Ahead »
« Terrain Ahead Pull Up »
« Terrain Ahead Pull Up »
« Avoid Terrain »
Premature Descent Alerting
« Too Low Terrain »
Terrain Display
Terrain Alerting and Display (TAD) Terrain Hazard Display (THD) based
based on Terrain database
on Terrain database
Voice call outs
Managed by FWS (500ft or 400ft call out)
Automatic Deactivation of FMS Source
FAA audio
Caution Terrain instead of Terrain Ahead
Terrain Terrain Pull up instead of Terrain Ahead Pull Up
Other functions
Bank Angle alerting (A300/310 aircraft only)
Geometric Altitude
(Hybrid
or
Autonomous
Architecture)
Radio Altitude Blending + GPS
GPS altitude activation
(Hybrid
or
Autonomous
GPS
Architecture)
GPS Lateral Position
(Hybrid or Autonomous GPS Architecture)
Obstacle database
Peaks mode
Compatible with Honeywell Autotilt Not compatible with
weather radar
Autotilt weather radar
FLS support (mode 5)
Runway Awareness and Advisory
System (RAAS)
- 4-14 -
Honeywell
Getting to grips with Surveillance
4 – Terrain surveillance
Note: Functions shaded in yellow are basically activated in forwardfit.
4.1.4.
OPS+
INTRODUCTION OF GPS POSITION INTO TAWS ARCHITECTURE
The improvement of TAWS functions
relies on the use of the vertical and
lateral GPS positions. The use of vertical
and lateral GPS positions gets rid of
drifts from barometric altitude and FMS
position. Such drifts are known to cause
spurious alerts (e.g. over-flown aircraft,
map shift) and unnecessary go-arounds.
ADIRU 1
ADR data
IR data
Navaids
IR data
FMS Capt
The use of vertical and lateral GPS
positions introduces slight modifications
in the avionics architecture. According to
the aircraft configuration, the new
avionics architecture is called:
FM position
TAWS
Computer
ALERTS
Figure 4-13: Former TAWS architecture
- Hybrid architecture for aircraft
equipped with ADIRU 4MCU able to
process GPS position. TAWS uses the
pure GPS position from MMR or GPS-SU
via ADIRU. It is the most commonly
used (A320/A330/A340).
- Autonomous
architecture
for
aircraft equipped with ADIRU 10MCU not
able to process GPS position. TAWS uses
the GPS position directly from MMR or
GPS-SU. It applies on former AIRBUS
aircraft (A300/A310 and former A320).
MMRs or GPS-SU
ADIRU 1
GPS
+
ADR data
IR data
MMRs
or GPS-SU
Navaids
ADIRU 1
GPS
+
IR data
ADR data
IR data
Navaids
GPS
IR data
FMS Capt
FMS Capt
FM position
(Back-up)
FM position
(Back-up)
TAWS
Computer
ALERTS
Figure 4-14: Hybrid architecture
TAWS
Computer
ALERTS
Figure 4-15: Autonomous architecture
- 4-15 -
4 – Terrain surveillance
Getting to grips with Surveillance
Both new EGPWS (P/N 965-1676-002 and subsequent) and T2CAS (Standards 1 &
2) include the provisions for the use of the vertical and lateral GPS positions. The
use of the vertical and lateral GPS positions is not mandatory and remains an
optional feature on both new EGPWS and T2CAS. Besides, the installation of new
EGPWS or T2CAS does not ensure that the aircraft is protected against spurious
alerts. AIRBUS strongly recommends implementing the GPS position into
the TAWS architecture, especially when MMRs or GPS-SU are already installed.
Refer to AIRBUS References for OITs on this topic.
4.1.4.1.
EGPWS GEOMETRIC ALTITUDE – T2CAS CPA ALTITUDE
When operating with extreme local temperature variations, in non-standard
altitude conditions (i.e. QNH or QFE), or when the altimeter is not set
correctly, the barometric altitude may significantly deviate from the current
altitude.
To provide efficient alerts with appropriate altitude clearances regardless of
temperature/pressure variations, QNH/QFE or manual error settings, new
generation TAWS use the Geometric Altitude (also known as Alternate
Vertical Position based on GPS for T2CAS). The Geometric Altitude takes into
account the GPS altitude, an improved barometric altitude calculation, the radio
altitude, and the terrain/runway elevations. The Geometric Altitude provides a
more reliable altitude indication to TAWS. Indeed, temperature/pressure
variations, altimeter settings (QNH/QFE or manual) do not affect the GPS
altitude.
4.1.4.2.
USE OF GPS FOR LATERAL POSITIONING
In-service experience has shown that improper IR alignments or erroneous navaid
signals may affect FM and ADIRU data. Consequently, the TAWS position (FM
position or IR data) may significantly deviate from the current aircraft position.
This deviation from the current aircraft position is known as Map Shift.
Note : The SIL 22-043 describes the root causes of a Map Shift (See AIRBUS
References) and proposes some solutions. The following summarizes the
root causes:
On ground:
o Incorrect PPOS at IR initialization,
o Take-off update: incorrect FM position at take-off power setting,
o ADIRU auto-calibration malfunction.
In flight:
o Incorrect Navaids coordinates in FM NAV database,
o Excessive IR drift.
During approach:
o LOC update: incorrect LOC data in FM NAV database,
o Incorrect information provided by Navaids.
The TAWS displays the terrain background on ND according to its terrain database
and the FM position (with former TAWS architecture). The deviation of the FM
position from the current aircraft position induces a shift of the terrain display on
- 4-16 -
Getting to grips with Surveillance
4 – Terrain surveillance
ND. The Map Shift may cause some spurious alerts or inhibit real alerts. Figure
4-16 illustrates a Map Shift that leads to spurious alerts.
The Use of GPS for Lateral Positioning (also known as Alternate Lateral
Position based on GPS for T2CAS) significantly reduces errors in the calculation
of the aircraft position. Consequently, it reduces occurrences of spurious errors.
In addition, the use of GPS for lateral positioning:
• Improves the TAWS performance thanks to a more accurate aircraft position
• Reduces the dependence between the navigation (i.e. FMS) and the
surveillance (i.e. TAWS).
Within the former TAWS architecture (refer to Figure 4-13), the position
source is:
1. The FM position first, then
2. IR data if the FM position is unavailable.
Within the hybrid (refer to Figure 4-14) or autonomous architecture (refer to
Figure 4-15), the selection of the position source applies the following sequence
(by order of priority):
1. GPS position, then
2. IR data (from ADIRU 1 on A320/A330/A340 aircraft or IRU 1 for A300/A310
aircraft) combined with the last valid GPS data (GPIRS), then
3. FM position (from FMGEC 1 for A320/A330/A340 aircraft or FMS 1 for
A300/A310 aircraft)
When all these sources are not valid or not accurate enough:
- If the automatic deactivation of predictive TAWS functions has been selected
(pin-programming), TAWS automatically deactivates predictive functions (basic
TAWS functions remain active).
- If the automatic deactivation of predictive TAWS functions has not been
selected, the flight crew must manually switch predictive functions to OFF (TERR
to OFF, refer to 4.1.6 – TAWS Controls).
Figure 4-16: Map Shift due to an FM position error
- 4-17 -
4 – Terrain surveillance
Getting to grips with Surveillance
4.1.5.
TAWS INDICATIONS
This section briefly describes indications and controls. For more details, please
refer to your FCOM.
4.1.5.1.
TAWS BASIC MODE INDICATIONS
Please refer to 4.1.2 for the aural alerts provided in TAWS basic modes.
For EGPWS or T2CAS:
When the TAWS triggers a caution, the When the TAWS triggers a warning, the
PULL UP light comes on.
GPWS light comes on.
4.1.5.2.
TAWS PREDICTIVE FUNCTIONS
The TAWS display on ND is available in ROSE and ARC modes.
TERRAIN AHEAD Caution
TERRAIN AHEAD Warning
TERRAIN AHEAD 1
- EGPWS: Every 7 seconds until
conditions disappear.
- T2CAS: When the caution sensor
penetrates the MTCD for at least 2
seconds.
Every
5
seconds
until
conditions disappear.
TERRAIN AHEAD – PULL UP 2
- EGPWS: Repeated until condition
disappears.
- T2CAS: When the warning sensor
penetrates the MTCD for at least 2
seconds. Repeated until conditions
disappear.
1
The European EASA regulations require the wording TERRAIN AHEAD. The FAA regulations require
CAUTION TERRAIN.
2
The European EASA regulations require the wording TERRAIN AHEAD – PULL UP. The FAA
regulations require TERRAIN TERRAIN – PULL UP.
- 4-18 -
Getting to grips with Surveillance
4 – Terrain surveillance
TOO LOW TERRAIN
- EGPWS TCF: When the aircraft penetrates the TCF envelope and
each time the AGL altitude deteriorates by 20%.
- T2CAS PDA: Refer to 4.1.3.2.3 – T2CAS Premature Descent Alert
(PDA) for triggering conditions.
AVOID TERRAIN Warning
AVOID TERRAIN 3 - T2CAS only when a pull up maneuver does not clear
the CFIT risk. The flight crew should
consider a turn (lateral avoidance) as
the
pull
up
maneuver
(vertical
avoidance) is not sufficient. Refer to
your FCOM for the applicable procedure.
On ND, black crosses are added in the
red area.
3
The TERRAIN AHEAD – PULL UP warning (or the equivalent FAA warning) always precedes the
AVOID TERRAIN warning.
- 4-19 -
4 – Terrain surveillance
4.1.5.3.
Getting to grips with Surveillance
EGPWS: OBSTACLE
The Obstacle option uses the same TAD algorithm for terrain detection. Only the
visual and aural alerts differ.
OBSTACLE AHEAD Caution
OBSTACLE AHEAD 4 every
seconds until conditions disappear.
OBSTACLE AHEAD Warning
7
OBSTACLE AHEAD – PULL UP 5
repeated until condition disappears.
The displays on ND are similar to the ones for TERRAIN caution and warning. The
term OBST replaces the term TERRAIN. The wording varies in the same way
according to the regulations (EASA or FAA). Refer to 4.1.5.2 – TAWS Predictive
Functions.
4.1.5.4.
OPS+
EGPWS: PEAKS MODE
The Peaks mode display is optional. It
improves the terrain awareness of the
flight crew by displaying the terrain data
further than 2 000 ft below the aircraft.
Refer to Figure 4-4.
The highest and the lowest terrain
altitudes are displayed in the ND bottom
right corner. The lowest terrain altitude
is available on EIS2 only. Refer to Figure
4-17.
Figure 4-17: EGPWS Peaks mode
4
The European EASA regulations require the wording OBSTACLE AHEAD. The FAA regulations
require CAUTION OBSTACLE.
5
The European EASA regulations require the wording OBSTACLE AHEAD – PULL UP. The FAA
regulations require OBSTACLE OBSTACLE – PULL UP.
- 4-20 -
Getting to grips with Surveillance
4.1.5.5.
4 – Terrain surveillance
TERRAIN DISPLAY IN POLAR AREAS
The terrain database is coded in latitudes/longitudes (spherical coordinates) and
the ND is graduated in NM (plane cylindrical coordinates). The TAWS translates
the latitudes/longitudes into distances (i.e. projection of a spherical image on a
plan). At high latitudes, discontinuities appear in the terrain display (refer to
Figure 7-10). Only EGPWS is affected.
OPS+
The T2CAS assigns a unique elevation to
the region that is above 75° of latitude
(North or South). This unique elevation is
the highest elevation of the region above
75° of latitude (North or South). Refer to
Figure 4-18.
In other words, the T2CAS considers this
region as a cylindrical mountain. The
Figure 4-18: Unique terrain elevation height of this cylindrical mountain is
beyond N75° or S75°
equal to the highest elevation in this
region.
Figure 4-19 provides the areas contained in the N75° and S75° circles.
Refer to 7.1.3.3 – Terrain Display in Polar Areas for more details.
Figure 4-19: Areas beyond N75° and S75°
- 4-21 -
4 – Terrain surveillance
4.1.6.
4.1.6.1.
Getting to grips with Surveillance
TAWS CONTROLS
A300/A310 CONTROLS
GPWS LANDING SLATS/FLAPS: TAWS activation of
the 15/20 slats/flaps configuration for A300-600 (or
20/20 for A310) if the landing is not performed in
30/40 slats/flaps configuration.
Figure 4-20: GPWS landing
SLATS/FLAPS switch
GPWS G/S MODE: Inhibition of Mode 5 – Excessive
Glide Slope Deviation.
TERR MODE: Inhibition of predictive functions
(TAD/TCF for EGPWS or CPA/THD for T2CAS).
GPWS: Inhibition of basic functions.
Figure 4-21: Control panel
on Captain side
GPWS Selector switch:
OFF: Inhibition of all warnings.
FLAP OVRD: Inhibition of TOO LOW FLAPS alert.
NORM: All GPWS warnings available.
TERR ON ND: Display of TAWS terrain information on
ND.
Figure 4-22: TERR ON ND
pushbutton
4.1.6.2.
A320/A330/A340 CONTROLS
Figure 4-23: A320 overhead panel
Figure 4-24: A330/A340 overhead panel
- 4-22 -
TERR:
Inhibition
of
predictive
functions (TAD/TCF for EGPWS or
CPA/THD for T2CAS).
SYS: Inhibition of basic functions.
G/S MODE: Inhibition of Mode 5 –
Excessive Glide Slope Deviation.
FLAP MODE: Inhibition of TOO LOW
FLAPS alert.
LDG FLAP 3: Inhibition of TOO LOW
FLAPS alert when landing in CONF 3
(A320 family aircraft only).
Getting to grips with Surveillance
4 – Terrain surveillance
Tips: Set TERR to OFF when navigation accuracy check is negative
When GPS PRIMARY is lost (or GPS is not installed) and when the FMS navigation
accuracy check negative, the estimated aircraft position is not reliable enough for
the terrain awareness. A map shift (refer to Figure 4-16) may occur and false alerts
may be triggered.
Figure 4-25: TERR ON ND pushbutton
4.2.
TERR ON ND: Display of TAWS
terrain information on ND.
Note 1: TAWS terrain information
and WXR weather information cannot
be simultaneously displayed on ND.
Note 2: The TAWS automatically
displays terrain information on ND if
the TAWS triggers a predictive alert.
OPERATIONAL RECOMMENDATIONS FOR TAWS
This paragraph of operational recommendations is intentionally non-exhaustive. For
more recommendations, please check your FCOM and/or FCTM as they are more
frequently updated.
4.2.1.
FOR THE AIRLINE
• Operate your aircraft with the latest terrain database provided by the
TAWS manufacturer. Refer to SIL 34-080 (See AIRBUS References) for more
information on terrain database update. Terrain database can be downloaded
at:
EGPWS: http://www.honeywell.com/sites/aero/Egpws-Home.htm.
T2CAS: http://www.acsscustomerservices.com/CustomerServices/.
Note:
•
•
States that are ICAO members provide the TAWS manufacturers with
the terrain database contents. Each State is responsible for the
definition of the terrain database content. The operator is responsible
for verifying the correctness of the terrain database contents with the
appropriate State in which the operator operates. The operator shall
report errors in the terrain database to the appropriate State and its
TAWS manufacturer. AIRBUS SAS does not accept any liability
for the contents, acquisition, use or update of the terrain
database.
Report any repetitive difficulties with a given airport to AIRBUS via your
Customer Service Director (CSD).
Train your flight crews to use TAWS and to respond to TAWS alert safely
and efficiently.
- 4-23 -
4 – Terrain surveillance
Getting to grips with Surveillance
•
AIRBUS strongly recommends the implementation of the GPS position
into the TAWS architecture. Refer to 4.1.4 – Introduction of GPS Position
into TAWS Architecture and OIT 999.0015/04, 999.0050/06 or 999.0034/07
(See AIRBUS References).
•
Take cognizance of the Flight Safety Foundation (FSF) Approach-andLanding
Accident
Reduction
(ALAR)
tool
kit
(available
at
http://www.flightsafety.org/ecommerce/) and spread out its contents inside
the company as necessary.
4.2.2.
FOR THE FLIGHT CREW
• Stick to the procedures. Refer to your FCOM for the appropriate procedures.
Refer to FOBN “Operating Environment – Enhancing Terrain Awareness” (See
AIRBUS References) for a comprehensive set of recommendations.
• Know where you are, Know where you should be, and Know where the
terrain and obstacles are.
• Check the altimeter settings (reference – standard, QNH, QFE – and units –
hPa, inHg, meters, feet). Refer to FOBN “Supplementary Techniques – Use of
Radio Altimeter” (See AIRBUS References).
• Know how your TAWS operates.
• Respond to TAWS alerts without delay in an appropriate manner.
• Correlate the results of the navigation accuracy check with the
operation of the predictive TAWS functions (e.g. overhead TERR switched
to OFF when GPS PRIMARY is lost and NAV mode cannot be continued –
applicable only if the automatic TERR deselection has not been activated).
• Chase doubts in ATC communications, especially during approach and
landing (e.g. confirmation of radar contact, altimeter settings). Refer to FOBN
“Human Performance – Effective Pilot/Controller Communications” (See
AIRBUS References).
4.3.
REGULATIONS FOR TAWS
The interpretation of regulations in this paragraph is limited to AIRBUS aircraft at
the time of writing this brochure.
The carriage of TAWS with forward-looking terrain avoidance function (i.e.
predictive functions) is mandatory in all ICAO member States as per ICAO Annex
6 – Operation of Aircraft – Part I:
“6.15.2 All turbine-engined aeroplanes of a maximum certificated take-off mass in
excess of 15 000 kg or authorized to carry more than 30 passengers shall be
equipped with a ground proximity warning system which has a forward looking
terrain avoidance function.”
As per EASA EU OPS 1.665:
- TAWS with a predictive terrain hazard warning function is mandatory.
- 4-24 -
Getting to grips with Surveillance
4 – Terrain surveillance
As per FAA FAR 121.354:
- TAWS is mandatory for aircraft manufactured after 29 MAR 2002.
- TAWS is mandatory since 29 MAR 2005 for aircraft manufactured on or before
29 MAR 2002.
4.4.
MANUFACTURERS FOR TAWS
To fulfill the Terrain Awareness function, AIRBUS proposes the following two
systems: the Honeywell EGPWS and the ACSS T2CAS, available at the time of
writing the brochure.
FMS
RA
SFCC
GPS*
GPS
ILS
GPS
ADIRU
TAWS
FCU
WXR
TAWS
CP
RMP
ND
HFDR
Figure 4-26: TAWS architecture
Figure 4-26 provides a simplified view of the TAWS architecture.
* Refer to 4.1.4 – Introduction of GPS Position into TAWS Architecture for details.
4.4.1.
HONEYWELL EGPWS
The Honeywell GPWS was the first system to be certified on AIRBUS aircraft in
early 1990s. The Honeywell EGPWS was the first system capable of predictive
functions
to
be
certified
on
AIRBUS
aircraft
in
late
1990s
on
A300/A310/A320/A330/A340 aircraft.
More information is available at http://www.honeywell.com/sites/aero/EgpwsHome.htm.
4.4.2.
ACSS T2CAS
The ACSS T2CAS includes a TAWS module capable of predictive functions. It was
certified in 2004 on AIRBUS aircraft.
As the name indicates, the T2CAS encompasses two functions (traffic awareness
and terrain awareness) into the same Line Replaceable Unit (LRU). In terms of
- 4-25 -
4 – Terrain surveillance
Getting to grips with Surveillance
architecture, the T2CAS LRU is inserted into the ACAS LRU (e.g. TCAS 2000) and
EGPWS wirings are directly connected to the T2CAS (refer to Figure 4-28).
The advantages of T2CAS are less weight, simplified maintenance, less wiring,
less sparing.
More information is available at http://www.acssonboard.com/products/t2cas/.
TAWS wiring
provisions
ACAS wiring
provisions
TAWS wiring
provisions
ACAS wiring
provisions
T2CAS Wiring
provisions
EGPWS
TCAS
EGPWS
Figure 4-27: Standard architecture
TCAS
Figure 4-28: T2CAS architecture
4.4.3.
TAWS MODULE OF ACSS T3CAS
The ACSS T3CAS is a further step of integration including:
- A Mode S transponder capable of ADS-B OUT as per DO-260A Change 2
- A TCAS compliant with TCAS II Change 7.1
- An enhanced TAWS module derived from T2CAS TAWS module.
The advantages of this integration are the same as for T2CAS, a step further:
reduced weight, volume, wiring, and power consumption.
The TAWS module of T3CAS is developed from the TAWS module of T2CAS. It will
also include additional features such as:
- The Eleview (equivalent to the EGPWS Peaks mode) that enables RNP AR
operations
- The obstacle database.
The certification of the T3CAS is expected by end 2009. More information is
available at http://www.acssonboard.com/media/brochures/T3CAS.pdf.
4.5.
FUTURE SYSTEMS
At the time of writing the brochure, no new TAWS computer is expected on a
short term.
- 4-26 -
Getting to grips with Surveillance
4 – Terrain surveillance
Please bear in mind…
Description
The Terrain Surveillance function had been previously fulfilled with Ground
Proximity Warning System (GPWS) that includes the reactive/basic functions
(i.e. Mode 1 to 5).
Today, it is fulfilled by Terrain Awareness System (TAWS) with enhanced
functions also known as predictive functions in addition to basic functions. The
main TAWS products available on AIRBUS aircraft are:
• Honeywell EGPWS with its predictive functions: Terrain Awareness and
Display – TAD, Terrain Clearance Floor – TCF, and Runway Field Clearance
Floor (RFCF).
• ACSS T2CAS with its predictive functions: Collision Prediction and Alerting
– CPA and Terrain Hazard Display – THD.
• ACSS T3CAS that includes a transponder, a TCAS, and a TAWS module
with Eleview and an obstacle databse.
Refer to 4.1.3.3 – EGPWS/T2CAS Comparison to compare both products.
Operational recommendations
The main recommendations (but non exhaustive) are:
• A regular update of TAWS terrain database,
• The implementation of the GPS position into the TAWS architecture,
• The activation of predictive TAWS functions,
• An appropriate and recurrent training on TAWS,
• Good knowledge of TAWS operations and escape maneuvers.
Refer to 4.2 – Operational Recommendations for TAWS.
Regulations
The carriage of TAWS is mandatory as per ICAO Annex 6 – Operation of
Aircraft – Part I.
Future systems
At the time of writing the brochure, no new TAWS computer is expected on a
short term.
- 4-27 -
Getting to grips with Surveillance
5 – Runway surveillance
5. RUNWAY SURVEILLANCE
On-board Airport Navigation System – OANS
5.1
5.1.1
5.1.1.1
5.1.1.2
5.1.1.3
5.1.1.4
5.1.1.5
5.1.1.6
5.1.1.7
5.1.2
5.1.2.1
5.1.2.2
5.1.3
5.1.3.1
5.1.3.2
5.1.3.3
5.1.3.4
5.1.3.5
5.1.3.6
5.1.4
5.1.4.1
5.1.4.2
5.1.4.3
5.1.4.4
5.1.4.5
5.1.4.6
5.2
5.2.1
5.2.2
5.3
5.4
5.4.1
5.5
Description of OANS
OANS Terminology
Airport Mapping Data Base (AMDB)
Airport Data Base (ADB)
Airport Map
Coverage Volume
Airport Map Displayed in ARC and ROSE NAV Mode
Airport Map Displayed in PLAN Mode
Map Reference Point
OANS Principles
Airport Moving Map
Approaching Runway Advisory
OANS Indications
Aircraft Symbol
FMS Active Runway
FMS Destination Arrow
Airport Map
Approaching Runway Indication
OANS Messages
OANS Controls
EFIS CP Range Selector
EFIS CP ND Display Mode
KCCU
MOVE Function
Interactive Control Menu
Soft Control Panel
Operational Recommendations for OANS
For the Airline
For the Flight Crew
Regulations for OANS
Manufacturer for OANS
Update of OANS Databases
Future Systems
- 5-1 -
5-4
5-4
5-4
5-4
5-4
5-5
5-5
5-5
5-5
5-5
5-5
5-6
5-7
5-8
5-8
5-9
5-9
5-11
5-12
5-13
5-13
5-13
5-15
5-15
5-15
5-15
5-16
5-16
5-17
5-17
5-17
5-18
5-18
5 – Runway surveillance
Getting to grips with Surveillance
Runway end Overrun Warning and Protection – ROW/ROP
Brake To Vacate - BTV
5.6
5.6.1
5.6.1.1
5.6.1.2
5.6.1.3
5.6.1.4
5.6.1.5
5.6.2
5.6.3
5.6.3.1
5.6.3.2
5.6.3.3
5.6.3.4
5.6.4
5.7
5.7.1
5.7.2
5.8
5.9
5.10
Description of ROW/ROP
ROW/ROP Principles
Automatic Detection of the Runway for Landing
ROW Armed
ROW Engaged
ROP Armed
ROP Engaged
Auto Brake Disconnection
ROW/ROP Indications
ROW Indications When Armed
ROW Indications When Engaged
ROP Indications When Armed
ROP Indications When Engaged
Indications for Auto Brake Disconnection
Operational recommendations for ROW/ROP
For the airline
For the flight crew
Regulations for ROW/ROP
Manufacturers for ROW/ROP/BTV
Future systems
5-20
5-21
5-22
5-22
5-22
5-23
5-23
5-23
5-24
5-24
5-24
5-26
5-26
5-27
5-28
5-28
5-28
5-28
5-29
5-29
Runway Awareness and Advisory System – RAAS
5.11
5.11.1
5.11.1.1
5.11.1.2
5.11.2
5.11.2.1
5.11.2.2
5.11.3
5.11.3.1
5.11.3.2
5.12
5.13
5.14
5.15
Description of RAAS
Approaching Runway – On Ground Advisory
Routine
Purpose
Triggering Conditions
On Runway Advisory – Routine
Purpose
Triggering Conditions
Takeoff on Taxiway Advisory – Non-Routine
Purpose
Triggering Conditions
Operational Recommendations for RAAS
Regulations for RAAS
Manufacturer for RAAS
Future Systems
- 5-2 -
–
5-31
5-31
5-31
5-31
5-32
5-32
5-32
5-32
5-32
5-32
5-33
5-33
5-33
5-33
Getting to grips with Surveillance
5 – Runway surveillance
The unfortunately famous runway incursions remind the aviation community that
the risk is real:
1977: Tenerife, Canary Islands, 583 fatalities,
2000: Taipei, Taiwan, 83 fatalities,
2001: Milan, Italy, 118 fatalities.
Prevention of runway incursions is of prime importance and must be tackled at all
levels (i.e. airport and aircraft systems). Researches are on going to improve the
airport navigation in terms of safety and efficiency. They include both ground and
on-board systems. AIRBUS actively participates in those researches such as
EMMA2 (European airport Movement and Management by A-SMGCS), which
encompasses new technologies (ATC clearances through CPDLC, on-board traffic
awareness thanks to ADS-B).
Today, two systems are available on AIRBUS aircraft. These two systems are
quite different as they are based on different principles.:
- The On-board Airport Navigation System (OANS) is a new system that
provides visual indications: the aircraft position on an interactive airport
moving map. Therefore, OANS provides the flight crew with a precise aircraft
position on an airport surface. OANS is developed by Thales and is integrated
in the A380 cockpit. In future standards, OANS will take benefit of emerging
technologies (e.g. ground ATC data link clearances, positions of surrounding
aircraft thanks to ADS-B).
- The Runway Awareness and Advisory System (RAAS) is an add-on
module of the EGPWS by Honeywell. It provides aural indications (call-outs)
based on GPS position when operating in the vicinity of a runway (airborne or
on ground). RAAS was certified on A320 and A330/A340 family aircraft in
2007. and on A300/A310 family aircraft in 2008.
The runway excursion is another risk during runway operations (e.g. Toronto,
Canada, 2005). To that end, AIRBUS proposes a Runway end Overrun Warning
(ROW) and a Runway end Overrun Protection (ROP). ROW and ROP provide aural
and visual indications when a risk of runway end overrun is detected during the
landing phase.
In combination with ROW and ROP, AIRBUS also proposes the Brake-To-Vacate
(BTV) function. BTV aims at optimizing the brake utilization and the passenger
comfort when the flight crew selects a runway exit. Some ROW/ROP and BTV
visual indications are provided on the OANS display.
- 5-3 -
5 – Runway surveillance
Getting to grips with Surveillance
On-board Airport Navigation System – OANS
5.1.
DESCRIPTION OF OANS
OANS is a new system introduced by the A380. Its purpose is to locate the aircraft
on an airport map displayed on ND. OANS generates the airport map with its own
Airport Data Base (ADB). OANS improves the flight crew situational awareness
during ground movements on airport surfaces (i.e. ramps, taxis, runways).
OANS is not designed for guidance on ground and does not change the
current taxi procedures. The flight crew must correlate the OANS
indications with the outside visual references.
The expected benefits of OANS are to:
- Reduce the flight crew workload in the day-to-day task of navigating around
complex airfields
- Contribute to safety improvement on airports that become more complex
and busy
- Contribute to potential reduction of taxiing incidents
- Help preventing dangerous errors in surface navigation
- Reduce runway incursion occurrences
- Reduce taxi time, therefore fuel burn and emissions
- Integrate the Brake To Vacate (BTV) function.
5.1.1.
5.1.1.1.
OANS TERMINOLOGY
AIRPORT MAPPING DATA BASE (AMDB)
The Airport Mapping Data Base (AMDB) contains a set of graphical objects that
defines one airport. The accuracy of AMDBs is approximately 5 m (16 ft).
5.1.1.2.
AIRPORT DATA BASE (ADB)
The Airport Data Base (ADB) contains a set of AMDBs and customization settings
(i.e. AMI files). ADB is updated on a 28-day cycle.
Note: OANS does not provide information about temporary airport taxi
restrictions. In addition, OANS may not display recent changes (new buildings or
construction areas). Refer to NOTAM.
5.1.1.3.
AIRPORT MAP
OANS displays on ND a background picture called the Airport Map. OANS
constructs the Airport Map with AMDBs.
- 5-4 -
Getting to grips with Surveillance
5.1.1.4.
5 – Runway surveillance
COVERAGE VOLUME
The coverage volume is a cylinder
centered
on
the
Aerodrome
Reference Point (center of the
airport map) with a radius of 20
NM and a height of 5 000 ft.
5 000 ft
20 NM
Figure 5-1: Coverage volume
5.1.1.5.
AIRPORT MAP DISPLAYED IN ARC AND ROSE NAV MODE
The airport map displayed in ARC or ROSE NAV mode is the nearest airport of
either the departure airport or the destination airport (as entered in FMS). OANS
determines the displayed airport with the coverage volume. If the aircraft is in the
coverage volume of an airport stored in ADB, OANS displays the map of this
airport.
5.1.1.6.
AIRPORT MAP DISPLAYED IN PLAN MODE
The airport map displayed in PLAN mode is either:
- The airport selected by the flight crew, or
- The default airport determined by OANS.
The default airport is either the departure airport or the destination airport. OANS
determines the default airport as the most suitable airport according to the
following parameters:
- The distance between the departure and destination airports
- The distance between the aircraft and the departure or destination airport
- Before or after the transition to the FWS CRUISE phase (i.e. 1 500 fr or 2
min after lift off), particularly for proximate airports (less than 300 NM).
5.1.1.7.
MAP REFERENCE POINT
The Map Reference Point is the reference point to center the airport map when the
flight crew selects the PLAN mode. The Map Reference Point is:
- Either the Aerodrome Reference Point when the aircraft is airborne, or
- The current aircraft position when the aircraft is on ground.
5.1.2.
5.1.2.1.
OANS PRINCIPLES
AIRPORT MOVING MAP
OANS displays an Airport Moving Map on ND at the discretion of the flight crew
in ARC, ROSE NAV or PLAN modes. The displayed airport may be:
- Either manually selected by the flight crew (in PLAN mode only), or
- Automatically selected by OANS from either the departure airport or the
destination airport entered in FMS.
The Airport Moving Map includes comprehensive information about:
- 5-5 -
5 – Runway surveillance
•
•
•
Getting to grips with Surveillance
Runways: QFU, stopways, thresholds, centerline, intersections, markings, exit
lines, shoulders, LAHSO markings, etc
Taxiways: taxi identifiers, guidance lines, holding positions, shoulders, etc
Aprons: parking stand areas, parking stand locations, stand guidance lines,
aerodrome reference points, de-icing areas, etc.
Thanks to a GPS/IRS hybridization, OANS locate the aircraft on the Airport Moving
Map with an accuracy of:
- 10 m (33 ft) for the position
- 0.4° for the heading
- 0.5 kt for the speed.
Nevertheless, the flight crew must always correlate the aircraft position
provided by OANS with outside visual references.
The flight crew interacts with OANS through:
• EFIS CP:
- To select the display mode (ARC, ROSE NAV or PLAN)
- To activate the OANS display on ND (EFIS CP range selector on ZOOM
position)
- To select the display range (5 NM, 2 NM, 1 NM, 0.5 NM, 0.2 NM).
• KCCU:
- To select an airport
- To navigate throughout the Airport Moving Map (drag technique)
- To set some marks (flags and crosses) for drawing a path
- To activate the correct database.
Refer to 5.1.4 – OANS Controls for details.
5.1.2.2.
APPROACHING RUNWAY ADVISORY
OPS+
OANS triggers the APPROACHING RUNWAY advisory each time the aircraft
approaches a runway, a runway intersection, a displaced area, or a stop-way. The
APPROACHING RUNWAY advisory is a pulsing message with the name of the
runway (refer to 5.1.3.5 – Approaching Runway Indication).
Figure 5-2: Detection of runway proximity
- 5-6 -
The detection of an aircraft
approaching a runway is based
on the intersection of the
Aircraft Protection Volume with
the Runway Area. The shape and
the orientation of the Aircraft
Protection Volume depend on
the aircraft dynamics (speed,
acceleration, turn rate). The
Runway Area is an area with a
60-m clearance (200 ft) from
the runway edges.
Getting to grips with Surveillance
5 – Runway surveillance
OANS triggers the APPROACHING RUNWAY advisory 7 s before the aircraft nose
reaches the Runway Area.
OANS
-
displays the APPROACHING RUNWAY advisory when:
The aircraft is on ground
The ground speed is below 40 kt
The aircraft nose is at 7 s from the runway area.
The APPROACHING RUNWAY advisory is displayed for at least 10 s. It is cleared
when:
- The aircraft stops, or
- The aircraft nose has been inside the runway area for 2 s, or
- The aircraft has exited the runway area for 7 s, or
- The advisory has been displayed for more than 30 s.
5.1.3.
OANS INDICATIONS
The OANS indications are displayed on ND and are split into three parts.
The upper banner includes the ground
speed and the airport name.
The airport map is the background of
the ND. The flight crew can interact
with the airport map thanks to the
Interactive Control Menu (refer to
5.1.4.5 – Interactive Control Menu).
The Soft Control Panel provides
several controls (e.g. airport selection,
activation of new ADB, addition of
crosses and flags, etc). Refer to 5.1.4.6
– Soft Control Panel.
Figure 5-3: OANS indications
- 5-7 -
5 – Runway surveillance
5.1.3.1.
Getting to grips with Surveillance
AIRCRAFT SYMBOL
When OANS is active, the aircraft symbol displayed on ND is magenta
instead of yellow. Indeed, as many indications are displayed in yellow, a magenta
aircraft symbol provides a better legibility.
For display ranges from 0.5 to 5 NM, the aircraft symbol is
displayed with the same size (Figure 5-4).
Figure 5-4
Figure 5-5
For the display range of 0.2 NM:
- If the distance from the aircraft nose to the Aircraft
Reference Point is zero, the aircraft symbol is displayed
with the same size as for other display ranges,
- If the distance from the aircraft nose to the Aircraft
Reference Point is not zero, the aircraft symbol is
displayed to scale (Figure 5-5).
Note 1: The distance from the aircraft nose to the Aircraft
Reference Point is defined via a SPP.
Note 2: The aircraft symbol reference point is the
intersection of the two bars. The actual Aircraft
Reference Point is the projection of the 25% MAC on the
aircraft longitudinal axis.
The aircraft symbol is not displayed when the aircraft
position data from either IRS or MMR are not available
or invalid. Consequently, the amber message ARPT NAV POS
LOST is displayed on the airport map.
5.1.3.2.
FMS ACTIVE RUNWAY
The active runway selected in the FMS
flight plan is highlighted on the OANS
display:
- The runway reference (either on
the runway label or the runway
threshold) displayed in green
- A green triangle next to the
active runway threshold.
Figure 5-6: FMS active runway
- 5-8 -
Getting to grips with Surveillance
5.1.3.3.
5 – Runway surveillance
FMS DESTINATION ARROW
The FMS destination arrow indicates the
bearing of the FMS destination airport
when no parts of the airport are visible.
The FMS destination arrow is available
in ARC and ROSE NAV modes.
The following indications are provided:
- The
bearing
of
the
FMS
destination airport with an arrow,
- The ICAO airport code next to
the arrow,
- The distance to the FMS
destination airport in the top
right corner of ND.
Figure 5-7: Destination arrow
Note: The FMS destination arrow aims at the reference point of the FMS
destination airport. When the aircraft is near the FMS destination airport, the
direction of the runway threshold may be significantly different from the direction
of the reference point.
5.1.3.4.
AIRPORT MAP
Flag
The flight crew sets or removes flags along the taxi path with the
Interactive Control Menu or the MAP DATA page of the Soft Control Panel.
Flags are shared on both Captain and First Officer NDs.
Cross
The flight crew sets or removes crosses along the taxi path with the
Interactive Control Menu or the MAP DATA page of the Soft Control Panel.
Crosses are shared on both Captain and First Officer NDs.
The flight crew can use flags as checkpoints to draw the taxiing path and crosses
to identify forbidden taxiways.
- 5-9 -
5 – Runway surveillance
Getting to grips with Surveillance
AMDB elements
Runway elements
Taxiway elements
- 5-10 -
Getting to grips with Surveillance
5 – Runway surveillance
Apron elements
Parking stand elements
Labels
OANS identifies the following elements with a label:
-
Runways,
Taxiways,
Parking stands,
-
Stand lines,
Vertical structures,
Control towers.
P20
Taxiway
example
Bridge symbol
The OANS depicts a bridge as follows.
5.1.3.5.
APPROACHING RUNWAY INDICATION
When the aircraft approaches a runway, OANS provides an APPROACHING
RUNWAY advisory on ND. In ARC or ROSE NAV mode, the APPROACHING
RUNWAY advisory is NN X – MM Y (e.g. 04 L – 22 R).
- NN is the QFU on the left hand side,
- X is the lateral position of the runway NN (void, L, C or R),
- MM is the QFU on the right hand side,
- Y is the lateral position of the runway MM (void, L, C or R).
When approaching two runways (e.g. runway intersection), the APPROACHING
RUNWAY advisory is composed of two lines and displayed as above:
- 5-11 -
5 – Runway surveillance
Getting to grips with Surveillance
The bottom line refers to the nearest runway,
The top line refers to the farthest runway.
-
In addition, the runway(s) designated by the APPROACHING RUNWAY advisory
flash(es) in yellow on the airport map.
In PLAN mode, the APPROACHING RUNWAY advisory is RWY AHEAD: CHANGE
MODE.
Figure 5-8: APPROACHING RUNWAY
advisory in ARC mode
5.1.3.6.
Figure 5-9: APPROACHING RUNWAY
advisory in PLAN mode
OANS MESSAGES
Airport Map
Message
Triggering condition
Color
PLEASE WAIT
White
When the OANS processing time (e.g. map loading)
exceeds 1 second.
ARPT
NOT
ACTIVE F-PLN
IN White
In PLAN mode, when:
- The displayed airport is not one of the airports
entered into the FMS flight plan (departure,
destination, alternates), and
- The current FWS flight phase is neither
APPROACH nor LANDING.
POS Amber
When the aircraft position data from either IRS or
MMR are not available or invalid. The aircraft symbol
is removed from display.
ARPT
LOST
NAV
ERASE ALL FLAGS White
or
ERASE
ALL
CROSSES
When selected from the Interactive Control Menu.
- 5-12 -
Getting to grips with Surveillance
5 – Runway surveillance
Soft Control Panel
Message
Color
Triggering condition
NOT IN [filter] White
DATABASE
In the MAP DATA Page, when the OANS does not
find a map element in the map element list.
[filter] refers to a type of map element (i.e. runway,
taxiway, stand, others).
NOT IN [filter] White
DATABASE
In the AIRPORT SELECTION Page, when the OANS
does not find an airport in the airports list.
[filter] refers to ICAO, IATA or CITY NAME.
DATABASE CYCLE White
NOT VALID
In the STATUS page, when the Airport Data Base is
outdated.
SET PLAN MODE
When the flight crew selects ARC or ROSE NAV
mode and PLAN mode is required (i.e. manually
selected airport not in FMS flight plan).
5.1.4.
5.1.4.1.
White
OANS CONTROLS
EFIS CP RANGE SELECTOR
When in ZOOM position, the EFIS CP range
selector activates the OANS display on ND. The
OANS display is available with the following
range 5 NM, 2 NM, 1 NM, 0.5 NM, 0.2 NM.
These four ranges are available by rotating
the selector counter-clockwise from the
ZOOM position (5NM).
The activation and display of OANS are
independent on both sides (Captain, First
Officer). Each flight crewmember controls the
OANS display on his own ND.
5.1.4.2.
Figure 5-10: A380 EFIS CP
range selector
EFIS CP ND DISPLAY MODE
The OANS display on ND is available in ARC, ROSE
NAV and PLAN modes. These modes remain consistent
with current ND definition when OANS is active.
Figure 5-11: A380 EFIS
CP mode selector
- 5-13 -
5 – Runway surveillance
Getting to grips with Surveillance
ARC mode
The aircraft symbol is fixed at the
bottom of the screen. The Airport
Moving Map moves according to the
aircraft heading and its position.
The Airport Moving Map is orientated in
true or magnetic reference according to
the TRUE/MAG push-button setting.
Figure 5-12: ND ARC mode
ROSE NAV mode
The aircraft symbol is fixed and
centered on the screen. The Airport
Moving Map moves according to the
aircraft heading and its position.
The Airport Moving Map is orientated in
true or magnetic reference according to
the TRUE/MAG push-button setting.
Figure 5-13: ND ROSE NAV mode
PLAN mode
The airport map is fixed, centered
on the Map Reference Point at the
time of the PLAN mode selection,
and orientated towards to the true
north.
The aircraft symbol moves according to
its current heading and position.
Figure 5-14: ND PLAN mode
- 5-14 -
Getting to grips with Surveillance
5.1.4.3.
5 – Runway surveillance
KCCU
The flight crew uses the KCCU to
interact with the MFD and the ND. The
flight crew uses the track ball and the
click button to move the airport map.
5.1.4.4.
MOVE FUNCTION
The MOVE function uses the drag
technique. Press down the KCCU click
button and drag with the KCCU
trackball to move the airport map.
The MOVE function is available in ARC,
ROSE NAV or PLAN mode for three
minutes. However, in PLAN mode, the
displacement is limited: the center of
the background at the time of pressing
down the KCCU click button shall
remain on the screen.
Figure 5-15: KCCU
When the KCCU click button is released:
- In PLAN mode, the new view displayed on ND is kept,
- In ARC or ROSE NAV mode, the ND display progressively comes back to the
initial view.
5.1.4.5.
INTERACTIVE CONTROL MENU
The Interactive Control Menu enables to:
- Set crosses and flags,
- Remove crosses and flags,
- Go to the MAP DATA page,
- Center the airport map on the aircraft
symbol (PLAN mode only).
The flight crew calls the Interactive Control Menu
by clicking with the KCCU anywhere on the airport
map.
Figure 5-16: Interactive
Control Menu
5.1.4.6.
SOFT CONTROL PANEL
The Soft Control Panel (SCP) provides three pages to interact more with the
airport map.
- 5-15 -
5 – Runway surveillance
Getting to grips with Surveillance
The MAP DATA page enables to:
- Access to lists of map elements
(runways,
taxiways,
stands,
deicing areas, terminal buildings,
control towers)
- Center the airport map on a
selected map element
- Set or remove flags or crosses on
a selected map element
- Get more information about a
selected map element
- Insert runway shifts (refer to
5.6.5.1 – Runway Shift).
Figure 5-17: MAP DATA page
The ARPT SEL page enables to:
- Select and display an airport from
the ADB at flight crew’s discretion
(PLAN mode only)
- Get more information about an
airport.
Figure 5-18: ARPT SEL page
The STATUS page enables to:
- Check the ADB validity and serial
number
- Activate a new ADB.
The STATUS page is automatically
displayed at first OANS activation 1 when
the ADB is outdated, missing or
incorrectly loaded.
5.2.
Figure 5-19: STATUS page
OPERATIONAL RECOMMENDATIONS FOR OANS
This paragraph of operational recommendations is intentionally non-exhaustive. For
more recommendations, please check your FCOM and/or FCTM as they are more
frequently updated.
5.2.1.
FOR THE AIRLINE
• Do not use OANS as a guidance tool. OANS is designed to improve the
situational awareness.
• Keep the OANS databases up to date. ADB is updated every 28 days.
Please refer directly to your chart provider.
1
First OANS activation when the aircraft is at the gate.
- 5-16 -
Getting to grips with Surveillance
5 – Runway surveillance
5.2.2.
FOR THE FLIGHT CREW
• Do not use OANS as a guidance tool. OANS is designed to improve the
situational awareness.
• Always correlate the OANS aircraft position with outside visual
references.
• Outside visual references supersede OANS indications in case of
uncertainty.
• Consult NOTAM before taxiing and update the ND airport map with flags
and crosses as necessary. The OANS database may not include recent changes
as it is updated every 28 days.
• Chase doubts in ATC communications (e.g. clearance to cross a runway, to
line up for take-off). Refer to FOBN “Human Performance – Effective
Pilot/Controller Communications” (See AIRBUS References).
• Refer to FOBN “Runway and Surface Operations – Preventing Runway
Incursions” (See AIRBUS References).
• PF: Refer to outside visual references. PNF: Assist PF with OANS
indications as necessary.
• PNF: In reduced visibility conditions, announce when approaching
active runways.
• Before takeoff, when OANS is no longer used, set the minimum ND
range to display the first waypoint after departure, or as required for
weather purposes.
5.3.
REGULATIONS FOR OANS
The interpretation of regulations in this paragraph is limited to AIRBUS aircraft at
the time of writing this brochure.
At the time of writing the present brochure, there is no mandate for the carriage
of OANS.
5.4.
MANUFACTURER FOR OANS
Thalès and AIRBUS jointly developed OANS. At the time of writing the present
brochure, OANS is available on A380 aircraft (basic configuration).
Figure 5-20 provides a simplified view of the OANS architecture.
- 5-17 -
5 – Runway surveillance
Getting to grips with Surveillance
ADIRU
LGERS
FWS
FMS
OANS
MMR
GPS
CMV
EFIS
CP
RMP
ND
HFDR
KCCU
AESS
Figure 5-20: OANS architecture
5.4.1.
UPDATE OF OANS DATABASES
The OANS uses airport databases compliant with ARINC 816 – Embedded
interchange Format for Airport Mapping Database. At the time of writing the
brochure, only Jeppesen provides ARINC 816 ADB and updates online. Contact
your chart provider for more details.
The duration of the upload on aircraft depends on the update file size. The update
may take approximately 15 minutes.
5.5.
FUTURE SYSTEMS
OANS will take benefits of emerging technologies. The new functions under
studies are the integrations of:
- ADS-B IN data to detect aircraft conflicting with own aircraft path.
- The ATSA-SURF application to display surrounding aircraft on the airport
map,
- Data link applications to display NOTAM and ATC ground clearances (e.g.
taxi path on airport map).
- 5-18 -
Getting to grips with Surveillance
5 – Runway surveillance
Please bear in mind…
Description
The On-board Airport Navigation System (OANS) is a new system introduced
by the A380. It improves the flight crew situational awareness during taxi by
locating the aircraft on an airport map.
OANS is NOT designed for guidance on ground and does not change the
current taxi procedures. The flight crew must correlate the OANS
indications with the outside visual references.
Operational recommendations
The main recommendations (but non exhaustive) are:
• OANS is not a guidance tool
• A regular update of OANS Airport Data Base (ADB)
• The check of NOTAM before taxiing
• The correlation of OANS indications with outside visual references.
Refer to 5.2 – Operational Recommendations for OANS.
Regulations
At the time of writing the present brochure, no country has required the carriage
of OANS.
Future systems
The future evolutions of OANS are expected for the integration of:
• The ADS-B data for Traffic Surveillance
• Data link applications to display NOTAM and ATC ground clearances.
- 5-19 -
5 – Runway surveillance
Getting to grips with Surveillance
Runway end Overrun Warning and Protection
(ROW/ROP)
5.6.
DESCRIPTION OF ROW/ROP
The goal of ROW/ROP is to help the flight crew anticipating an overrun of the
runway end during the landing phase. ROW/ROP computes braking distances and
compares them to the Landing Distance Available (LDA) in real time:
- When the aircraft is on final approach: ROW provides aural and visual
indications if the aircraft braking performances are not sufficient to stop on
the runway. The flight crew should perform a go-around.
- When the aircraft is on the runway: ROP provides aural and visual
indications if the current aircraft braking performances are not sufficient to
stop on the runway. ROP applies the maximum braking and the flight crew
shall apply or maintain MAX REVERSE.
Figure 5-21: ROW and ROP concept
The ROW/ROP function is available:
- In all auto brake modes (including Brake To Vacate – BTV, see note below)
- On all runway conditions (dry, wet and contaminated)
- For all aircraft landing configuration (weight, CG, slats/flaps configuration,
etc)
- For any wind and visibility conditions within the aircraft envelope
- With or without autopilot.
At present, ROW and ROP are designed for a utilization with an automatic braking
only. Refer to 5.10 – Future systems.
Note: The goal of BTV is to manage the braking during the landing roll so as to
reach a runway exit selected by the flight crew. BTV benefits are:
- Optimization of the braking energy: It reduces:
Brake temperature (reduction of hydraulic fluid temperature,
reduction of carbon brake oxidation)
Risk of tire deflation
Tire wear
Turn around time (reduction of brake cooling time).
- 5-20 -
Getting to grips with Surveillance
-
-
-
5 – Runway surveillance
Optimization of the runway occupancy: BTV is able to predict and optimize
the Runway Occupancy Time (ROT). When aware of ROT, the ATC controller
is able to optimize the flow of arrivals.
Reduction of environmental impacts: BTV reduces fuel burn thanks to
reduced ROT and reduced use of thrust reversers. BTV also reduces
emission of carbon dust from brake wear.
Improvement of the passenger comfort.
5.6.1.
ROW/ROP PRINCIPLES
The ROW/ROP function:
• Computes the landing distances considering the auto brake is set to HI in:
- Dry conditions: Dry runway with the use of reversers
- Wet conditions: The greatest landing distance between:
Wet runway without the use of reversers
Water contaminated runway with the use of reversers.
• Compares these landing distances to the Landing Distance Available (LDA –
including potential runway shifts) taking into account parameters like:
- Aircraft weight
- Vertical profile (glide slope, 50 ft
- Ground speed
RA, flare)
- Wind
- Landing configuration.
• Triggers an alert when one of the landing distances is greater than LDA.
Definitions of runway states as per EU-OPS1
Contaminated runway: A runway is considered to be contaminated when more
than 25 % of the runway surface area (whether in isolated areas or not) within the
required length and width being used is covered by the following:
i. Surface water more than 3 mm (0.125 in) deep, or by slush, or loose
snow, equivalent to more than 3 mm (0.125 in) of water, or
ii. Snow which has been compressed into a solid mass which resists
further compression and will hold together or break into lumps if picked
up (compacted snow), or
iii. Ice, including wet ice.
Dry runway: A dry runway is one which is neither wet nor contaminated, and
includes those paved runways which have been specially prepared with grooves or
porous pavement and maintained to retain “effectively dry” braking action even
when moisture is present.
Wet runway: A runway is considered wet when the runway surface is covered with
water, or equivalent, less than specified in [contaminated runway] or when there is
sufficient moisture on the runway surface to cause it to appear reflective, but
without significant areas of standing water.
- 5-21 -
5 – Runway surveillance
5.6.1.1.
Getting to grips with Surveillance
AUTOMATIC DETECTION OF THE RUNWAY FOR LANDING
When the destination airport is known (i.e. in the FMS flight plan), the runway for
landing is automatically detected. The auto-detection of the landing runway aims
at coping with mistakes or omissions of the flight crew, or late runway changes.
When the flight crew selects:
- An auto brake mode (except BTV), the automatic detection of the landing
runway is active between 500 ft and 300 ft.
- BTV, the automatic detection of the landing runway is active at 300 ft.
If the automatic detection of the landing runway fails (i.e. no detected runway), the
ROW/ROP function is lost. Besides, if the ROW/ROP function is lost, the BTV
function is lost.
5.6.1.2.
ROW ARMED
ROW arms when the landing runway is automatically detected (refer to 5.6.1.1 –
Automatic Detection of the Runway for Landing). Therefore:
- OANS highlights QFU of the automatically detected runway.
- ROW computes, in real time, the minimal braking distances in dry and wet
conditions.
- If the flight crew selects BTV, OANS displays the braking distances
computed in dry and wet conditions (DRY and WET lines – refer to 5.6.3.1
– ROW Indications When Armed) over the landing runway. As ROW
computes the minimal braking distances in real time, OANS adjusts the DRY
and WET lines on the landing runway.
5.6.1.3.
ROW ENGAGED
ROW engages when the minimal braking distance computed in dry or wet
conditions exceeds LDA. It means that ROW engages when the DRY or WET line
(in BTV mode only) exceeds the runway end on OANS display.
When ROW engages, it triggers an alert with visual and/or 2 aural indications:
- When the braking performances computed in wet conditions are not
sufficient and the runway is currently wet, the flight crew should perform a
go-around.
- When the braking performances computed in wet conditions are not
sufficient and the runway is currently dry, the flight crew should disregard
the alert.
- When the braking performances computed in dry conditions are not
sufficient, the flight crew should perform a go-around.
ROW disengages and disarms when the flight crew performs a go-around.
ROW disengages (but remains armed) when updated braking distances in dry and
wet conditions do not exceed LDA anymore.
2
ROW triggers an aural alert only below 200 ft RA when the braking performances in dry conditions
are not sufficient.
- 5-22 -
Getting to grips with Surveillance
5.6.1.4.
5 – Runway surveillance
ROP ARMED
ROP arms when the auto brake engages. The auto brake engages in landing mode
when:
- The ground spoilers extend and the nose landing gear is on ground, or
- 5 seconds after the ground spoiler extension, whichever occurs first.
When ROP arms:
- ROP computes, in real time, a braking distance to reach a target speed that
equals to:
0 kt if the flight crew selected an auto brake mode (except
BTV), or
10 kt if the flight crew selected BTV.
- OANS displays this computed braking distance over the landing runway
(STOP bar – refer to 5.6.3.3 - ROP Indications When Armed).
ROP remains armed until the flight crew disconnects the auto brake.
5.6.1.5.
ROP ENGAGED
ROP engages:
- When the STOP bar exceeds the runway end, or
- As soon as the auto brake engages if ROW had previously engaged between
the deployment of ground spoilers and the activation of auto brake.
Therefore, ROP:
- Controls the maximum braking performance 3 (same as in RTO mode).
- Triggers aural and visual indications to apply or maintain MAX REVERSE.
ROP disengages (but remains armed) when the STOP bar does not exceed the
runway end anymore. Therefore, the auto brake reverts to the mode selected by
the flight crew.
5.6.2.
AUTO BRAKE DISCONNECTION
The flight crew disconnects the auto brake by:
- Pressing the brake pedals, or
- Pressing the A/THR instinctive disconnect pushbutton on the thrust levers,
or
- Switching the auto brake mode selector to DISARM.
Pressing the A/THR instinctive disconnect pushbutton on the thrust levers is a new
method to disconnect the auto brake introduced by ROW/ROP/BTV.
The auto brake automatically disconnects when the aircraft reaches:
- 0 kt if the flight crew selected an auto brake mode (except BTV), or
- 10 kts if the flight crew selected BTV.
3
If the ROW/ROP function is lost during the period when ROP is engaged, the auto brake maintains the
maximum braking performance.
- 5-23 -
5 – Runway surveillance
5.6.3.
5.6.3.1.
Getting to grips with Surveillance
ROW/ROP INDICATIONS
ROW INDICATIONS WHEN ARMED
If the flight crew selected an auto brake mode (except BTV), ROW
highlights the runway QFU.
If the flight crew selected BTV, ROW displays the DRY and WET lines in
magenta.
Figure 5-22: ROW armed with auto
brake (except BTV) selected
Figure 5-23: ROW armed with BTV
selected
Note 1: ROW computes the braking distances in real time. Therefore, the DRY
and WET lines move along the runway according to the current flight conditions
(Vapp, landing configuration, aircraft position, ground speed, wind, aircraft
weight).
Note2: The green triangle refers to the runway selected in the FMS.
5.6.3.2.
ROW INDICATIONS WHEN ENGAGED
•
Computed braking performances not sufficient in wet conditions
On ND
If the flight crew selected an auto brake mode (except BTV), there is no
additional ROW indication on ND when ROW engages. Refer to Figure 5-22.
If the flight crew selected BTV, when ROW engages, it displays:
- The WET bar in amber
- The path between the runway end and the WET bar in amber.
- 5-24 -
Getting to grips with Surveillance
5 – Runway surveillance
On PFD
ROW displays an amber message IF
WET: RWY TOO SHORT on PFD,
regardless of the selected auto brake
mode.
Figure 5-24: ND – ROW engaged with
BTV selected (wet conditions)
Figure 5-25: PFD – ROW engaged
•
Computed braking performances not sufficient in dry conditions
On ND
If the flight crew selected an auto brake mode (except BTV), there is no additional
ROW indication on ND when ROW engages. Refer to Figure 5-22.
If the flight crew selected BTV, when ROW engages, it displays:
- The WET and DRY lines in red
- The path between the runway end and the WET and DRY lines in red.
On PFD
ROW displays a red message RWY TOO
SHORT on PFD, regardless of the
selected auto brake mode. In case of
wind
shear,
the
red
message
WINDSHEAR has priority.
Figure 5-26: ND – ROW engaged with
BTV selected (dry conditions)
Figure 5-27: PFD – ROW engaged
- 5-25 -
5 – Runway surveillance
Getting to grips with Surveillance
RUNWAY TOO SHORT
ROW triggers the aural alert RUNWAY TOO SHORT below 200 ft RA.
5.6.3.3.
ROP INDICATIONS WHEN ARMED
If the flight crew selected an auto brake mode (including BTV), ROP displays the
STOP bar.
Figure 5-28: ROP armed with auto
brake (except BTV) selected
Figure 5-29: ROP armed with BTV
selected
Note: The STOP bar moves along the runway as the braking distance is computed
in real time according to the current flight parameters.
5.6.3.4.
ROP INDICATIONS WHEN ENGAGED
When ROP detects a runway end overrun, it:
- Displays the computed braking distance in red on ND
- Displays the red message MAX REVERSE on PFD.
Refer to Figure 5-30 and Figure 5-31.
MAX REVERSE or KEEP MAX REVERSE
ROP triggers the aural alert:
- MAX REVERSE continuously until the complete deployment of reversers, or
- KEEP MAX REVERSE one time:
At 80 kt if the flight crew fully deployed the reversers and ROP
still detects a runway end overrun, or
Below 80 kt if the flight crew fully deploys the reversers below
80 kt and ROP still detects a runway end overrun.
- 5-26 -
Getting to grips with Surveillance
5 – Runway surveillance
Figure 5-31: PFD – ROP engaged
Figure 5-30: ND – ROP engaged
5.6.4.
INDICATIONS FOR AUTO BRAKE DISCONNECTION
When the flight crew deliberately disconnects the auto brake (i.e. press two times
on the A/THR instinctive disconnect pushbutton), there is no indication in the
cockpit.
When the auto brake is inadvertently or automatically disconnected, aural and
visual indications are provided.
PFD
ECAM
Single chime
Figure 5-32: Indications for inadvertent or automatic auto brake disconnection
In addition, all ROW, ROP and BTV indications are removed from display.
5.6.5.
5.6.5.1.
ROW/ROP CONTROLS
RUNWAY SHIFT
The flight crew inserts runway shifts via
the OANS MAP DATA page (Figure 5-33
to Figure 5-35). The flight crew can
insert runway shifts for one runway only
at a time.
Used unit (m or ft) is defined by pinprogramming.
- 5-27 -
Figure 5-33: Select LDG SHIFT
5 – Runway surveillance
Getting to grips with Surveillance
Figure 5-34: Enter runway shifts
Figure 5-35: Runway shifts entered
Note: Runway shifts are not erased at the end of the flight. They remain active
for the next flight unless the next flight crew deletes them.
5.7.
OPERATIONAL RECOMMENDATIONS FOR ROW/ROP
5.7.1.
FOR THE AIRLINE
• Train your flight crews to properly operate ROW and ROP. Particular
attention should be paid to task sharing, monitoring of ROW/ROP indications
during approach.
5.7.2.
FOR THE FLIGHT CREW
• Be sure to understand ROW and ROP indications. The DRY and WET lines
and the STOP bar move along the runway according to the current flight
conditions. Overrun situations can be anticipated thanks to these indications.
• Monitoring of the DRY and WET lines under 500 ft is at PNF’s discretion. PNF
should concentrate on basic flying parameters.
• Use the A/THR instinctive disconnect pushbutton on the thrust levers to
disconnect the auto brake.
5.8.
REGULATIONS FOR ROW/ROP
The interpretation of regulations in this paragraph is limited to AIRBUS aircraft at
the time of writing this brochure.
At the time of writing the present brochure, there is no mandate for the carriage
of the ROW/ROP function.
- 5-28 -
Getting to grips with Surveillance
5.9.
5 – Runway surveillance
MANUFACTURERS FOR ROW/ROP/BTV
AIRBUS developed ROW and ROP that are distributed among several systems.
They are optional functions and are simultaneously activated via pinprogramming.
Figure 5-36 provides a simplified view of the ROW/ROP architecture.
FMS
OANS
BCS
BCS
AFS
FWS
KCCU
ND
PFD
EWD
Brake Pedals
A/THR DISC
P/B
Auto Brake
Mode Selector
Figure 5-36: ROW/ROP/BTV architecture
5.10. FUTURE SYSTEMS
AIRBUS studies the extension of ROW/ROP to the manual braking mode.
- 5-29 -
5 – Runway surveillance
Getting to grips with Surveillance
Please bear in mind…
Description
The ROW and ROP functions help the flight crew anticipating an overrun of the
runway end at landing. During the final approach, ROW provides aural and visual
indications that invite the flight crew to consider a go around. On the runway, ROP
provides aural and visual indications for the settings of thrust reversers.
ROW/ROP improves the flight crew awareness regarding risks of runway end
overrun.
ROW and ROP are optional functions and used in conjunction with OANS.
Operational recommendations
The main recommendations (but non exhaustive) are:
• The correct understanding of ROW and ROP indications
• The proper disconnection of the auto brake.
Regulations
At the time of writing the present brochure, no country has required the carriage
of the ROW/ROP function.
Future systems
AIRBUS studies the extension of ROW/ROP to the manual braking mode.
- 5-30 -
Getting to grips with Surveillance
5 – Runway surveillance
Runway Awareness and Advisory System – RAAS
5.11. DESCRIPTION OF RAAS
RAAS is an add-on module of the Honeywell EGPWS. It uses the GPS position
and the runway data of the EGPWS terrain database. The RAAS Configuration
Database (RCD) enables some customization (e.g. GPS antenna position, female
or male voice, units in feet or meters) and the settings of some options (e.g.
activation/deactivation of some call-outs, audio volume). The RAAS uses the
EGPWS resources to produce the call-outs.
The RAAS is capable of 10 different call-outs. There are two certified
configuration on AIRBUS aircraft that includes 3 call-outs only (the second
certified configuration includes call-outs with lower audio volume). These call-outs
are triggered on ground only. The selection of these 3 call-outs is coming out from
a long period of evaluations through flight tests and simulator sessions. It has to
be noted that a major airline selected the same set of call-outs as a result of an
evaluation of several months on other aircraft model.
The following sections describe only the call-outs certified on AIRBUS aircraft. The
first two call-outs are routine advisories as the RAAS systematically triggers
them on each flight. The last call-out is a non-routine advisory as the RAAS
only triggers it when specific conditions are met. All these call-outs are triggered
on ground.
5.11.1.
APPROACHING RUNWAY – ON GROUND ADVISORY – ROUTINE
5.11.1.1.
PURPOSE
« APPROACHING
« APPROACHING
The Approaching Runway
ONE FOUR »
THREE TWO »
advisory informs the flight
crew that the aircraft is Figure 5-37: RAAS Approaching Runway advisory
approaching a runway edge.
The advisory announces the closest runway end (refer to Figure 5-37).
5.11.1.2.
•
•
•
TRIGGERING CONDITIONS
Ground speed is less than 40 kt
Aircraft is within a specified distance to the runway. This distance is a
function of ground speed and closure angle. The higher the ground speed,
the earlier the advisory.
If more than one runway meet the conditions (e.g. two runways within +/20° of heading of each other), the advisory is APPROACHING RUNWAYS.
The RAAS triggers the advisory one time when the aircraft approaches a runway.
- 5-31 -
5 – Runway surveillance
5.11.2.
Getting to grips with Surveillance
ON RUNWAY ADVISORY – ROUTINE
5.11.2.1.
PURPOSE
The On Runway advisory
informs the flight crew on
which runway the aircraft is
lined-up.
« ON RUNWAY
ONE FOUR »
Figure 5-38: RAAS On Runway advisory
Note: The AIRBUS flight tests revealed that the On Runway advisory may
interfere with the ATC take-off clearance. The On Runway advisory may partially
or completely overlap the clearance. This interference may be considered as a
nuisance in daily routine operations, especially when weather and visibility are
fine. But it was admitted the On Runway advisory to be helpful, especially when
weather and/or visibility are unfavorable. To mitigate the nuisance, the latest
certified RCD on AIRBUS aircraft permits to significantly reduce the audio volume
of routine advisories.
5.11.2.2.
TRIGGERING CONDITIONS
• Aircraft enters a runway
• Aircraft heading is within +/- 20° of runway heading.
The RAAS triggers the advisory one time when the aircraft enters a runway.
5.11.3.
TAKEOFF ON TAXIWAY ADVISORY – NON-ROUTINE
5.11.3.1.
PURPOSE
The Takeoff On Taxiway
advisory informs the flight
crew of excessive taxi speed
or inadvertent takeoff on
taxiway.
« ON TAXIWAY !
ON TAXIWAY ! »
Figure 5-39: RAAS Take-Off On Taxiway advisory
Note: To balance the noise from the engine power setting, the volume level of the
Take-Off On Taxiway advisory is increased by +3dB compared to EGPWS call-out
volume level.
5.11.3.2.
•
•
TRIGGERING CONDITIONS
Ground speed is more than 40 kt
Aircraft is not on a runway.
The RAAS uses a runway database. Therefore, the RAAS is not able to locate
taxiways. Rolling on a pavement that is not a runway at high speeds triggers the
Take-Off On Taxiway advisory.
- 5-32 -
Getting to grips with Surveillance
5 – Runway surveillance
5.12. OPERATIONAL RECOMMENDATIONS FOR RAAS
From the AIRBUS flight test campaign, the set of advisories has been limited to
three (Approaching Runway, On Runway, Take-Off On Taxiway). AIRBUS has no
specific recommendations on RAAS operations.
• Refer to FOBN “Runway and Surface Operations – Preventing Runway
Incursions” (See AIRBUS References).
Note: The certified AIRBUS RCD enables only RAAS advisories triggered on
ground. Therefore, RAAS advisories would unlikely interfere with other call-outs
on ground. Indeed, call-outs triggered on ground in AIRBUS cockpits are:
- Predictive Wind Shear (PWS) alerts from Weather Radar (WXR), and
WXR alerts have priority over EGPWS ones,
- V1 and RETARD call-outs, and the RAAS does not trigger advisories
at the same aircraft speeds.
5.13. REGULATIONS FOR RAAS
The interpretation of regulations in this paragraph is limited to AIRBUS aircraft at
the time of writing this brochure.
At the time of writing the present brochure, there is no mandate for the carriage
of RAAS.
5.14. MANUFACTURER FOR RAAS
The RAAS is part of the Honeywell EGPWS. Additional information is available at
http://www.honeywell.com/sites/aero/Egpws-Home3_CB54AACBB-D557-208D8CE0-EC44CECAAB3B_HD821C499-7201-CF0B-5533-6EFD92534345.htm.
The RAAS requires recent EGPWS software version and terrain database.
Refer to the Honeywell RAAS Product Description available at the link mentioned
above.
5.15. FUTURE SYSTEMS
At the time of writing the present brochure, no evolutions are expected, from
AIRBUS perspective, for RAAS in terms of new functions.
- 5-33 -
5 – Runway surveillance
Getting to grips with Surveillance
Please bear in mind…
Description
The Runway Awareness and Advisory System (RAAS) is one system that
fulfills the Runway Surveillance function. It is a module of the Honeywell EGPWS.
The RAAS provides advisories about the aircraft position on or out the runway
thanks to the EGPWS runway database. Therefore, the RAAS is not able to
locate taxiways. Anyway, it is able to identify when the aircraft is rolling on a
pavement that is not a runway at high speed.
AIRBUS aircraft had been certified with three call-outs out of ten: Approaching
Runway, On Runway and Take-Off On Taxiway.
The RAAS requires recent EGPWS software version and terrain database.
Operational recommendations
AIRBUS has no recommendations on RAAS operations.
Regulations
At the time of writing the present brochure, no country has required the carriage
of RAAS.
Future systems
At the time of writing the present brochure, no evolutions are expected, from an
AIRBUS perspective, for RAAS in terms on new functions.
- 5-34 -
Getting to grips with Surveillance
6 – Weather surveillance
6. WEATHER SURVEILLANCE
6.1
6.1.1
6.1.1.1
6.1.1.2
6.1.1.3
6.1.1.4
6.1.1.5
6.1.1.6
6.1.1.7
6.1.1.8
6.1.2
6.1.2.1
6.1.2.2
6.1.3
6.1.3.1
6.1.3.2
6.1.3.3
6.1.3.4
6.1.4
6.1.5
6.1.5.1
6.1.5.2
6.1.5.3
6.1.5.5
6.1.6
6.1.7
6.1.7.1
6.1.7.2
6.1.8
6.2
6.2.1
6.2.1.1
6.2.1.2
Description of Weather Radar
Radar Theory
Reflectivity of Water Molecules
Reflectivity of Thunderstorms
Frequency Band
Gain
Antenna
Radar Beam
Interfering Radio Transmitters
Radiation Hazards
Weather, Turbulence and Wind Shear Detection
Coverage
Wind Shear Detection
Weather Radar Operating Modes
WX Mode
WX+T, WX/TURB or TURB Mode
MAP Mode
PWS Mode
Reactive Wind Shear
Weather Radar Functions per Manufacturer
Autotilt (Honeywell)
Multiscan (Rockwell Collins)
Ground Clutter Suppression – GCS (Rockwell Collins)
GAIN PLUS (Rockwell Collins)
Reactive Wind Shear Indications
Weather Radar Indications
Weather Radar Messages
Wind Shear Indications
Weather Radar Controls
Operational Recommendations for Weather Radar
Weather Radar Operations
For the Airline
For the Flight Crew
- 6-1 -
6-3
6-3
6-3
6-4
6-5
6-5
6-6
6-7
6-11
6-11
6-12
6-12
6-13
6-13
6-13
6-13
6-14
6-14
6-16
6-16
6-17
6-18
6-19
6-20
6-23
6-23
6-25
6-25
6-26
6-27
6-27
6-27
6-27
6 – Weather surveillance
6.2.2
6.2.2.1
6.2.2.2
6.3
6.4
6.4.1
6.4.2
6.5
6.5.1
Getting to grips with Surveillance
Wind Shear
For the Airline
For the Flight Crew
Regulations for Weather Radar
Manufacturers for Weather Radar
Honeywell RDR-4B
Rockwell Collins WXR 701X and WXR 2100
Future Systems
Honeywell RDR 4000
- 6-2 -
6-28
6-28
6-28
6-29
6-31
6-31
6-31
6-32
6-32
Getting to grips with Surveillance
6 – Weather surveillance
Turbulence, wind shear, hail, and thunderstorm are identified as the causes of
major incidents or accidents, especially during final approach and take-off. The
awareness of these meteorological phenomena improves the flight safety thanks
to the weather radar.
At the time of writing the brochure, three types of weather radar are available on
Airbus aircraft:
- Conventional weather radar: The weather display is synchronized with the
movement of the radar antenna.
- Weather radar with an automatic tilt 1: It is a radar capable to compute
automatically a tilt angle.
- Weather radar using a buffer: The weather information from the radar
antenna is stored in a buffer. Weather information only applicable for display
is extracted from this buffer. Weather radars that use a buffer are Rockwell
Collins Multiscan and the AESS weather radar from Honeywell.
The
present
chapter
describes
weather
radars
available
on
A300/A310/A320/A330/A340 aircraft. For the Honeywell weather radar of AESS
available on A380 aircraft, refer to 7 – Aircraft environment Surveillance.
6.1.
DESCRIPTION OF WEATHER RADAR
Thanks to the characteristics of weather radar pulses, the weather radar detects
precipitations, wind shears, turbulence and prominent terrains. The weather radar
also provides indications and/or alerts to avoid them. It has to be noted that
the weather radar detects wet meteorological phenomena only: it means
that the weather radar does not detect dry phenomena like Clear Air Turbulence
(CAT).
The present chapter provides a basic knowledge about weather radar physics and
describes the functions proper to each weather radar type. The description is
common to all weather radar types, except when specified. The Appendix G –
Aviation meteorology reminders also provides some reminders about
meteorological phenomena linked to flight operations.
Note: for A380 aircraft, please refer to 7.1.4 – Weather Radar Function. However,
the weather radar basic principles on-board the A380 remain identical to the ones
described in this chapter.
6.1.1.
6.1.1.1.
RADAR THEORY
REFLECTIVITY OF WATER MOLECULES
The weather radar properly detects rains or wet turbulence. Indeed, water
molecules in liquid state reflects radar pulses more than ice crystals do. Based on
this principle, the reflectivity of precipitations depends on their nature. The radar
pulse weakly reflects on dry snow and dry hail. In addition, wet hail
presents a higher reflectivity than rain thanks to the size of hailstone
combined with the presence of liquid water molecules on their surface. Most of the
1
Autotilt is a registered trademark of Honeywell.
- 6-3 -
6 – Weather surveillance
Getting to grips with Surveillance
time, the radar pulse is not able to penetrate wet hail. The weather behind wet
hail is often hidden.
Similarly
to
wet
hail,
stratiform rain in the vicinity
(at or 3000 ft below) of the
freezing level returns a large
portion of the radar pulse.
Indeed, in this area, ice crystals
start to melt and are covered of
water.
Figure 6-1: Reflectivity of precipitations
6.1.1.2.
REFLECTIVITY OF THUNDERSTORMS
Based on the principle described above, weather radars are optimized to detect
rains. Consequently, thunderstorms may be divided into four layers according to
the reflectivity of each layer.
•
•
•
•
The turbulence dome defines an
area of very severe turbulence. It
can reach several thousand feet
above the visible top, when the
thunderstorm is growing
The upper part above the
altitude of –40°C (if applicable)
contains ice crystals only. It reflects
a very small portion of the radar
pulse. This part may be invisible on
the weather radar image whereas it
is clearly visible through the
windshield
The intermediate part from the
freezing level up to the altitude
of –40°C contains ice crystals and
super-cooled water. The supercooled water reflects a portion of
the radar pulse. Ice crystals absorb
the remainder of the radar pulse
The lower part up to the
freezing
level
is
the
most
reflective part of the thunderstorm
due to the heavy rain.
Figure 6-2: Thunderstorm
The radar or wet top is the highest portion of the thunderstorm the weather
radar can detect. It separates the intermediate part from the top part of a
thunderstorm.
The visible top is the top of the thunderstorm upper part.
- 6-4 -
Getting to grips with Surveillance
6.1.1.3.
6 – Weather surveillance
FREQUENCY BAND
As a general physics rule, the propagation of a wave is closely linked to its length
or frequency.
As a reminder: wavelength
=
wave celerity
wave frequency
Higher the frequency, shorter the wavelength, weaker the propagation.
The weather radar is optimized to detect rains. Therefore, the frequency of the
radar pulse is approximately 9333 MHz. Consequently, the weather radar is not
able to detect fog, light rains, or dry clouds. In addition, the weather radar may
not detect weather behind a heavy rain.
Figure 6-3 gives an idea of
the rain reflectivity per
frequency band. It has to be
noted that cloudburst (rain
more than heavy) may block
pulses of ground radars.
Therefore, each time an
ATC controller announces
a heavy rain from his
radarscope,
the
flight
crew should consider this
heavy rain as extremely
severe.
Figure 6-3: Reflectivity per frequency band
6.1.1.4.
GAIN
The weather radar measures the precipitation rate (millimeters per hour). For the
calibrated gain, the precipitation rates are color-coded as follows:
Color
Precipitation
Precipitation
rate (mm/h)
Reflectivity
factor 2 (dBZ)
PR < 1
Z < 20
Black
Green
Weak
1 < PR < 4
20 < Z < 30
Yellow
Moderate
4 < PR < 12
30 < Z < 40
Red
Strong and higher
12 < PR
40 < Z
Magenta
Turbulence
5 m/s < ΔPR
N/A
2
The reflectivity factor Z measures the strength of the radar return in a volume of precipitation. Z
depends on the number and the size of raindrops in a volume, and is expressed in decibels (dBZ).
- 6-5 -
6 – Weather surveillance
Getting to grips with Surveillance
The weather radar displays turbulence in magenta each time the variation of
precipitation rates (ΔPR) is greater than 5 m/s. It should be noted that Clear Air
Turbulence (CAT) is not detected.
A variation of the gain by 10dBZ implies a variation of display by one
color level (e.g. green becomes yellow with a variation of +10dBZ, red becomes
yellow with a variation of –10dBZ).
Note: Turbulence remains magenta regardless of the gain setting.
6.1.1.5.
ANTENNA
Parabolic and Flat Antennas
6.1.1.5.1.
There are two types of weather radar antenna: parabolic for the first generation
of weather radar (on A300/A310 and former A320 aircraft) and flat for the recent
generation (on A320/A330/A340 aircraft).
•
Parabolic Antenna
The parabolic antenna produces a wide
main beam and large side lobes.
Consequently, the large side lobes
present the advantage of scanning
below the aircraft, but also drawbacks
like ground returns on display and the
inability to reliably detect wind shears.
•
Flat Antenna
The main beam from a flat antenna is
more contained than the one from a
parabolic antenna. Moreover, side lobes
are smaller. With a flat antenna, the
display is more accurate, ground
returns are significantly reduced, but
the capability to scan below the aircraft
is lost.
6.1.1.5.2.
Side Lobes
Significant side lobes may be produced by parabolic antennas or may be the
result of damages/degradations on the antenna or the radome.
- 6-6 -
Getting to grips with Surveillance
6 – Weather surveillance
•
Cat’s Eyes Phenomenon
The Cat’s eyes (also known as Altitude
rings or Ghost targets) appear at +/45° between 4 and 8 NM when the
aircraft is at approximately 3000 ft
above the ground. They are the results
of ground returns due to side lobes.
They are not visible when the aircraft is
on ground.
Tips: Cat’s eyes with gain in CAL
position
Cat’s eyes should not be visible
when the gain is set to CAL
position. If Cat’s eyes are visible with
the CAL setting, damages/degradations
on antenna or radome should be
considered.
•
False Wind Shear Alerts
The weather radar may wrongly interpret strong returns due to large side lobes as
wind shears. This explains why the first generation of weather radars is not able
to detect wind shears.
6.1.1.5.3.
Antenna Stabilization
The antenna stabilization maintains the antenna scanning parallel to the
horizon regardless of the aircraft attitude. The antenna is stabilized in roll
and pitch. Thanks to the antenna stabilization, the display of ground returns on
ND does not change when the aircraft attitude change.
If the antenna stabilization fails, the radar antenna scans parallel to the wings
per default. Consequently, if the aircraft turns, ground returns may cover half of
the display (on the side of the turn).
Figure 6-4: Antenna stabilization limits
6.1.1.6.
6.1.1.6.1.
RADAR BEAM
Diameter and Resolution
•
Diameter
The aperture of the radar beam is approximately 3.5°.
- 6-7 -
6 – Weather surveillance
Getting to grips with Surveillance
The beam diameter at a given
distance may be approximately
determined by the following
formula:
Beam diameter [ft] =
3.5 x (Distance [NM] + “00”)
Example:
Distance = 50 NM
Distance + “00” = 5 000
Beam diameter = 17 500 ft
Figure 6-5: Beam diameters
•
Range Resolution
The radar beam emits pulses to detect weather. For long-range detection (more
than approximately 80 NM), high-energy pulses (i.e. wide pulses) are transmitted
to compensate the beam attenuation. Therefore, pulses for long-range detection
are wider than pulses for short-range detection.
- When the pulse width is shorter than the distance between two
precipitations, the weather radar detects two precipitations.
- When the pulse width is longer than the distance between two precipitations,
the weather radar detects one precipitation.
Shorter the pulse (or shorter the range), higher the range resolution.
Consequently, the weather
radar
may
display
two
distinct
precipitations
detected at long range as a
single block. And when the
aircraft gets closer to the
precipitations, the weather
radar
may
display
the
precipitations as two distinct
blocks.
•
Azimuth Resolution
With an aperture of 3.5°, the
width
of
radar
beam
significantly increases with
the range. An analysis similar
to the range resolution may
be made with the width of
the radar beam.
Thinner the beam width
(or shorter the range),
higher
the
azimuth
resolution.
Figure 6-6: Range and Azimuth resolutions
- 6-8 -
Getting to grips with Surveillance
6.1.1.6.2.
6 – Weather surveillance
Attenuation
•
Beam Attenuation
The energy of the radar pulse attenuates when the radar pulse goes away and
returns back to the radar antenna (i.e. absorption and refraction). If the weather
radar does not compensate the beam attenuation, the weather radar may display
a precipitation:
- As weak (i.e. green) when the aircraft is far from the precipitation
- As strong (i.e. red) when the aircraft is approaching the precipitation.
•
Path Attenuation
Some precipitations may be
so strong that the radar
beam is not able to penetrate
them. Consequently, they
mask the weather behind
them. This is called the path
attenuation
or
radar
shadow.
6.1.1.6.3.
Figure 6-7: Path attenuation or Radar shadow
Sensitivity Time Control
The
Sensitivity
Time
(STC)
Control
compensates the beam
attenuation within 80 NM.
The STC increases the radar
sensitivity over time while
the aircraft is getting closer
to a precipitation.
Figure 6-8: Sensitivity Time Control
Thanks to the STC, the display of a given precipitation is more accurate within 80
NM and should not vary in colors (provided that the intensity of the precipitation
is constant) when the aircraft is getting closer to the precipitation.
- 6-9 -
6 – Weather surveillance
Getting to grips with Surveillance
Conventional radar
Radar with Sensitivity Time Control
Figure 6-9: Weather displays with and without STC
6.1.1.6.4.
Weather, Ground and Sea returns
•
Weather/Ground Returns
The weather radar links radar returns to a color according to their intensity. As
ground returns are of high intensity, colors are then useless to distinguish
weather returns from ground ones. The shape of displayed patterns and the use
of tilt help in determining the nature of returns (weather or ground):
- Ground returns: sharp or broken shape, significant color variation
when the tilt setting changes
- Weather returns: large and diffuse shape, light color variation
when the tilt setting changes.
•
Sea Returns
Returns of large bodies of water (e.g. sea, lake) are different according to the
state of the water surface and the direction of waves. Radar returns are weak
from calm waters but are strong if the radar pulses hit the downwind side of
waves on a choppy water.
Figure 6-10: Radar returns on calm and choppy waters
- 6-10 -
Getting to grips with Surveillance
6.1.1.7.
6 – Weather surveillance
INTERFERING RADIO TRANSMITTERS
Radio transmitters that operate a
frequency close to the weather radar
one (i.e. 9333 MHz) can interfere and
produce
unusual
displays.
Those
transmitters may be military radar,
radar-jamming equipment, or satellite
ground earth station.
The Rockwell Collins WXR 2100
weather radar includes a filter that
partly attenuates these interferences.
Figure 6-11 shows a display when the
radar does not filter the interferences
from radio transmitters.
Figure 6-11: Interfering radio
transmitters
6.1.1.8.
RADIATION HAZARDS
Before activating the weather radar, make sure that:
• No one is within a sector defined by a radius of 5 m and +/-135°
from the aircraft centerline,
• No large metallic obstacle is within a sector defined by a radius of 5
m and +/- 90° from the aircraft centerline.
Refer to FAA AC 20-68B “Recommended Radiation Safety Precautions for Ground
Operation of Airborne Weather Radar”.
As a reminder, the following
table gives the fuselage cross
sections of AIRBUS aircraft. It
gives an idea about the
radiation hazard clearance.
Aircraft
A300/A310
A320 Family
A330/A340
A380*
Fuselage
diameter
5.64 m
3.85 m
5.64 m
7.14 m
* for A380 aircraft, it is the
fuselage width.
Figure 6-12: Radiation hazard boundary
- 6-11 -
6 – Weather surveillance
6.1.2.
6.1.2.1.
Getting to grips with Surveillance
WEATHER, TURBULENCE AND WIND SHEAR DETECTION
COVERAGE
The weather and turbulence
detections
(Honeywell
and
Rockwell Collins weather radars)
cover an area as defined in.
Figure 6-13.
Figure 6-13: Radar coverage
For Honeywell radar only, the
horizontal plane is divided into
five sectors (dashed on Figure
6-13) for Autotilt purposes.
Refer to 6.1.5.1 – Autotilt
(Honeywell).
Note: For any radars, the tilt angle refers to
the horizon and not to the longitudinal
centerline.
Figure 6-14: Pitch and Tilt
The wind shear detection covers a
sector of 60° from the centerline on
either side of the aircraft.
Wind shear events are displayed
within a sector of:
- 30° for Rockwell Collins
radars,
- 40° for Honeywell radars,
from the centerline on either side of
the aircraft.
Figure 6-15: Wind shear detection range
- 6-12 -
Getting to grips with Surveillance
6.1.2.2.
6 – Weather surveillance
WIND SHEAR DETECTION
Two kinds of protection are
provided against wind shears:
- The
Predictive
Wind
Shear (PWS) performed
by the weather radar to
avoid wind shear events,
- The
Reactive
Wind
Shear performed by the
flight controls to escape
from wind shear events.
Figure 6-16: Predictive and Reactive Wind Shear
Appendix H – Low level Wind shear effects on aircraft performances summarizes
the effects of wind shears on aircraft performances.
6.1.3.
WEATHER RADAR OPERATING MODES
According to the weather radar manufacturer, several operating modes are
available. Based on the radar principle, the weather radar is able to detect:
- Weather (or more precisely wet precipitations)
- Turbulence (except Clear Air Turbulence)
- Wind shears
- The ground.
From one manufacturer to another, the operating modes may vary. As a general
rule, the different operating modes are defined for de-cluttering purposes (i.e.
superimposition of different layers of information).
6.1.3.1.
WX MODE
The weather radar detects wet precipitations up to 320 NM and provides a codedcolor display according to their precipitation rates. Refer to 6.1.1.4 – Gain for the
color code.
6.1.3.2.
WX+T, WX/TURB OR TURB MODE
In addition to weather, the weather radar detects and displays turbulence (except
Clear Air Turbulence) in magenta. The detection of turbulence is limited to a
range of 40 NM.
The detection of turbulence (as well as wind shears) is based on the Doppler
principle. Indeed, the weather radar detects an area as turbulent if velocities of
water droplets are above 5 m/s and the area presents high variations in velocities.
The weather radar will not consider an area where water droplet velocities are
quite homogeneous as turbulent.
- 6-13 -
6 – Weather surveillance
Getting to grips with Surveillance
The left part of Figure 6-17 shows a
wide spectrum of velocities but the
numbers of returns for each velocity
are
quite
homogeneous.
The
variation of velocities is smooth.
Figure 6-17: Non turbulent and turbulent
spectra
The right part of Figure 6-17 shows
a
wide
spectrum
with
a
heterogeneous
distribution
of
velocities. The variation of velocities
is irregular and causes turbulence.
The WX+T (Rockwell Collins) or the WX/TURB (Honeywell) combines weather
and turbulence information for display. The TURB mode (Rockwell Collins) only
shows turbulence information for a better identification of turbulent areas.
6.1.3.3.
-
MAP MODE
In addition to weather, the weather radar also displays ground returns. The
colors indicate the various levels of altitude/strength of return of the object
(e.g. water is a good reflector and may appear red). It may permit mainly to
distinguish peaks from valleys in mountainous regions, but with no guarantee
on the quality of the data.
6.1.3.4.
PWS MODE
The Predictive Wind Shear (PWS) supplements the Reactive Wind Shear (refer to
6.1.4 – Reactive Wind Shear. The PWS provides alerts when the aircraft is ahead
of the wind shears for avoidance purposes. The Reactive Wind Shear provides
alerts when the aircraft is in the wind shears for escape purposes.
The PWS detection is based on the Doppler principle. A wind shear is an area
where wind velocities of opposite directions exist on a short distance. The PWS
triggers alerts when wind shears exceed an threshold called Hazard Factor.
6.1.3.4.1.
Hazard Factor F
The Hazard Factor F, developed by NASA, measures the losses of altitude and
airspeed due to wind shears. It is defined as:
F
=
Wh
g
−
V
with
As
Wh: Rate of airspeed loss (kt/s)
G: Gravitational acceleration (19.06 kt/s)
V: Vertical downdraft (kt)
As: Airspeed (kt)
V
Wh
represents the loss of airspeed, and −
the loss of altitude.
g
As
- 6-14 -
Getting to grips with Surveillance
6 – Weather surveillance
The velocity of the vertical down draft V is defined as a negative value. −
then positive. Wind shear alerts are triggered when F > 0.13.
V
is
As
Considering the loss of airspeed only (i.e. V = 0), a variation rate of 2.48 kt/s
would be required to trigger the wind shear alerts.
Considering the loss of altitude only (i.e. Wh = 0), a downdraft of 18.2 kt would
be required to trigger the wind shear alerts, with an airspeed of 140 kt.
6.1.3.4.2.
PWS Automatic Activation
Figure 6-18: Envelopes of Wind Shear alerts
The PWS mode automatically activates when the aircraft is below 2 300 ft RA at
take-off or landing, even if the weather radar is OFF (provided that the PWS
switch is on AUTO). The PWS triggers wind shear alerts below 1 200 ft RA.
To prevent inadvertent alerts, the PWS mode automatically activates if the
following conditions are met:
• Honeywell RDR-4B – Autotilt and Rockwell Collins WXR 701: One
transponder is on AUTO or ON, and one of the engines 2 or 3 is running.
• Rockwell Collins WXR 2100 – Multiscan:
o One of the engines 1 or 2 is running
o One of the following conditions is met:
- The ground speed is above 30 kt, or
- The longitudinal acceleration is above 0.07 g.
For both weather radar models, the controls of TILT and GAIN are automatic in
PWS mode.
- 6-15 -
6 – Weather surveillance
Getting to grips with Surveillance
For both weather radar models, when the PWS detects a wind shear when the
weather radar is OFF (PWS on AUTO), the weather radar automatically switch to:
- WX+T or WX/TURB mode when the ND range is less than 60 NM,
- WX mode when the ND range is more than 60 NM.
When the aircraft passes the wind shear, the weather radar automatically
switches back to OFF.
Note: When one weather radar fails (e.g. WXR 1), the PWS function is not
available until the weather radar switch is set on the second weather radar (e.g.
WXR 2).
6.1.4.
REACTIVE WIND SHEAR
According to the aircraft model, the Reactive Wind Shear is supported by:
- On A300/A310 family aircraft: FAC,
- On A320 family aircraft: FAC,
- On A330/A340 family aircraft: FE part of FMGEC,
- On A340-500/600 aircraft: FE part of FMGEC,
- On A380 aircraft: PRIM.
The Severity Factor (SF) determines the severity of a wind shear.
SF = SFLongitunal + SFVertical with
SFLongitunal for longitudinal tail wind gradient
SFVertical for downward wind.
The Reactive Wind Shear triggers alerts when the estimated SF reaches a
threshold. This threshold depends on the real aircraft energy. The lower the
aircraft energy (or the higher the angle of attack), the lower the threshold for
alerts.
The Reactive Wind Shear alerts are available in high lift configuration between 50
ft and 1300 ft RA.
6.1.5.
WEATHER RADAR FUNCTIONS PER MANUFACTURER
The main manufacturers for weather radar on A320/A330/A340 aircraft are
Honeywell and Rockwell Collins. They use two different philosophies for the
weather detection: the Autotilt for Honeywell and the Multiscan for Rockwell
Collins. The Autotilt and the Multiscan are commonly called the automatic mode
for weather radars.
The following paragraphs describe functions that are specific to weather radar
models, whereas the previous paragraphs were common to both models.
- 6-16 -
Getting to grips with Surveillance
6.1.5.1.
6 – Weather surveillance
AUTOTILT (HONEYWELL)
6.1.5.1.1.
Principle
The Autotilt function of the Honeywell weather radar automatically adjusts the tilt
angle. The Autotilt function takes into account the aircraft altitude and the
terrain information from EGPWS 3 for the tilt angle adjustment.
For Autotilt purposes, the radar scan is divided into five sectors (refer to Figure
6-13). For each sector, the Autotilt function adjusts the tilt angle (beam 2 in
Figure 6-19) according to the terrain altitude from the EGPWS, the aircraft
altitude, and the selected range (i.e. geometric adjustment). When in MAP mode
and the Autotilt is activated, the weather radar points the radar beam to the
ground according to the aircraft altitude and the selected range.
Practically, the Autotilt function prevents errors encountered when the flight crew
manually set the tilt angle. Refer to Figure 6-19.
-
-
Figure 6-19: Optimization of tilt setting
Beam 1 is too high.
Weather and terrain are
over-scanned.
Beam 2 is the optimum
beam determined by the
Autotilt function.
Beam 3 is too low.
Weather and terrain are
under-scanned.
Note: The Honeywell weather radar with the Autotilt function is based on ground
returns. Therefore, the flight crew should pay attention for the interpretation of
heavy rains or ground returns.
6.1.5.1.2.
Autotilt Scan Pattern
•
In weather mode
The Autotilt function operates both in short ranges (less than 80 NM) and in long
ranges (more than 80 NM). Above 2 300 ft:
- If both flight crewmembers set NDs to ranges of the same magnitude
(either short or long ranges), the weather radar updates both ND on
clockwise and counterclockwise scans. With this scan pattern, the
weather radar refreshes the weather display every 4 s.
- If flight crewmembers set NDs to ranges of different magnitude
(short and long ranges), the weather radar alternately scans for
short and long ranges. With this scan pattern, the weather radar
refreshes the weather display every 8 s.
3
Only Honeywell EGPWS is able to provide the terrain altitude to Honeywell Autotilt function. The
Autotilt function is not compatible with ACSS T2CAS.
- 6-17 -
6 – Weather surveillance
Getting to grips with Surveillance
Figure 6-20: Autotilt scans according to range selections
•
In PWS Mode
The Autotilt function does not modify the PWS mode. Below 2 300 ft, the
weather radar alternately scans for weather and wind shear (the first sweep for
weather, the second sweep for wind shear). In PWS mode, the radar scans are
limited to short ranges. With this scan pattern, the weather radar refreshes the
weather display every 12 s.
6.1.5.2.
OPS+
MULTISCAN (ROCKWELL COLLINS)
Principle
6.1.5.2.1.
The
Multiscan
function
develops an ideal radar
beam that would detect
significant weather right
below the aircraft up to
320
NM,
taking
into
account the curvature of
the Earth.
Figure 6-21: Ideal beam and Multiscan
To that end, the Multiscan function uses two radar beams: the upper beam to
scan medium ranges, the lower beam to scan short and long ranges. The
Multiscan function automatically adjusts the tilt and gain settings. The information
from both beam is stored in a database and is cleared of ground returns thanks to
the Ground Clutter Suppression (GCS) function (refer to 6.1.5.3 – Ground
Clutter Suppression – GCS (Rockwell Collins)). According to the range selected on
ND, the relevant information is extracted from the database for display.
- 6-18 -
Getting to grips with Surveillance
6 – Weather surveillance
Figure 6-22: Multiscan processing
6.1.5.2.2.
Multiscan Scan Pattern
•
In weather mode
The weather radar alternatively scans for the
upper beam (e.g. clockwise) and the lower beam
(e.g. counterclockwise). With this scan pattern,
the weather radar refreshes the weather display
every 8 s.
•
In PWS mode
The weather radar alternatively scans for
weather and wind shears, and for the upper
beam and for the lower beam.
illustrates the alternation of weather radar
scans. With this scan pattern, the weather radar
refreshes the weather display every 11.2 s.
6.1.5.3.
Figure 6-23: Multiscan scans
in PWS mode
GROUND CLUTTER SUPPRESSION – GCS (ROCKWELL COLLINS)
The Ground Clutter Suppression function automatically removes ground returns
for display. The GCS function is:
- Available in WX and WX+T modes
- Not active in MAP mode (ground returns are called for display) and
manual operations.
In automatic Multiscan mode, the flight crew may manually and temporarily
deactivate the GCS function at its discretion.
In manual mode, the GCS function is deactivated.
- 6-19 -
6 – Weather surveillance
6.1.5.4.
Getting to grips with Surveillance
LONG RANGE COLOR ENHANCEMENT (ROCKWELL COLLINS)
The Long Range Color Enhancement by Rockwell Collins compensates the beam
attenuation beyond 80 NM. It emulates a red core bordered with yellow and
green for a precipitation that would have appeared fully in green without the color
enhancement. When the aircraft gets closer to the precipitation, the display gets
more accurate.
Radar with Long Range Color
Enhancement
Conventional radar
Figure 6-24: Weather displays with and without Long Range Color Enhancement
6.1.5.5.
GAIN PLUS (ROCKWELL COLLINS)
The GAIN PLUS includes a set of functions available in the automatic Multiscan
mode:
- Conventional increase and decrease of receiver sensitivity,
- Variable temperature based gain,
- Path Attenuation Compensation (PAC) alert,
- Over-flight protection,
- Oceanic weather reflectivity compensation.
6.1.5.5.1.
Conventional Increase and Decrease of Receiver Sensitivity
This function manages the color variation for display when the gain is manually
set. The MAX setting approximately represents an increase of one and half color
level (+16 dB). The MIN setting approximately represents a decrease of one and
half color level (-14 dB).
The CAL setting is the default setting that provides a color code as depicted in
6.1.1.4 – Gain.
- 6-20 -
Getting to grips with Surveillance
6 – Weather surveillance
6.1.5.5.2.
Variable Temperature Based Gain
The reflectivity of water changes according to its state (i.e. liquid or ice). Refer to
6.1.1.1 – Reflectivity of Water Molecules. Therefore, the reflectivity changes
according to the temperature.
-
When the temperature is above 0°C, the gain is constant.
When the temperature is below 0°C, the Variable Temperature Based Gain
function increases the gain to compensate the reflectivity diminution.
When the temperature is below –40°C (water exclusively in ice crystal form),
the Variable Temperature Based Gain function increases the gain by
approximately one color level.
6.1.5.5.3.
OPS+
Path Attenuation Compensation (PAC) alert
When the radar beam is attenuated
(radar shadow, refer to 6.1.1.6.2 –
Attenuation), the Path Attenuation
Compensation (PAC) alert provides a
visual cue on ND: a yellow arc on the
outermost range ring.
The PAC alert is available when the
gain is set to CAL and the attenuation
is within 80 NM.
Figure 6-25: PAC alert
6.1.5.5.4.
Over-Flight Protection
The Over-Flight Protection tracks thunderstorms in the aircraft flight path, and
until the aircraft passes the thunderstorms. The Over-Flight Protection
improves the weather awareness, and may prevent inadvertent penetration
of thunderstorm tops.
With conventional weather radars, the wet part of a thunderstorm (that is the
most visible on radar display) may get below the radar beam when the aircraft
approaches the thunderstorm. Consequently, the thunderstorm may disappear
from the display when the aircraft is getting closer to it.
Thanks to the pair of Multiscan radar beams, the Over-Flight Protection scans
down to 6000 ft below the aircraft to keep the reflective part visible (step 2,
Figure 6-26).
- 6-21 -
6 – Weather surveillance
Getting to grips with Surveillance
When the thunderstorm is
within 15 NM from the
aircraft,
the
Over-Flight
Protection compares the
image of the thunderstorm
stored in the database with
the image of the last scan.
The Over-Flight Protection
displays the image with the
strongest returns.
Figure 6-26: Over-Flight Protection with Multiscan
Therefore, when a threatening thunderstorm gets below the radar beam (i.e.
radar returns are weakening), the image of the thunderstorm stored in the
database is displayed until the aircraft passes the thunderstorm.
The Over-Flight Protection operates above 22 000 ft. The 6000 ft clearance
below the aircraft is a maximum. When the aircraft flies at 26 000 ft, the
clearance is 4 000 ft (26 000 ft minus 22 000 ft).
Similarly, the pair of radar beams
allows the detection of thunderstorm
vault (refer to Appendix G – Aviation
meteorology reminders / G.4.3 –
Thunderstorm Vault) thanks to the
upper beam. Indeed, the most
reflective
part
of
a
vaulted
thunderstorm is the intermediate part
instead the bottom part.
Figure 6-27: Thunderstorm vault
Therefore, as the upper beam scans the intermediate part, the flight crew is able
to correctly evaluate the thunderstorm threat.
6.1.5.5.5.
Regional Weather Reflectivity Compensation
The reflectivity of a cell varies according to the region where the cell develops
(refer to Appendix G – Aviation meteorology reminders / G.2.5 – Oceanic Cell). A
regional weather reflectivity compensation adjusts the gain and tilt for a more
accurate representation of a cell in a given region. The regional weather
reflectivity compensation activates when the aircraft is over a specific type of
region. The weather radar detects the type of the flown region thanks to an
internal data base. The internal data base includes oceanic, equatorial and polar
regions. Based on the aircraft position, the Multiscan radar provides an optimum
tilt adapted to the flown region.
- 6-22 -
Getting to grips with Surveillance
6.1.6.
6 – Weather surveillance
REACTIVE WIND SHEAR INDICATIONS
WIND SHEAR,
WIND SHEAR
WIND
SHEAR,
The red WIND SHEAR indication on PFD
flashes.
Figure 6-28: Reactive Wind Shear
warning on PFD
6.1.7.
WEATHER RADAR INDICATIONS
The weather radar display on ND is available in ROSE and ARC modes.
The weather radar displays weather
information on ND according to the
reflectivity of targets (i.e. green, yellow
or red, refer to 6.1.1.4 – Gain).
Instead of WXR MSG (rounded in dash
red on Figure 6-29), indications from
the weather radar about the operating
modes or failures are displayed.
6.1.7.1 – Weather Radar Messages
provides the list of these indications.
Figure 6-29: Weather display
- 6-23 -
6 – Weather surveillance
Getting to grips with Surveillance
Tips: Specific weather shapes
The shape of a cell provides good cues about its activity:
- A distorted cell indicates turbulence. The distortion of the cell is due to wind
shears inside the cell (Figure 6-30).
- A steep reflectivity gradient (variation of colors on a short distance) indicates
strong convective movements and severe turbulence (Figure 6-31).
- U-shape cells, hooks, fingers, scalloped-edge cell indicate strong wind shears
and turbulence (Figure 6-32 to Figure 6-35).
Shapes that change rapidly also indicate strong activity and turbulence. Intense
and frequent lightning is also a good sign for severe turbulence.
Figure 6-30: Cell
distortion
Figure 6-31: Steep
reflectivity gradient
Figure 6-32: U-shape cell
Figure 6-33: Hook
Figure 6-34: Finger
Figure 6-35: Scalloped
edge
Tips: Use different ranges on NDs
The PF should select a short range on his ND and the PNF should select a long
range. Thanks to this method, the flight crew avoids being trapped by the Blind
Alley effect. The Blind Alley effect is, when the aircraft flies a heading and this
heading reveals a dead-end formed by active cells at a distance greater than the
ND range.
Figure 6-36: Blind Alley effect – Right ND range = 40 NM, Left ND range = 80 NM
- 6-24 -
Getting to grips with Surveillance
WEATHER RADAR MESSAGES
Cause
WXR DU 4
DU overheating
MAN XX.X
Manual tilt
WXR R/T
WXR
transceiver
failure
PRED W/S
W/S failure
WXR ANT
WXR antenna
failure
WXR ATT
Attitude
stabilization
failure
WXR CTL
WXR
control
unit failure
WXR RNG
Discrepancy
between EFIS
CP
range
selection
and
DMC range
MAN GAIN Manual gain
Effect
Image lost
Message
Message
NO AUTOTILT 5
Manual
mode
Cause
Manual
mode
Autotilt failure
WXR STAB
Loss of antenna
stabilization
WXT TEST
Test mode
PWS SCAN 6
Effect
Weather
OFF
Image not lost
6.1.7.1.
6 – Weather surveillance
Test
image
radar
PWS
mode
Note: Shaded cells above apply to Honeywell radar only.
6.1.7.2.
WIND SHEAR INDICATIONS
Predictive Wind Shear Caution
MONITOR RADAR DISPLAY
Predictive Wind Shear Warning
Take-off: WIND SHEAR AHEAD,
WIND SHEAR AHEAD
Landing: GO AROUND, WIND
SHEAR AHEAD
The indications on PFD and ND are almost identical for Caution and Warning,
except W/S AHEAD on PFD appears in red (refer to Figure 6-37 and Figure 6-38).
A yellow sector with red arcs indicates the location of detected wind shears on ND.
In case of a wind shear advisory (refer to Figure 6-18), only the ND indication is
provided (no indication on PFD).
4
This message indicates an overheating of the display unit. It is not a weather radar message.
With EIS1 display units, the message (Honeywell radar only) is displayed in the middle of ND.
6
This message is available with EIS 2 display units only.
5
- 6-25 -
6 – Weather surveillance
Getting to grips with Surveillance
Figure 6-37: Wind shear alert on PFD
Figure 6-38: Wind shear alert on ND
6.1.8.
WEATHER RADAR CONTROLS
The flight crew is able to control four parameters in manual mode:
• The tilt angle: Angle between the beam center and the horizon,
• The gain: The sensitivity of the receiver,
• The ND range,
• The operating mode (WX, WX+T, WX/TURB, TURB, MAP, or PWS; manual or
automatic if available).
Honeywell radar
Rockwell Collins radar
Figure 6-39: Honeywell control panel
with Autotilt function
Figure 6-40: Rockwell Collins control
panel with Multiscan function
Note: The layout and the content of the control panel may change according to
the installed options. Refer to your FCOM for the control panel installed on your
aircraft.
Tips: Use the tilt to measure vertical extensions
To measure the vertical extension of a cell or the vertical distance to the top or
bottom of a cell at a given distance, the following formula can be used:
Height [feet] = Tilt (degrees) x (Distance [NM] + “00”)
- 6-26 -
Getting to grips with Surveillance
When tilting downward
by 1°, the appearance
of a cell at 80 NM
means that the top of
cell is located at 8 000
ft below the aircraft.
Note that in the case of
a
cumulonimbus,
it
indicates the radar top.
6.2.
6 – Weather surveillance
Figure 6-41: Vertical extension measurement with tilt
OPERATIONAL RECOMMENDATIONS FOR WEATHER RADAR
This paragraph of operational recommendations is intentionally non-exhaustive. For
more recommendations, please check your FCOM and/or FCTM as they are more
frequently updated.
Recommendations are also available in pilot’s guides from the weather radar
manufacturers. See References.
6.2.1.
6.2.1.1.
•
•
•
•
•
•
•
FOR THE AIRLINE
Inform your flight and maintenance personnel about radiation hazards
from the weather radar antenna.
Train your flight crews to use the weather radar and to analysis and
interpret weather returns properly and efficiently.
Ensure a proper maintenance of weather radar components including the
radome (e.g. check radome every C check). A faulty component may affect the
sensitivity of the weather radar and then the weather indications on ND.
6.2.1.2.
•
•
WEATHER RADAR OPERATIONS
FOR THE FLIGHT CREW
Periodically scan the weather vertically (tilt) and horizontally (ND range).
Always return to automatic modes (gain and tilt) when the manual
control is no longer necessary. The weather analysis should be done
through a manual control, whereas the weather detection should be left to
automatic modes.
When Autotilt or Multiscan is not available, manually set the tilt so as to have
ground returns at the top of the ND. This setting ensures an optimized
scanning of the weather ahead of the aircraft.
Adjust gain, tilt and ND range to the flight phase. Refer to FOBN quoted
below.
Pay attention when reading weather on ND with Autotilt. Ground returns could
be confused with heavy rains.
Make the decision to avoid a large thunderstorm at least 40 NM away
from the thunderstorm.
- 6-27 -
6 – Weather surveillance
•
•
•
•
•
•
Getting to grips with Surveillance
Avoid cells laterally rather than vertically. Severe turbulence may occur
above the cell (i.e. turbulence dome) and below the cell (i.e. downdraft/updraft
with heavy precipitations).
Avoid thunderstorms on the upwind side. Hazards (hail, gust front, new
cells) develop on the downwind side.
Avoid all cells with green or stronger (including turbulent areas –
magenta) returns by at least 20 NM above FL 230 (10 NM below FL
230). This distance should be increased by 50% if the cell presents a
specific shape (see Figure 6-31 to Figure 6-35). Cumulonimbus should be
cleared by at least 20 NM laterally and 5000 ft vertically.
Pay attention to cells with specific shapes (finger, U-shape, hook,
scalloped edges, etc) or with fast changing shapes. They usually indicate
high turbulence, severe hail or strong vertical drafts.
PNF: Monitor long-range weather (above 80 NM) for long-term
avoidance strategy. PF: Monitor short-range weather (below 80 NM)
for tactical weather avoidance. Refer to Figure 6-36.
Refer to FOBN “Adverse Weather Operations – Optimum Use of the
Weather Radar” (See AIRBUS References) for more recommendations.
6.2.2.
WIND SHEAR
• Refer to FOBN “Adverse Weather Operations – Wind Shear Awareness”
(See AIRBUS References).
6.2.2.1.
•
•
•
Operate the weather radar with PWS. Wind shears were the root cause of
several fatal accidents.
Develop Standard Operating Procedures (SOP) that emphasize
awareness, recognition, avoidance and recovery of wind shears.
Train your flight crews to recognize and avoid wind shears, and to
apply recovery technique. The Wind Shear Training Aid developed by the
industry and other materials about wind shears are available at www.ntis.gov.
6.2.2.2.
•
FOR THE AIRLINE
FOR THE FLIGHT CREW
Report any encountered wind shear to ATC.
Take-off
• Departure briefing: consider most recent weather reports and forecast,
visual observations, and crew experience on airport to build up your wind shear
awareness.
• Consider a delay of the take-off if wind shears are suspected.
• If wind shears are suspected, adapt the aircraft configuration (minimum
required slats/flaps configuration, maximum take-off thrust) to maximize the
climb performances.
• Before the take-off run, check with the weather radar that the flight path is
clear of meteorological hazards.
• Monitor the airspeed and speed trend during the take-off run to detect any
occurrences of wind shear.
- 6-28 -
Getting to grips with Surveillance
•
•
6 – Weather surveillance
In case of wind shear, apply the recovery technique without delay.
Refer to your FCOM.
Refer to FOBN “ Take-off and Departure Operations – Revisiting the
STOP OR GO Decision” (See AIRBUS References).
Descent and approach
• Approach briefing: consider most recent weather reports and forecast, visual
observations, and crew experience on airport to build up your wind shear
awareness.
• Consider a delay of the approach and landing until conditions improve or
divert to a suitable airport when wind shears are reported by other pilots
from other aircraft or by ATC.
• During the approach, check with the weather radar that the flight path is clear
of meteorological hazards.
• Monitor the airspeed and speed trend during the approach to detect any
occurrences of wind shear.
• In case of wind shear, abort the approach and apply the recovery
technique without delay. Refer to your FCOM.
6.3.
REGULATIONS FOR WEATHER RADAR
The interpretation of regulations in this paragraph is limited to AIRBUS aircraft at
the time of writing this brochure.
The carriage of weather radar is recommended in all ICAO member States as per
ICAO Annex 6 – Operation of Aircraft Part I:
“6.11 Recommendation.— Pressurized aeroplanes when carrying passengers
should be equipped with operative weather radar whenever such aeroplanes are
being operated in areas where thunderstorms or other potentially hazardous
weather conditions, regarded as detectable with airborne weather radar, may be
expected to exist along the route either at night or under instrument
meteorological conditions.”
The carriage of forward looking wind shear warning system is recommended in all
ICAO member States as per ICAO Annex 6 – Operation of Aircraft Part I:
“6.21.1 Recommendation.— All turbo-jet aeroplanes of a maximum certificated
take-off mass in excess of 5 700 kg or authorized to carry more than nine
passengers should be equipped with a forward-looking wind shear warning
system.”
Weather radar
• As per EASA EU OPS 1.670: The weather radar is required for pressurized
aircraft operated at night or when IMC apply in areas where potentially
- 6-29 -
6 – Weather surveillance
•
Getting to grips with Surveillance
hazardous weather conditions, detectable by weather radar, may exist
along the route.
As per FAA FAR 121.357: The weather radar is required for any transport
aircraft, except during training, test, or ferry flight, and when the aircraft is
solely operated in areas listed in FAR 121.357 (d) (e.g. Hawaii, Alaska).
Wind Shear
• As per EASA EU OPS 1, no requirement has been found about wind shear
warning and detection.
• As per FAA FAR 121.358: from 02 JAN 91, an approved airborne wind
shear warning and flight guidance system (Reactive Wind Shear),
an approved airborne wind shear detection and avoidance system
(Predictive Wind Shear), or an approved combination of these systems is
required for any aircraft.
Note: Definitions as per AC 25-12
“Airborne Wind Shear Warning and Flight Guidance System: a device or
system which identifies the presence of a severe wind shear phenomena and
provides the pilot with timely warning and adequate flight guidance for the
following:
• Approach/Missed Approach: To permit the aircraft to be flown using
the maximum performance capability available without inadvertent loss
of control, stall, and without ground contact.
• Take-off and Climb-out: To permit the aircraft to be flown during the
initial or subsequent climb segments using the maximum performance
capability available without inadvertent loss of control or ground contact
with excess energy still available.”
“Airborne Wind Shear Detection and Avoidance System: a device or
system which detects a potentially severe wind shear phenomena far enough
in advance of the encounter in both the take-off/climb-out profile and the
approach/landing profile to allow the pilot to successfully avoid the phenomena
and thereby alleviate a flight hazard.”
All AIRBUS aircraft models (except the former aircraft from the
A300/A310 family) are fitted with the Reactive Wind Shear from the
production line. The very first aircraft from the A300/A310 family aircraft is the
A300-B2 certified in 1974. The A310 was certified in 1983 and the A300-600 in
1984. Regulations about wind shear systems appeared in 1991. Consequently,
only the most recent A300/A310 family aircraft are fitted with the Reactive Wind
Shear from the production line.
The Predictive Wind Shear is proposed as an option on all types of weather radar
installed on AIRBUS aircraft.
- 6-30 -
Getting to grips with Surveillance
6.4.
6 – Weather surveillance
MANUFACTURERS FOR WEATHER RADAR
To fulfill the weather awareness function on A300/A310/A320/A330/A340 aircraft,
AIRBUS proposes the following four systems:
• The Honeywell RDR-4B capable of predictive wind shear and Autotilt
• The Rockwell Collins WXR 701X
• The Rockwell Collins WXR 2100 capable of predictive wind shear and
Multiscan.
Figure 6-42 provides a simplified view of the weather radar architecture.
WXR
Antenna
Radio
Radio
Altimeter
Altimeter
ADIRU
Weather
WeatherRadar
Radar
Transceiver
Transceiver
TAWS*
ACAS
Weather Radar
Control Panel
Figure 6-42: Weather Radar architecture
* Link TAWS to WXR only applicable between Honeywell EGPWS to Honeywell
weather radar capable of Autotilt.
6.4.1.
HONEYWELL RDR-4B
From Honeywell, the RDR-4B capable of PWS and Autotilt is available on AIRBUS
aircraft. The Autotilt function is optional.
More information is available at
http://www.honeywell.com/sites/aero/Radar3_C867EC130-221E-7DEE-00E19B9088CBF060_H5CBA7513-E2B2-3320-D5A0-AF32226E4F40.htm
6.4.2.
ROCKWELL COLLINS WXR 701X AND WXR 2100
From Rockwell Collins, the WXR 701X capable of PWS and the WXR 2100 capable
of PWS and Multiscan are available on AIRBUS aircraft.
More information is available at
http://www.rockwellcollins.com/products/cs/at/avionics-systems/weatherhazard/index.html
- 6-31 -
6 – Weather surveillance
6.5.
Getting to grips with Surveillance
FUTURE SYSTEMS
6.5.1.
HONEYWELL RDR 4000
The Honeywell RDR 4000 uses the buffering of weather data in a 3D data base
thanks to a multiple scanning. The RDR 4000 supports the weather radar function
in the A380 AESS (refer to 7.1.4 – Weather Radar Function). Honeywell and
AIRBUS are studying the opportunity to install the RDR 4000 on A320 family
aircraft for early 2010 and on A330/A340 aircraft for end 2010. The RDR 4000
builds the weather display based on the 3D data base. This method improves the
weather awareness and the workload of the flight crew. The RDR 4000 on
A320/A330/A340 aircraft will propose new features (refer to 7.1.4 – Weather
Radar Function for details):
- The automatic correction of the Earth curvature,
- Automatic modes to display on-path and off-path weather,
- The elevation mode: extraction of weather information via a horizontal cut
across the 3D buffer.
- 6-32 -
Getting to grips with Surveillance
6 – Weather surveillance
Please bear in mind…
Description
Operating in the X-band frequency (9.3 GHz), the weather radar detects any wet
meteorological phenomena (clouds, precipitations, turbulence). Therefore, Clear
Air Turbulence are not detected, and a weak reflectivity does not necessarily
mean that the area is safe (e.g. dry hail).
For A300/A310/A320/A330/A340 aircraft, weather radars from two manufacturers
are available: Honeywell (RDR-4B) and Rockwell Collins (WXR701X/2100).
The automatic function (Autotilt for RDR-4B or Multiscan for WXR 2100) is
optional.
Operational recommendations
The main recommendations (but non exhaustive) are:
• An appropriate maintenance of all weather radar components including the
radome
• An appropriate and recurrent training on weather radar
• A sharp knowledge on how to interpret weather radar indications
• An anticipation of the weather ahead the aircraft (take-off, cruise,
approach)
• Use automatic mode per default
• Use of manual mode for analysis purposes.
• A good preparation to abort a procedure (take-off or approach) in
case of wind shear
• Do not fly into a thunderstorm. Avoid flying above or below a
thunderstorm.
Refer to 6.2 – Operational Recommendations for Weather Radar.
Regulations
The carriage of a weather radar is recommended as per ICAO Annex 6 –
Operation of Aircraft – Part I. In most countries, the weather radar is required
considering that significant weather may be experienced in most flights. Refer to
local regulations.
Future systems
The Honeywell RDR 4000, already available on A380 aircraft, will introduce the
benefits of the 3D weather scanning on A320/A330/A340 aircraft in 2010 such as:
• The automatic correction of the Earth curvature
• Automatic modes to display on-path and off-path weather
• The elevation mode.
- 6-33 -
Getting to grips with Surveillance
7 – Aircraft environment surveillance
7. AIRCRAFT ENVIRONMENT SURVEILLANCE
7.1
7.1.1
7.1.2
7.1.2.1
7.1.2.2
7.1.2.3
7.1.3
7.1.3.1
7.1.3.2
7.1.3.3
7.1.4
7.1.4.1
7.1.4.2
7.1.4.3
7.1.4.4
7.1.5
7.1.6
7.1.7
7.1.7.1
7.1.7.2
7.1.8
7.1.8.1
7.1.8.2
7.1.9
7.1.9.1
7.1.9.2
7.1.9.4
7.1.9.5
7.2
7.2.1
7.2.1.1
7.2.1.2
7.2.1.3
Description of AESS
Integration of Surveillance Functions
AESS Architecture
Groups of Functions
AESS Operating Modes
AESS Reconfiguration Principles
TAWS Function
TAWS RNP
Selection of Lateral Position Source
Terrain Display in Polar Areas
Weather Radar Function
Weather Detection
Enhanced Turbulence Detection
Predictive Wind Shear (PWS) Detection
Ground Mapping
TCAS Function
Transponder Function
Vertical Display
Generation of Vertical Terrain View
Generation of Vertical Weather View
AESS Indications
Navigation Display (ND)
Vertical Display (VD)
AESS Controls
KCCU SURV Key
EFIS Control Panel (EFIS CP)
SURV Pages on MFD
SQWK Page on RMP
Operational Recommendations for AESS
For the Airline
Transponder Function
TCAS Function
TAWS Function
- 7-1 -
7-3
7-3
7-4
7-5
7-5
7-6
7-7
7-7
7-8
7-8
7-9
7-9
7-15
7-15
7-16
7-16
7-16
7-16
7-18
7-19
7-21
7-21
7-22
7-24
7-25
7-25
7-25
7-27
7-27
7-27
7-27
7-27
7-27
7 – Aircraft environment surveillance
7.2.1.4
7.2.2
7.2.2.1
7.2.2.2
7.2.2.3
7.2.2.4
7.3
7.3.1
7.3.2
7.3.3
7.3.4
7.4
7.5
7.5.1
Getting to grips with Surveillance
Weather Radar Function
For the Flight Crew
Transponder Function
TCAS Function
TAWS Function
Weather Radar Function
Regulations for AESS
Transponder Function
TCAS Function
TAWS Function
Weather Radar Function
Manufacturers for AESS
Future Systems
Airborne Traffic Situational Awareness (ATSAW)
- 7-2 -
7-28
7-28
7-28
7-28
7-28
7-28
7-28
7-29
7-29
7-29
7-29
7-29
7-29
7-29
Getting to grips with Surveillance
7.1.
7 – Aircraft environment surveillance
DESCRIPTION OF AESS
7.1.1.
INTEGRATION OF SURVEILLANCE FUNCTIONS
The Aircraft Environment Surveillance System (AESS) is an integrated
system that ensures the surveillance function on-board the A380 aircraft. AESS
includes:
The Aircraft Identification and Position Reporting function: Transponder
The Traffic Surveillance function: TCAS II
The Terrain Surveillance function: TAWS
The Weather Surveillance function: Weather radar with PWS capability.
The Runway Surveillance function is outside the AESS scope and is supported by
the OANS (refer to 5.1 – Description of OANS).
The integration of these functions removes some drawbacks brought by individual
surveillance systems. Indeed, the well-known surveillance systems had been
defined to cope with one single issue and had appeared all along the aviation
history: the weather radar in 1970’s, the GPWS in 1974, the TCAS in 1990’s and
the PWS in 1994.
The drawbacks of a cumulative architecture, resulting from the history of
surveillance functions, are:
- Limited management of alert priority,
- Poor interactivity between functions,
- Multiplication of control panels,
- Heterogeneous alerts from various manufacturers,
- Complex management of spares of different systems from various
manufacturers,
- Complex installation (wiring, antennas),
- Weight, size, consumption, and maintenance tasks multiplied by the
number of systems,
- High global cost.
From an operational perspective, AESS optimizes the layout of controls and
displays in the cockpit:
- EFIS CP: Controls of display
- ND: Display of surveillance information
- PFD: Display of alerts
- ECAM: Display of failures or memo
- SURV panel on pedestal: Quick access to controls of main surveillance
functions
- MFD SURV page: Access to all surveillance functions (settings, status, and
reconfiguration).
- 7-3 -
7 – Aircraft environment surveillance
Getting to grips with Surveillance
7.1.2.
AESS ARCHITECTURE
The AESS includes:
• Two Aircraft Environment Surveillance Units (AESU),
• Two Radar Transceiver Units (RTU) that makes the interface between
AESU and the weather radar antenna,
• One Weather Antenna Drive Unit (WADU) that ensures the scanning
movement of the weather radar antenna and its stabilization,
• One weather radar flat antenna,
• One SURV panel,
• Four identical TCAS/Mode S antennas.
Each AESU includes three modules:
• TCAS/XPDR module: A single module contains the TCAS and XPDR
functions to take benefits from a higher integration: smaller size, lower
consumption, simpler design, shared TCAS/XPDR antennas,
• TAWS module is roughly equivalent to EGPWS,
• WXR/PWS module ensures the basic functions (detection of weather,
wind shears, turbulence, ground mapping) and introduces a new feature
(3D buffer).
WXR
Antenna
WADU
RTU
RTU
AFDX
AFDX
RMP
AESU
AESU
TCAS/ModeS
TCAS/ModeS
TCAS/Mode
SS
TCAS/Mode
Antennas
Antennas
Antennas
Antennas
FCU
FCU
AESS
Control Panel
Figure 7-1: Simplified AESS architecture
For any module, each AESU records various parameters for any events that occur
during the flight (e.g. TCAS parameters relative to an RA).
- 7-4 -
Getting to grips with Surveillance
7.1.2.1.
7 – Aircraft environment surveillance
GROUPS OF FUNCTIONS
The integration highly simplifies the architecture. However, it introduces some
new rules in terms of operations. The architecture with two AESUs duplicates each
surveillance function.
AESU1
AESU2
WXR
TAWS
WXR
TAWS
XPDR
TCAS
XPDR
TCAS
Each AESU groups the functions as
follows:
- WXR/TAWS,
- TCAS/XPDR.
Figure 7-2: AESU groups of functions
7.1.2.2.
AESS OPERATING MODES
AESS presents three different operating modes:
1. Normal mode: one AESU performs all functions. It is the Master AESU. The
Master AESU is the AESU with the active WXR/TAWS group,
2. Mixed mode: one AESU performs the functions of one group, and the other
AESU performs the functions of the other group, with or without failure (e.g.
WXR/TAWS on AESU1 and TCAS/XPDR on AESU2),
3. Downgraded mode: a failure prevents the performance of all functions
despite the redundancy of functions. Refer to examples below.
In the examples below, active functions are framed in green and failed
functions are shaded in amber.
AESU1
AESU2
AESU1
AESU2
WXR
TAWS
WXR
TAWS
WXR
TAWS
WXR
TAWS
XPDR
TCAS
XPDR
TCAS
XPDR
TCAS
XPDR
TCAS
Figure 7-3: Normal mode
Figure 7-4: Mixed mode
- 7-5 -
7 – Aircraft environment surveillance
Getting to grips with Surveillance
AESU1
AESU2
AESU1
AESU2
WXR
TAWS
WXR
TAWS
WXR
TAWS
WXR
TAWS
XPDR
TCAS
XPDR
TCAS
XPDR
TCAS
XPDR
TCAS
Figure 7-5: Downgraded mode – Loss
of WXR
Figure 7-6: Downgraded mode – TAWS
alerts remain available via an
interconnection with TAWS 2
Note: In normal mode, when the aircraft is on ground, the master AESU is:
- When an odd flight number is entered (e.g. AIB123), AESU1.
- When an even flight number is entered (e.g. AIB234), AESU2.
7.1.2.3.
AESS RECONFIGURATION PRINCIPLES
Two successive faults lead the AESS to operate in downgraded mode. A fault is a
loss of a function (e.g. WXR1) or a loss of a group of functions (e.g. WXR/TAWS of
AESU2).
Note 1: The TCAS automatically switches to STBY when the XPDR is in STBY or
when the ALT RPTG is OFF. Indeed, the TCAS is not able to determine the vertical
separation with the intruder. Therefore, the TCAS is not able to evaluate the
threat. Refer to 3.1.4 – Collision Threat Evaluation.
Note 2: The TAWS function of one AESU is able to feed the other AESU for TAWS
alert generation, when the TAWS function of the other AESU is faulty. Refer to
Figure 7-9.
AESU1
AESU2
WXR
TAWS
WXR
TAWS
XPDR
TCAS
XPDR
TCAS
Figure 7-7 to Figure 7-9 illustrate a
sequence of events that leads to
reconfiguration
in
downgraded
mode.
Figure 7-7:
normally.
Figure 7-7: AESS in normal mode
- 7-6 -
The
AESS
operates
Getting to grips with Surveillance
7 – Aircraft environment surveillance
AESU1
AESU2
WXR
TAWS
WXR
TAWS
XPDR
TCAS
XPDR
TCAS
Figure 7-8: The first failure is the loss
of WXR function of AESU1. Per
procedure, the WXR/TAWS function is
switched to AESU2.
Figure 7-8: AESS in mixed mode
AESU1
AESU2
WXR
TAWS
WXR
TAWS
XPDR
TCAS
XPDR
TCAS
Figure 7-9: The second failure is the
loss of TAWS function of AESU2. As the
TAWS function of AESU1 is still
available, TAWS alerts remain available
thanks to an interconnection between
TAWS functions of AESU1 and 2.
Figure 7-9: AESS in downgraded mode
Refer to your FCOM for more reconfiguration scenarios.
7.1.3.
TAWS FUNCTION
The AESS TAWS function is equivalent to the reactive and predictive functions
provided by the EGPWS (refer to 4.1 – Description of TAWS, see reactive modes,
TCF, RFCF, TAD, envelope modulation, obstacle, peaks mode).
In addition to the EGPWS set of functions, the AESS TAWS function provides an
enlarged ND range (up to 640 NM) and a vertical view of the terrain on VD.
7.1.3.1.
TAWS RNP
The TAWS RNP is defined according to the flight phase.
Flight phase
Take-off
Conditions
Below 4000
ft AGL and
GS > 60kt
TAWS RNP (NM)
1
Terminal
En-route
Approach
Below 3500
Below 16000
Outside
ft and 10 NM
ft and 50 NM
other phases
from runway
from runway
1
2
0.5 or less*
* According to the runway selected into the FMS.
AESS uses the TAWS RNP to select the position source (GPIRS or FMS), and to
define the width of the vertical cuts for vertical terrain view (refer to 7.1.7.1 –
Generation of Vertical Terrain View).
- 7-7 -
7 – Aircraft environment surveillance
7.1.3.2.
Getting to grips with Surveillance
SELECTION OF LATERAL POSITION SOURCE
The TAWS module selects the position source with the highest accuracy and
integrity in the following sequence (by order of priority):
1. GPS position, then
2. GPS-corrected IR data, then
3. FMS position, then
4. IR position.
When all these sources are not valid or not accurate enough:
- If the automatic deactivation of predictive TAWS functions has been selected
(pin-programming), AESS automatically deactivates predictive functions (basic
TAWS functions remain active).
- If the automatic deactivation of predictive TAWS functions has not been
selected, the flight crew must manually switch predictive functions to OFF (TERR
SYS to OFF on MFD SURV page, refer to 7.1.9.4.1 – CONTROLS Page).
7.1.3.3.
TERRAIN DISPLAY IN POLAR AREAS
The terrain database is coded in
latitudes/longitudes
(spherical
coordinates). The displays (ND and VD)
are
graduated
in
NM
(plane
coordinates).
The
TAWS
function
translates the latitudes/longitudes into
distances (i.e. projection of a spherical
image on a plan). Consequently, this
translation implies two limitations for
the display of terrain.
Figure 7-10: World map with
interrupted Goode’s projection
Figure 7-10 illustrates discontinuities when translating a spherical world map into
a plane world map. The interrupted Goode’s projection shows areas near the Poles
with minimal distortion.
•
Black Bands: Incomplete Terrain Coverage
For low latitudes, the terrain information extracted from the terrain database
(spherical coordinates) is adapted to the current latitude for display (plane
coordinates) with small distortions.
Near 84° of latitude, the convergence of meridians implies some significant
distortions when latitudes/longitudes are translated into distances. In other
words, the terrain information cannot be adapted to the current latitude without
visible discontinuities. These discontinuities appear as black bands on ND (the
amber TERR INOP indication is displayed on VD). When the aircraft gets closer to
the North or South Pole, the discontinuities (i.e. black bands) get larger.
- 7-8 -
Getting to grips with Surveillance
7 – Aircraft environment surveillance
•
Magenta Areas: Unavailable
Terrain Information
The latitude range is - 90° to + 90°.
When the aircraft flies to the North
Pole, the latitude increases to 90°.
When the aircraft passes the North
Pole, the latitude decreases from 90°
(vice versa across the South Pole).
From a mathematical point of view, the
latitude should increase when the
aircraft flies to and passes the North
Pole (i.e. …88°, 89°, 90°, 91°, 92°…).
Due to the limits of the latitude range,
the TAWS function considers there is no
terrain information beyond 90° of
latitude. The TAWS function displays
the corresponding areas in magenta on
ND (the amber TERR INOP indication is
displayed on VD).
Figure 7-11: Terrain display in polar
areas
Note: EGPWS is also affected by these limitations. Refer to 4.1.5.5 – Terrain
Display in Polar Areas.
7.1.4.
WEATHER RADAR FUNCTION
The AESS Weather Radar function provides the same functions as conventional
weather radars: weather detection with PWS and turbulence detection. The
range goes up to 320 NM. The antenna scans an envelope of +/- 80° in azimuth
and +/- 15° in tilt. Refer to Figure 7-24.
The AESS Weather Radar function introduces a new concept: the weather radar
does not directly display the weather information to the flight crew, but
stores it in a 3D buffer. The 3D buffer significantly improves the weather
analysis (i.e. on/off path weather, elevation mode, vertical view, Earth curvature
correction, automatic ground mapping, weather displayed behind the aircraft) and
the weather awareness.
Note: The weather radar basic principles remain identical to the ones described in
6 – Weather Surveillance –. Refer to this chapter for a refresher about weather
radar physics.
7.1.4.1.
WEATHER DETECTION
With weather returns stored in a 3D buffer, the AESS Weather Radar function
provides different operating modes (automatic and manual). The following
paragraphs describe the 3D buffer principles, and the automatic and manual
operating modes.
- 7-9 -
OPS+
7 – Aircraft environment surveillance
Getting to grips with Surveillance
7.1.4.1.1.
3D Buffer
Conventional radars directly update the weather display according to the radar
antenna position. The AESS radar antenna continuously scans the envelope ahead
of the aircraft and stores weather returns in a 3D buffer. Then, the AESS uses
weather information stored in the 3D buffer for display on ND and VD. With the
3D buffer, the weather display is no more correlated with the radar antenna
position.
At the first activation of the weather radar (e.g. on runway before take-off or when
switching from SYS 1 to SYS 2), a minimum scanning is required to fill the 3D
buffer in. It takes up to 30 seconds to get a full weather picture on VD and ND.
Figure 7-12: AESS 3D buffer
•
Earth Curvature Correction
AESS applies a correction of the Earth curvature on weather information extracted
from the 3D buffer. The effects of the Earth curvature are noticeable beyond 40
NM.
Note: A straight beam over a curved ground surface is equivalent to a curved
beam over a plan ground surface. Refer to Figure 7-13.
- 7-10 -
Getting to grips with Surveillance
7 – Aircraft environment surveillance
Figure 7-13: Effect of Earth curvature
The following figures illustrate the AESS corrections.
Figure 7-14: AESS correction of Earth curvature for tilt and elevation
7.1.4.1.2.
Automatic Mode – WXR AUTO
In automatic mode, the AESS Weather Radar displays the weather information
according to the active navigation mode:
- STANDARD WXR AUTO based on FMS flight plan path and FCU
altitude when the navigation mode is managed (refer to Figure
7-15),
- BASIC WXR AUTO based on flight path along FPA up to FCU altitude
when the navigation mode is selected (refer to Figure 7-16),
- DEFAULT WXR AUTO based on flight path along FPA up to 60 NM
when the navigation mode is manual (refer to Figure 7-17).
•
The On-Path and Off-Path Weather Concept
An envelope is defined along the current flight path. The envelope expands
4000 ft above and below the flight path. In addition, the lower boundary is 25 000
ft at most, and the higher boundary is 10 000 ft at least.
OPS+
-
The on path weather is the weather inside this envelope,
The off path weather is the weather outside this envelope.
- 7-11 -
7 – Aircraft environment surveillance
Getting to grips with Surveillance
The STANDARD WXR AUTO mode is
active when:
- The flight crew sets WXR AUTO on
the SURV panel or on the MFD SURV
CONTROLS page
- The FMS flight plan is available
Figure 7-15: STANDARD WXR AUTO envelope
The BASIC WXR AUTO mode is active when:
- The flight crew sets WXR AUTO on the SURV panel or on the MFD SURV
CONTROLS page
- The navigation mode is selected
- The aircraft is converging to the selected FCU altitude.
Figure 7-16: BASIC WXR AUTO
envelope in climb
Figure 7-17: BASIC WXR AUTO
envelope in descent
The DEFAULT WXR AUTO mode is active when:
- The flight crew sets WXR AUTO on the SURV panel or on the MFD SURV
CONTROLS page
- The FMS flight plan is not available
- No FCU altitude is selected.
Figure 7-18: DEFAULT WXR AUTO
envelope in climb
Figure 7-19: DEFAULT WXR AUTO
envelope in descent
•
Generation of Horizontal Weather View
AESS uses the On-path and Off-path weather concept to generate the horizontal
weather view on ND. The AESS displays On-path weathers with solid colors
and Off-path weathers with dashed colors.
- 7-12 -
Getting to grips with Surveillance
7 – Aircraft environment surveillance
Figure 7-20: Generation of weather view on ND
Step 1:
Refer to Figure 7-20.
AESS draws the envelope of the On-path weather on the current
aircraft flight path (see above).
Step 2:
AESS rotates the On-path weather envelope around a vertical axis to
form a 3D envelope.
Step 3:
This 3D envelope defines a set of vertical laser cuts 1 in the 3D buffer.
1
The thickness of the laser cut is nil. Refer to 7.1.7.2 – Generation of Vertical Weather View.
- 7-13 -
7 – Aircraft environment surveillance
Getting to grips with Surveillance
Step 4:
For each vertical laser cut, AESS projects the On-Path weather of the
highest reflectivity on the horizontal plane. If there is no On-Path
weather, AESS projects the Off-Path weather of the highest reflectivity
on that horizontal plane.
Step 5:
Finally, the projections of vertical laser cuts on the horizontal plane
form the horizontal weather view.
7.1.4.1.3.
Manual Modes
The 3D buffer eases the manual weather analysis with an enhanced tilt mode, a
new elevation mode, and a new azimuth mode.
•
Tilt Mode
The enhancement of the tilt mode is triple:
- AESS applies a correction of the
Earth curvature on the tilt angle.
- In tilt mode, AESS makes a 360°
laser cut around the aircraft
along the tilt angle across the 3D
buffer. In ND ROSE mode, the
OPS+
AESS
displays
the
weather
behind the aircraft.
- The
ground
de-cluttering
is
automatic. Thanks to the terrain
Figure 7-21: Tilt mode
database, AESS removes terrain
returns from the weather image (refer to 7.1.4.4 – Ground Mapping). In
addition, beyond the intersection of the laser cut and the ground, the weather
is not displayed. Refer to Figure 7-22.
Figure 7-22: Inhibition of weather display beyond the laser cut
- 7-14 -
Getting to grips with Surveillance
7 – Aircraft environment surveillance
•
Elevation Mode
In elevation mode, AESS:
- Makes a 360° horizontal laser cut
at the selected altitude across the 3D
buffer
- Displays the weather behind the
aircraft in ND ROSE mode.
OPS+
The selectable altitude range goes from
the ground level to 60 000 ft or
FL600.
Figure 7-23: Elevation mode
•
Azimuth Mode
In azimuth mode, AESS:
- Makes a vertical laser cut at the selected azimuth across the 3D buffer
- Displays the weather contained in the vertical laser cut on VD.
Refer to 7.1.7.2 – Generation of Vertical Weather View and Figure 7-33.
7.1.4.2.
ENHANCED TURBULENCE DETECTION
The turbulence detection has
been improved thanks to new
pulse waveforms and digital
signal
processing.
The
detection range is 40 NM
from the aircraft and 20 NM
laterally on either side from
the aircraft centerline.
When the AESS detects
the
AESS
turbulence 2,
displays turbulence on ND in
all weather radar operating
modes
including
ground
Figure 7-24: AESS radar coverage
mapping.
The AESS does not display turbulence on the Vertical Display.
7.1.4.3.
PREDICTIVE WIND SHEAR (PWS) DETECTION
The AESS automatically activates the PWS detection below 1 500 ft AGL. The
detection range goes from 0.5 to 5 NM. When the AESS detects wind shears, the
AESS displays wind shears on ND in all weather radar operating modes including
ground mapping. Wind shears are not shown on Vertical Display.
Refer to Figure 6-18 for the envelopes of wind shear alerts (Honeywell pattern).
2
As a reminder, the weather radar does not detect Clear Air Turbulences (CAT).
- 7-15 -
7 – Aircraft environment surveillance
7.1.4.4.
Getting to grips with Surveillance
GROUND MAPPING
OPS+
The AESS automatically generates the Ground Mapping view without any action
from the flight crew (i.e. no tilt and gain settings required). A Ground Clutter
Suppression continuously runs on data from the weather antenna. To identify
ground returns, the Ground Clutter Suppression compares radar returns with the
terrain and obstacle databases of the TAWS function. The AESS separates weather
and ground returns in the 3D buffer to provide a weather image and a ground
image.
Note: if terrain/obstacle elevation from the TAWS database is not valid, the
Ground Clutter Suppression does not work properly. The weather image may
contain ground returns, and the ground image may contain weather returns.
7.1.5.
TCAS FUNCTION
The TCAS function of the AESS is compliant with TCAS II Change 7.0. The collision
avoidance principle is not changed. For more details, refer to 3 – Traffic
Surveillance.
7.1.6.
TRANSPONDER FUNCTION
The transponder function of the AESS is able to:
- Reply to Mode A and C interrogations,
- Operate in Mode S environments (ELS and EHS),
- Operate with the TCAS function,
- Broadcast ADS-B messages (compliant with DO-260A 3).
Refer to 2 – Aircraft identification and position reporting for more details on
transponder principles.
7.1.7.
VERTICAL DISPLAY
The Vertical Display (VD) is one of the novelties introduced by the A380 cockpit. It
provides the vertical view of:
- Safety altitudes,
- Weather information, and
- Predicted trajectory,
- Terrain information.
The description of VD in this paragraph focuses on weather and terrain
information. For more details, refer to your FCOM.
VD displays the aircraft symbol, the vertical flight plan, and horizontal and vertical
scales. VD displays weather and terrain information as a background
image. The horizontal scale equals the selected ND range up to 160 NM that is
the maximum horizontal VD range (e.g. the horizontal VD range remains at 160
NM even if the ND range is greater than 160 NM in ARC mode). VD adapts the
vertical scale to the horizontal scale in order to fit to the VD window.
The VD background image runs along the lateral flight path defined by the active
navigation mode or a manually selected azimuth.
3
The transponder function of the A380 AESS is compliant with DO-260A including the geographic
filtering of Mode A code (refer to 2.2.7 – Geographical Filtering of SQWK Code).
- 7-16 -
Getting to grips with Surveillance
7 – Aircraft environment surveillance
•
VD Background Image on the lateral flight path defined by the
active navigation mode
The VD background image runs along:
- The FMS flight plan when the navigation mode is managed, or
- The XLS approach course, or
- The current track when:
The navigation mode is managed and the aircraft significantly deviates
from the FMS flight plan (see below) or from the XLS approach course,
or
The navigation mode is selected (HDG or TRK).
When the VD background image is along the FMS flight plan, a vertical cut
is made for each leg. The VD image along the FMS flight plan is a concatenation of
all these vertical cuts.
When the VD background image is
along the FMS flight plan, a vertical
cut is made for each leg. The VD image
along the FMS flight plan is a
concatenation of all these vertical cuts.
When the aircraft significantly
deviates from the FMS flight plan,
the VD image returns on aircraft track.
The VD switches between “on
track” mode and “on FMS flight
plan path” mode with a threshold of
1 RNP approximately. For instance,
when RNP is 1 NM, the switch occurs at
1 NM from the FMS flight plan leg. Refer
to Figure 7-25.
Figure 7-25: VD path reference
If the track changes by more than
3° after the TO waypoint, the vertical
view after the TO waypoint is shaded in
grey. Refer to Figure 7-26.
Figure 7-26: Track change and absence
of terrain information on VD
When the terrain information is not
available, the corresponding portion of
the vertical view is shaded in magenta.
•
VD Background Image on Manually Selected Azimuth
The VD background image runs along an azimuth selected by a flight crewmember
(refer to 7.1.9.3 – SURV Panel). The azimuths selected by the Captain and the
First Officer for the VD image are independent. The azimuth range is +/- 60° from
the current track with increments of 1°.
- 7-17 -
7 – Aircraft environment surveillance
7.1.7.1.
Getting to grips with Surveillance
GENERATION OF VERTICAL TERRAIN VIEW
According to the VD path reference (aircraft track, FMS flight plan, or manual
azimuth), the TAWS function makes a vertical cut along the VD path reference in
the terrain database.
Figure 7-27: Generation of vertical terrain view along FMS flight plan path
Figure 7-29: Generation of vertical
terrain view along azimuth
Figure 7-28: Generation of vertical
terrain view along track
The width of the vertical cut depends on the VD path reference.
- VD image on FMS flight plan path:
For the active leg: 2x FMS RNP
or 2x FMS EPU, whichever is
the greater,
2x
For
subsequent
legs:
predicted RNP,
- VD image on aircraft track:
2x TAWS RNP,
- VD image on manually selected azimuth: 2x TAWS RNP.
- 7-18 -
Getting to grips with Surveillance
7 – Aircraft environment surveillance
Note: The RNP value is adapted to the flight phase. Therefore, the corridor width
is variable along the flight path.
The terrain database is divided into grids sets (refer to 4.1.1.1 – Terrain
Database). The vertical cut in the terrain database determines a group of grid set
elements. The TAWS function retains the highest elements along the VD path
reference to build up the terrain elevation profile. Refer to Figure 7-30.
Figure 7-30: Cut through terrain database
The TAWS function always displays the terrain on VD in brown, regardless of the
proximity of terrain or obstacles. The TAWS function displays water on VD in cyan
as on ND.
7.1.7.2.
GENERATION OF VERTICAL WEATHER VIEW
The same principle applies for the generation of vertical weather view. The WXR
function makes a vertical cut in the 3D buffer along the VD path reference
(aircraft track, FMS flight plan or manual azimuth). However, the vertical cut in
the weather radar 3D buffer has no width. It is a “laser cut”.
• Image generation in automatic modes
Figure 7-31: Generation of vertical weather view along FMS flight plan
- 7-19 -
7 – Aircraft environment surveillance
Getting to grips with Surveillance
Figure 7-32: Generation of vertical
weather view along track
Figure 7-33: Generation of vertical
weather view along azimuth
•
Image generation in manual modes
In tilt and elevation modes, the WXR function makes the laser cut as illustrated in
7.1.4.1.3 – Manual Modes.
7.1.7.3.
INTERPRETATION OF WEATHER AND TERRAIN ELEVATION ON VD
The aircraft altitude on VD is the barometric altitude. Atmospheric conditions
(temperature and pressure) influence the barometric altitude. As a consequence:
- At the current aircraft position (i.e. where atmospheric conditions are known),
terrain and weather elevation are reliable on VD.
- Ahead of the current aircraft position (i.e. where atmospheric conditions are
unknown), terrain and weather elevations are not reliable on VD.
Figure 7-34 illustrates the case where the air ahead of the aircraft is getting
colder. The aircraft is at 5 000 ft. The 5 000 ft isobar gets lower as the air
temperature decreases. The terrain elevation below the aircraft is 2 000 ft (mark
1 in Figure 7-34) as atmospheric conditions are known. However, the highest
terrain elevation ahead of the aircraft is not 3 000 ft as AESS does not know the
atmospheric conditions at that location (mark 2 in Figure 7-34).
The same interpretation can be made for weather information.
Do not directly read weather and terrain elevations on VD as they depend on local
atmospheric conditions.
- 7-20 -
Getting to grips with Surveillance
7 – Aircraft environment surveillance
Figure 7-34 – Interpretation of weather and terrain information on VD
7.1.8.
7.1.8.1.
AESS INDICATIONS
NAVIGATION DISPLAY (ND)
Captain and First Officer ND displays are independent. Each flight crewmember
can display the desired information (terrain or weather) in the desired mode (tilt,
elevation, azimuth, or automatic).
Figure 7-36: A380 ND WXR view
Figure 7-35: A380 ND TAWS view
AESS displays turbulence indications on ND within:
- 40 NM ahead of the aircraft
- 20 NM on either side of the aircraft centerline
- 4 000 ft above or below the aircraft altitude.
Refer to Figure 7-24 for AESS radar coverage.
- 7-21 -
7 – Aircraft environment surveillance
Getting to grips with Surveillance
Figure 7-37: Wind shear icons for ND
range of 10 NM
Figure 7-38: Wind shear icons for ND
range greater than 10 NM
To enhance awareness of wind shears, the WXR function highlights sectors where
wind shears occur in yellow for ND range greater than 10 NM.
7.1.8.2.
VERTICAL DISPLAY (VD)
•
VD image on aircraft track
When the VD image is on aircraft track
and the aircraft is under specific
conditions 4, the white indication VIEW
ALONG ACFT TRK is displayed at the
bottom of VD.
Figure 7-39: VD image on aircraft track
•
VD image on FMS flight plan
path
Figure 7-40: VD image on FMS flight
plan path
•
VD
image
on
manually
selected azimuth
When the VD image is on manually
selected azimuth, the cyan indication
VIEW ALONG AZIM NNN° (NNN is the
manually selected azimuth) is displayed
at the bottom of VD. The eye icon
highlights the manual setting.
4
Figure 7-41: VD image on manual
selected azimuth
For instance, in managed mode, when the aircraft deviates from the flight plan or the XLS approach
course. Refer to your FCOM for details.
- 7-22 -
Getting to grips with Surveillance
7 – Aircraft environment surveillance
The AESS also displays a white reference line on ND to illustrate the manually
selected azimuth (refer to Figure 7-36).
When the flight crew does not select any new azimuth value during 30
seconds, the VD image automatically returns to a default VD path
reference (i.e. along aircraft track or FMS flight plan path). Five seconds
before the 30-second timer expires, the white reference line on ND flashes.
The selected azimuth for either terrain or weather analysis is not a fixed
bearing. When the aircraft turns, the white reference line sticks to a heading.
Practically, the white reference line moves with the compass rose on ND. When
the white reference line reaches the +/- 60° limits, the white reference line sticks
to the limit until the aircraft turns in the opposite direction.
Figure 7-42 illustrates the reference line behavior during a sequence of a 60° turn
to the left followed by a 30° turn to the right. The sequence starts while the
aircraft is heading to the North. The azimuth range is amber dashed and the
reference line is black.
Figure 7-42: Behavior of the reference line during turns
The following table compares the surveillance data displayed on ND and VD.
Navigation Display
ND
Vertical Display
VD
TAWS – Terrain
Yes
Yes
WXR – Ground mapping
Yes
No
WXR – Weather
Yes
Yes
WXR – Wind shear (PWS)
Yes
No
WXR – Turbulence
Yes
No
TCAS – Traffic
Yes
No
- 7-23 -
7 – Aircraft environment surveillance
7.1.8.3.
Getting to grips with Surveillance
PRIMARY FLIGHT DISPLAY (PFD)
AESS displays on PFD:
- Wind shear alerts (amber
W/S AHEAD caution or
red W/S AHEAD warning)
from the weather radar
function
- Terrain alerts from the
TAWS function
- TCAS orders on VSI.
Note: AESS provides terrain
indications on PFD contrary
to EGPWS or T2CAS that
illuminates
the
PULL
UP/GPWS pushbutton.
Figure 7-43: AESS indications on A380 PFD
7.1.8.4.
AURAL ALERTS
AESS provides the same aural alerts as the ones provided by stand-alone
systems:
- For TCAS alerts, refer to 3.1.7.2 – TCAS Aural Alerts
- For TAWS alerts, refer to 4.1.5 – TAWS Indications (see EGPWS)
- For WXR alerts, refer to 6.1.7 – Weather Radar Indications.
7.1.9.
AESS CONTROLS
All AESS controls are common to Captain and First Officer, except the following
that are limited to onside displays:
- KCCU: SURV key
- EFIS CP settings: display and range selection
- WXR SURV panel settings: elevation/tilt, gain, VD azimuth
- WXR MFD SURV CONTROLS settings: elevation/tilt, gain, mode
(WX/MAP), WX ON ND.
- 7-24 -
Getting to grips with Surveillance
7.1.9.1.
7 – Aircraft environment surveillance
KCCU SURV KEY
The KCCU SURV key is a shortcut to the MFD SURV page.
Refer to Figure 5-15 for the global KCCU picture.
Figure 7-44:
KCCU SURV key
7.1.9.2.
EFIS CONTROL PANEL (EFIS CP)
With the EFIS CP, in addition to the
range selection, the flight crew can
select the information to be displayed
on ND and VD (if available):
- WX: Weather, or
- TERR: Terrain, or
- TRAF: Traffic.
The
flight
crew
cannot
simultaneously select WX and
TERR.
Figure 7-45: EFIS Control Panel
7.1.9.3.
SURV PANEL
With the SURV panel, the flight crew
can:
- TCAS 5: Select TCAS modes (ABV,
BLW or NORM, and TA only or
TA/RA)
- TAWS: Deactivate the visual and
aural alerts of the TAWS Mode 5 –
Excessive glide slope deviation
- WXR:
Manually
set
the
elevation/tilt 6, gain or VD azimuth
(these settings for CAPT and F/O
are independent) or activate the
WXR AUTO mode 7
- AESS: Select the function groups
(WXR/TAWS 1 or 2, XPDR/TCAS 1
or 2).
Figure 7-46: AESS Control Panel
7.1.9.4.
SURV PAGES ON MFD
Two pages relative to AESS are available on MFD:
- The SURV CONTROLS page
- The SURV STATUS & SWITCHING page.
5
AESS does not support the THRT function (refer to 3.1.8 – TCAS Controls).
The flight crew uses the WXR ELEVN knob to manually set an elevation or tilt value. Refer to FCOM
for more details.
7
The flight crew pushes the WXR ELEVN knob to activate the WXR AUTO mode.
6
- 7-25 -
7 – Aircraft environment surveillance
Getting to grips with Surveillance
7.1.9.4.1.
CONTROLS Page
The flight crew controls all the AESS functions (XPDR, TCAS, WXR, TAWS) through
the MFD SURV CONTROLS page. On this page, the flight crew can modify the
SQWK code. However, for routine SQWK code changes, the flight crew can easily
modify the SQWK code and send the IDENT signal in the RMP SQWK page (refer
to 7.1.9.5 – SQWK Page on RMP).
At any time, the flight crew can reset
the default settings (the ones shown
in Figure 7-47) with the DEFAULT
SETTINGS button in the bottom right
corner. A dialog box pops up to
confirm the reversion to default
settings. When the flight crew resets
the default settings, the AESS keeps
the current SQWK code.
Figure 7-48: DEFAULT SETTINGS
confirmation
Figure 7-47: MFD SURV CONTROLS page
7.1.9.4.2.
STATUS & SWITCHING
Page
Through the MFD SURV STATUS &
SWITCHING page (refer to Figure 7-49),
the flight crew can dispatch the function
groups on AESU 1 or 2 according to the
detected failures.
This page is a back up of the AESS Control
Panel for the selection of function groups.
Figure 7-49: MFD SURV STATUS &
SWITCHING page
- 7-26 -
Getting to grips with Surveillance
7.1.9.5.
7 – Aircraft environment surveillance
SQWK PAGE ON RMP
On the RMP, the flight crew can:
- Modify the SQUAWK code in the SQWK page
- Activate the IDENT function from the SQWK page
- Check the transponder operating mode (AUTO, ON or STBY) either in
the SQWK page or in the message line of the VHF, HF, or TEL page.
In compliance with the AIRBUS dark cockpit philosophy, the AUTO mode, which is
the normal mode, is not indicated in the message line.
Figure 7-50: Transponder indications on RMP
7.2.
OPERATIONAL RECOMMENDATIONS FOR AESS
This paragraph of operational recommendations is intentionally non-exhaustive. For
more recommendations, please check your FCOM and/or FCTM as they are more
frequently updated.
7.2.1.
7.2.1.1.
FOR THE AIRLINE
TRANSPONDER FUNCTION
Refer to 2.5 – Operational Recommendations for Transponder.
7.2.1.2.
TCAS FUNCTION
Refer to 3.2 – Operational Recommendations for TCAS.
7.2.1.3.
TAWS FUNCTION
In addition to recommendations provided in 4.2 – Operational Recommendations
for TAWS, here are some recommendations specific to the A380 aircraft.
•
During the training, pay special attention to the Vertical Display (VD) (e.g.
automatic ground de-cluttering, generation of the vertical terrain view).
- 7-27 -
7 – Aircraft environment surveillance
7.2.1.4.
Getting to grips with Surveillance
WEATHER RADAR FUNCTION
In addition to recommendations provided in 6.2 – Operational Recommendations
for Weather Radar, here are some recommendations specific to the A380 aircraft.
•
During the training, pay special attention to the Vertical Display (VD) (e.g. 3D
buffering, generation of the vertical weather view).
7.2.2.
FOR THE FLIGHT CREW
• Be aware of the automatic management of AESS functions per flight phase
(e.g. WXR automatically turns off 60 s after touchdown). Refer to your FCOM
for more details.
7.2.2.1.
TRANSPONDER FUNCTION
Refer to 2.5 – Operational Recommendations for Transponder.
7.2.2.2.
TCAS FUNCTION
Refer to 3.2 – Operational Recommendations for TCAS.
7.2.2.3.
TAWS FUNCTION
In addition to recommendations provided in 4.2 – Operational Recommendations
for TAWS, here are some recommendations specific to the A380 aircraft.
•
•
Fly all flight phases with all TAWS settings to ON (i.e. DEFAULT SETTINGS)
except when:
- The airport is not in the TAWS database and the aircraft is within 15
NM from that airport, or
- The approach procedure is known to produce erroneous TAWS alerts.
Be aware of the mechanism involved in the generation of the vertical
terrain view (e.g. along flight plan, along track, along selected azimuth,
atmospheric influences on barometric elevations)
7.2.2.4.
WEATHER RADAR FUNCTION
In addition to recommendations provided in 6.2 – Operational Recommendations
for Weather Radar, here are some recommendations specific to the A380 aircraft.
•
•
Remember that it may take up to 30 seconds to build up the weather picture
at the first weather radar activation (e.g. before take-off run or switching
between SYS 1 and 2).
Be aware of the mechanism involved in the generation of the vertical
weather view (e.g. along flight plan, along track, along selected azimuth, on
path and off path weather, atmospheric influences on barometric elevations).
7.3.
REGULATIONS FOR AESS
The interpretation of regulations in this paragraph is limited to AIRBUS aircraft at
the time of writing this brochure.
- 7-28 -
Getting to grips with Surveillance
7 – Aircraft environment surveillance
The A380 AESS proposes an integrated solution for surveillance functions with
some enhancements. Nevertheless, the AESS elementary functions are quite
similar to the non-integrated surveillance functions described in the previous
chapter (i.e. transponder, TCAS, TAWS, WXR). Therefore, the operational
requirements are the same.
7.3.1.
TRANSPONDER FUNCTION
Refer to 2.6 – Regulations for Transponder.
7.3.2.
TCAS FUNCTION
Refer to 3.3 – Regulations for TCAS.
7.3.3.
TAWS FUNCTION
Refer to 4.3 – Regulations for TAWS
7.3.4.
WEATHER RADAR FUNCTION
Refer to 6.3 – Regulations for Weather Radar.
7.4.
MANUFACTURERS FOR AESS
Honeywell and AIRBUS jointly developed the A380 AESS to integrate all
surveillance systems in one. Figure 7-1 provides a simplified view of the AESS
architecture. Functions supported by the AESS are derived from elementary
Honeywell products:
- XPDR from TRA 67A Mode S transponder,
- TCAS from TPA 100A TCAS,
- TAWS from EGPWS,
- WXR from RDR 4000 weather radar.
7.5.
FUTURE SYSTEMS
7.5.1.
AIRBORNE TRAFFIC SITUATIONAL AWARENESS (ATSAW)
The A380 AESS is already capable to broadcast ADS-B OUT data, and is expected
to implement the ATSAW application as described in 3.6 – Description of ATSAW.
The ATSAW application makes the most of ADS-B IN data to improve the traffic
awareness. The interactivity of the ATSAW application will be improved thanks to
the interfaces provided by the A380 cockpit (i.e. KCCU).
- 7-29 -
7 – Aircraft environment surveillance
Getting to grips with Surveillance
Please bear in mind…
Description
The AESS is an integrated surveillance system on A380 aircraft. It includes
the transponder, the TCAS, the TAWS and the weather radar with PWS. The TAWS
and the weather radar use the Vertical Display (VD) at best to enhance the
flight crew awareness on terrain and weather.
Therefore, the AESS is also able to display on VD the terrain and weather along
the path followed by the aircraft (flight plan, track) or the azimuth selected by the
flight crew. The weather radar also introduces, thanks to the 3D buffer, the onpath and off-path weather concept, the weather view at a selected altitude
(elevation mode).
The AESS controls are distributed on the AESS Control Panel, the EFIS CP, the
MFD SURV page and the RMP SQWK page.
Operational recommendations
Operational recommendations regarding the AESS functions are the same as the
ones provided for the elementary systems (i.e. XPDR, TCAS, TAWS, WXR). The
VD introduces new logics and features. Therefore, a special attention should
be paid to mechanisms introduced by the VD.
Refer to 7.2 – Operational Recommendations for AESS.
Regulations
Regulations for the integrated AESS are the same as for elementary systems (i.e.
XPDR, TCAS, TAWS, WXR).
Future systems
To keep pace with the deployment of the ADS-B technology, the AESS is expected
to implement the ATSAW applications for enhanced traffic awareness.
- 7-30 -
Getting to grips with Surveillance
Appendices
APPENDICES
Appendix
Appendix
Appendix
Appendix
Appendix
Appendix
Appendix
Appendix
A
B
C
D
E
F
G
H
– Worldwide ADS-B implementation
– ADS-B phraseology
– ATSAW In Trail Procedure (ITP)
- ATSAW Visual Separation on Approach (VSA)
– NUC, NAC, NIC, SIL
– Identification of an aircraft
– Aviation meteorology reminders
– Low level Wind shear effects on aircraft performances
- A-1 -
A-2
B-1
C-1
D-1
E-1
F-1
G-1
H-1
Appendix A
Getting to grips with Surveillance
APPENDIX A – WORLDWIDE ADS-B IMPLEMENTATION
This appendix provides a global view on the main implementation of ADS-B
worldwide. ADS-B is an emerging technology and its implementation is
concentrated in Europe, USA, Australia and Asia at the time of writing the
brochure. Some local implementations exist where ADS-B is more profitable than
SSR (e.g. the French La Réunion island, Indian Ocean).
Mandate dates for ADS-B are provided for information only. Refer to the
appropriate Authority for the final dates.
A.1. THE EUROPEAN CASCADE PROGRAM
A.1.1. DESCRIPTION
- Europe progressively implements all ADS-B applications in the frame of the
CASCADE program. The CASCADE program is one of the first bricks to found
future ATM operations to be implemented in SESAR.
The first operational approvals for ADS-NRA were delivered late 2007. At the time
of writing the brochure, standards for ADS-B RAD, ATSA VSA and ATSA ITP are
being finalized before pre-operational validation. EASA envisages an ADS-B
mandate in 2015.
A.1.2. WEBSITE
Details on SESAR may be found at http://www.sesarju.eu.
Details on the CASCADE program may be found at
http://www.eurocontrol.int/cascade/public/subsite_homepage/homepage.html
A.2. THE FAA SURVEILLANCE AND BROADCAST SERVICES PROGRAM
The FAA launched the program in 2005 for the implementation of ADS-B over the
US territory. ADS-B is a crucial component of the US Next Generation Air
Transportation system (NGATS or NextGen).
A.2.1. DESCRIPTION
The FAA deploys the ADS-B coverage in two segments:
- Segment 1 includes Ontario (CA), Garden City (KS), North Platte (NE),
Kansas City (KS), Louisville (KY), Gulf of Mexico, Philadelphia (PA), Bethel Area
(AK), Anchorage (AK), and Juneau (AK). The first operational sites should start
in Q3 2009, and the Segment 1 deployment should end in Q3 2010.
- Segment 2 covers the entire US territory. The deployment of ADS-B in
Segment 2 should start from 2010 and should end in 2013. An avionics
equipage rate of 26% is expected by 2014 and a full equipage rate by 2020.
- A-2 -
Getting to grips with Surveillance
Appendix A
As proposed by the FAA NPRM released in October 2007, ADS-B would be
mandatory in the following airspaces:
- Class A, Class B, Class C, Class E above 10 000 ft,
- From the surface to 10 000 ft within 30 NM of specified busy airports, and
- In the Gulf of Mexico above 3 000 ft, within 12 NM from the coast.
The FAA plans an ADS-B mandate in 2020.
A.2.2. WEBSITE
Details on NextGen may be found at http://www.jpdo.gov/index.asp.
Details on the Surveillance and Broadcast Services program may be found at
http://www.faa.gov/about/office_org/headquarters_offices/ato/service_units/enro
ute/surveillance_broadcast/.
A.3. THE AUSTRALIAN ADS-B UPPER AIRSPACE PROGRAM (UAP)
A.3.1. DESCRIPTION
Airservices Australia is currently deploying ADS-B ground stations across
Australia. Combined with existing SSRs, deployed ADS-B ground stations will
provide an air traffic surveillance capability over the entire Australian territory.
The air traffic surveillance will be available above FL 300 (refer to Figure A - 1).
The objective of the program is to provide ADS-B equipped aircraft with increased
safety and operational flexibility in non-radar airspace. ADS-B equipped aircraft
will also be afforded operational priority in the ATC system.
The ADS-B UAP plans the
installation
of
28
ADS-B
ground stations at remote
locations in Australia, colocated with existing radio
communication facilities.
The Australian Advanced Air
Traffic System (TAAATS) is
being upgraded to process
1000
ADS-B
flights
simultaneously from up to 200
ground stations. TAAATS will
also use ADS-B technology to
provide air traffic controllers
with automated safety alerting
capabilities and will continually
monitor an aircraft's assigned
route and altitude for any
discrepancies.
Figure A - 1: Australian ADS-B coverage
- A-3 -
Appendix A
Getting to grips with Surveillance
The ADS-B UAP also plans the purchase of a new Receiver Autonomous Integrity
Monitoring (RAIM) system. The RAIM system will provide controllers with realtime information on Global Navigation Satellite System integrity.
The Upper Airspace Program may be expanded to provide additional ADS-B
coverage and services below FL300 at a later date.
At the time of writing the brochure, Airservices Australia operates ADS-B on a
voluntary basis. CASA Australia mandates the carriage of ADS-B from
December 12th 2013 at or above FL 290.
A.3.2. WEBSITE
For more details, please refer to
https://www.airservicesaustralia.com/projectsservices/projects/adsb/default.asp.
A.4. DEPLOYMENT OF ADS-B IN ASIA
A.4.1. DESCRIPTION
In the Bay of Bengal and in the Asian regions, several trials are currently in
progress. The following is some examples of activities in progress:
- Fiji domestic airspace: Procedural separations are in force. ADS-B is seen as
a key enabler for an optimized management of traffic in the Fiji domestic
airspace. Surveillance based on ADS-B should start in 2009-2010.
- Chengdu–Lhasa route (China): ADS-B is being implemented along the
Chendu-Lhasa route to provide a reliable and continuous control service by
2015. Presently, procedural separations are applied. Four ADS-B stations are
planned and should be validated in the course of 2009.
- Incheon International Airport (South Korea): ADS-B is intended to cope
with the increasing traffic and to enhance the final approach and surface
monitoring. ADS-B operations should start in the course of 2008. At the time
of writing the brochure, 35 ADS-B transmitters had been installed on airport
ground vehicles (e.g. fire and rescue, emergency, safety check, airline support,
etc).
- Pakistan airspace: Most of the Pakistan airspace is radar covered. However,
some gaps in the west and northern mountain regions, as well as in the south
seaward part of the country, remain. ADS-B is considered to fill in these gaps.
Trials are expected to start in late 2008 or early 2009.
A.4.2. WEBSITE
For more details, please refer to the materials of the Automatic Dependent
Surveillance – Broadcast (ADS-B) Seminar and The Meeting Of ADS-B Study and
Implementation Task Force available at http://www.icao.or.th/welcome.html (click
on the desired year of the MEETING SCHEDULE frame in the middle of the left
panel, then search for the ADS-B SITF meeting).
- A-4 -
Getting to grips with Surveillance
Appendix A
A.5. ADS-B NRA IN THE HUDSON BAY (CANADA)
A.5.1. DESCRIPTION
In July 2006, NAV CANADA announced its intention to implement ADS-B over the
Hudson Bay by the end of 2008 (refer to Transport Canada AIC 18/07, see
References). At the time of writing the brochure, 35 000 flights a year crossed the
Hudson Bay without surveillance services. NAV CANADA retained ADS-B as the
solution to fill in the surveillance gap in this area. ADS-B presents significant
benefits compared to SSR in terms of quality, reliability and costs, but it also
requires operators crossing this area to be equipped with appropriate avionics.
In 2007, 50 to 60% of the traffic over the Hudson Bay were technically capable to
broadcast ADS-B data. IATA expects this portion of traffic to increase up to 90%
in 2010.
NAV CANADA currently leads a
consultation with its customers
in
order
to
prepare
the
implementation of ADS-B over
the
Hudson
Bay.
First
operational
ADS-B
services
started
in
January
2009.
Transport Canada plans an
ADS-B mandate over the
Hudson Bay in mid 2009
above FL 350.
Figure A - 2: ADS-B coverage in Hudson Bay,
Canadian Atlantic coast, and Greenland
Five stations are planned in the
Hudson
Bay:
Rankin
Inlet,
Churchill,
Fort
Severn,
Povungnituk and Coral Harbor
(white areas in Figure A - 2).
In the future, NAV CANADA plans to expand ADS-B to the Canadian Atlantic coast
(yellow areas in Figure A - 2), the Gander airspace over Greenland (magenta
areas in Figure A - 2), and eventually over the entire country.
A.5.2. WEBSITE
For more details, please refer to:
http://www.navcanada.ca/NavCanada.asp?Language=en&Content=ContentDefinit
ionFiles%5CServices%5CANSPrograms%5CADS-B%5Cdefault.xml
- A-5 -
Getting to grips with Surveillance
Appendix B
APPENDIX B – ADS-B PHRASEOLOGY
The following table provides an overview of the ADS-B phraseology as per the
ICAO Doc 4444 – PANS ATM, 15th Edition, 2007, Chapter 12 – Phraseologies (see
References).
Note: The implementation of ADS-B operations may locally change. Refer to AIP
for specific regional procedures.
Circumstances
Radar
ADS-B
12.4.1.10. Termination or RADAR
SERVICE IDENTIFICATION
Radar or ADS-B service
TERMINATED
[DUE TERMINATED
[DUE
(reason)] (instructions)
(reason)] (instructions)
12.4.1.11. Radar or ADS- SECONDARY
RADAR ADS-B
OUT
OF
B equipment degradation
OUT
OF
SERVICE SERVICE
(appropriate
(appropriate information information as necessary)
as necessary)
PRIMARY RADAR OUT
OF
SERVICE
(appropriate information
as necessary)
12.4.3.1. & 12.4.3.2. To ADVISE TRANSPONDER ADVISE
request the capability of CAPABILITY
CAPABILITY
the
SSR
or
ADS-B
equipment
ADS-B
To advise the capability of TRANSPONDER
ADS-B
TRANSMITTER
the
SSR
or
ADS-B (ALPHA, CHARLIE or (data link*);
equipment
SIERRA as shown in
the flight plan)
ADS-B RECEIVER (data
link*)
* As AIRBUS aircraft use
the 1090 ES data link,
TEN NINETY DATA LINK
should be announced.
NEGATIVE
TRANSPONDER
12.4.3.4. & 12.4.3.5. To RESET
SQUAWK
request
the
pilot
to [(mode)] (code)
reselect
the
assigned
mode and code or the
aircraft identification
- B-1 -
NEGATIVE ADS-B
RE-ENTER [ADS-B or
MODE S] AIRCRAFT
IDENTIFICATION
Note: Not able to comply
with some FMS standards
(see note in 2.5.2.2 – For
the Flight Crew). Refer to
AIP
for
alternative
Appendix B
Circumstances
Getting to grips with Surveillance
Radar
ADS-B
procedures.
Read back
RESETTING
(code)
(mode) Not defined
12.4.3.7. To request the SQUAWK
[(code)] TRANSMIT
ADS-B
operation of the IDENT [AND] IDENT
IDENT
feature
Note: Transponder and
ADS-B transmitter are
coupled
on
AIRBUS
aircraft.
Activate
the
IDENT function as in
radar coverage.
12.4.3.10. To request the STOP
termination
of [TRANSMIT
transponder or ADS-B ONLY]
transmitter operation
SQUAWK STOP
ADS-B
ADS-B TRANSMISSION
[SQUAWK
(code)
ONLY]
Note: Not able to comply with on AIRBUS aircraft.
Refer to AIP for alternative procedures.
12.4.3.11. To request SQUAWK CHARLIE
transmission of pressurealtitude
12.4.3.13. To request STOP
termination of pressure- CHARLIE
altitude
transmission INDICATION
because
of
faulty
operation
- B-2 -
TRANSMIT
ADS-B
ALTITUDE
Note: Transponder and
ADS-B transmitter are
coupled
on
AIRBUS
aircraft.
Activate
the
altitude reporting as in
radar coverage.
SQUAWK STOP ADS-B ALTITUDE
WRONG TRANSMISSION
[(WRONG
INDICATION,
or
reason)]
Note: Transponder and
ADS-B transmitter are
coupled
on
AIRBUS
aircraft. Refer to 2.5.2.2
– For the Flight Crew.
Getting to grips with Surveillance
Appendix C
APPENDIX C – ATSAW IN TRAIL PROCEDURE (ITP)
This appendix provides details on ITP with the use of ATSAW. This appendix:
- Gives the definitions of terms commonly used for ITP
- Describes the ITP procedure in details
- Gives a practical example with cockpit interfaces.
The ITP description is compliant with standards published at the time of
writing the brochure. The readers must ensure to take into account any
updates of ITP standards.
C.1. DEFINITIONS
Ground
Speed Difference of ground speed between the ITP aircraft and the
Reference Aircraft. The ground speed differential is positive
Differential
when aircraft are getting closer.
ITP Aircraft
Aircraft:
- Fully qualified in terms of equipment, operator, and
flight crew qualification to conduct an ITP
- That considers a flight level change.
ITP Criteria
Refer to C.2.6 – ITP Criteria.
ITP Distance
Refer to C.2.5 – ITP Distance.
ITP Volume
Refer to C.2.3 – ITP Volume.
Other Aircraft
Aircraft that are not either the ITP aircraft or the Reference
Aircraft.
Qualified
data
ADS-B ADS-B data that meet accuracy and integrity requirements
for ITP.
Reference Aircraft
One or two aircraft in the ITP volume but not at the desired
flight level:
- With qualified ADS-B data
- That meet the ITP criteria
- That will be identified to ATC by the ITP Aircraft in the
ITP clearance request.
Same Direction
Refer toC.2.2 – Aircraft on the Same Direction.
C.2. PROCEDURE
C.2.1. ITP SEQUENCE
1. To initiate an ITP maneuver, the flight crew must check that the ITP
criteria (refer to C.2.6 – ITP Criteria) are met. The ITP criteria ensure that
the ITP Aircraft and the Reference Aircraft do not get closer than the ITP
separation minimum (10 NM).
- C-1 -
Appendix C
Getting to grips with Surveillance
ITP distance
ITP separation minimum
Figure C - 1: ITP separation minimum
2. When the ITP criteria are met, the flight crew may request an ITP
clearance. The ITP request contains the identification of the Reference
Aircraft and the range to these aircraft. The ATC controller checks that
conditions are met to maintain safe separations between ITP and Reference
Aircraft.
3. When these conditions are met, the ATC controller may deliver the
clearance.
4. When the ATC clearance is received, the flight crew must re-check that
the ITP speed/distance criteria are still met before initiating the ITP
maneuver.
The ATC controller remains responsible for the aircraft separations.
Therefore, the flight crew is not required to monitor the separations with the
Reference Aircraft during the ITP maneuver.
C.2.2. AIRCRAFT ON THE SAME DIRECTION
The definition of the term Same Direction is
derived from the term Same Track given in
ICAO PANS-ATM, Doc 4444 (see References).
Aircraft are on a same direction when the
difference of track angles is:
- Less than 45°, or
- More than 315°.
Refer to Figure C - 2.
C.2.3. ITP VOLUME
The ITP criteria apply to aircraft that are in
the ITP volume. The ITP volume is centered
on the ITP Aircraft and defined as follows:
- Height: 4 000 ft above the aircraft in
Figure C - 2: Same direction
climb or below the aircraft in descent.
- Length: 160 NM. It is equal to procedural longitudinal separations (10 min or
80 NM) behind and ahead of the aircraft.
- Width: 40 NM. This width ensures that aircraft on parallel tracks are excluded
of the ITP process (e.g. when lateral separations of 30 NM are applied).
- C-2 -
Getting to grips with Surveillance
Appendix C
Figure C - 3: ITP volume
Figure C - 3 illustrates the ITP volume for an ITP climb.
The ITP maneuver is vertically limited to 4 000 ft (+ 4 000 ft in climb, - 4 000 ft
in descent). Therefore, Reference Aircraft may be between 1 000 and 3 000 ft
above (in climb) or below (in descent) the cruise flight level. Refer to Figure C - 4.
+4 000 ft
+3 000 ft
+2 000 ft
ITP
distance
Standard Long.
Separations
+1 000 ft
CRZ FL
80 NM
ITP
distance
-1 000 ft
-2 000 ft
-3 000 ft
-4 000 ft
= ITP Aircraft
= Reference Aircraft
Figure C - 4: Side view of ITP volume
- C-3 -
= Other aircraft
Appendix C
Getting to grips with Surveillance
C.2.4. ITP GEOMETRIES
The maximum number of Reference Aircraft is limited to two. Reference Aircraft
are at any flight levels between the initial and the desired flight levels. The
following illustrations describe some ITP geometries. Other geometries refer to
two Reference Aircraft that are both behind or both ahead of the ITP
Aircraft.
ITP climb BEHIND
ITP climb AHEAD OF
ITP climb
BEHIND/AHEAD OF
ITP descent BEHIND
ITP descent AHEAD OF
ITP descent
BEHIND/AHEAD OF
Figure C - 5: ITP geometries
C.2.5. ITP DISTANCE
The ITP distance is the difference of
distance to a common point along
tracks of ITP and Reference Aircraft.
Refer to Figure C - 6. Figure C - 7
provides the calculation methods of
the
ITP
distance
for
different
geometries. For more details, refer to
ICAO PANS-ATM, Doc 4444, Chapter 5
– Separations Methods and Minima
(see References).
The ADS-B distance computed
thanks to ADS-B information is the
distance between the GPS positions of
both aircraft.
The TCAS range is the distance
computed by TCAS between the
current aircraft positions.
Figure C - 6: ITP distance
- C-4 -
Getting to grips with Surveillance
Appendix C
Note: It has to be noted that aircraft are separated by thousands of feet vertically
and dozens of nautical miles horizontally. As a rough order of magnitude:
1 000 ft
= 0.016 . ADS-B distance does not differ much from TCAS range.
10 NM
Figure C - 7: ITP distances with different geometries
- C-5 -
Appendix C
Getting to grips with Surveillance
C.2.6. ITP CRITERIA
To ensure that the ITP Aircraft and the Reference Aircraft do not get closer than
the ITP separation minimum (10 NM), the following conditions must be met.
Criteria
Checked by
1. A maximum of two Reference Aircraft are in the ITP
volume.
ATSAW
2. Reference Aircraft must send qualified ADS-B data (refer
to 3.6.4.2.4 – Combination of TCAS and ADS-B
Information).
ATSAW
3. The requested flight level must be within 4 000 ft
from the initial flight level.
ATSAW
4. The ITP distance and the positive ground speed differential
must meet the criterion 4.a) or 4.b) below.
ITP distance
Positive GS differential
4.a)
Greater than 15 NM
Less than 20 kt
4.b)
Greater than 20 NM
Less than 30 kt
ATSAW
5. The ITP Aircraft must be climb or descent at 300 ft/min
minimum or any higher rate as required by the
appropriate authority.
Flight crew
6. The ITP Aircraft must be capable to maintain its
assigned Mach number during the ITP maneuver.
Flight crew
7. The ITP and Reference Aircraft must be on the same
ATSAW and
direction.
ATC controller
8. The ITP Aircraft must not be a Reference Aircraft in
ATC controller
another ITP clearance.
9. The positive Mach differential is less than 0.04.
ATC controller
10.Procedural separations are met with Other Aircraft at
all flight levels between the CRZ FL and the desired FL ATC controller
(inclusive).
11.Reference Aircraft must not maneuver (i.e. change of
speed, flight level or direction) during the ITP maneuver. A
change of heading to remain on the same route as the ITP
ATC controller
Aircraft is not considered as a maneuver. A change of
Reference Aircraft speed that does not increase the
positive Mach differential is not considered as a maneuver.
In Figure C - 4, the ITP Aircraft is:
- Able to make a climb AHEAD OF. The ITP distance exceeds the minimum
- Not able to make a descent BEHIND. The ITP distance is less than required.
- C-6 -
Getting to grips with Surveillance
Appendix C
C.3. EXAMPLE
The following sections describe the ITP step by step from a cockpit perspective. In
any cases, refer to AIP.
C.3.1. PF:
CHECK
THE
AIRCRAFT
PERFORMANCES
When the flight crew decides a FL
change,
PF
checks
the
aircraft
performances on MCDU FMS PROG
page.
When the aircraft is below the REC
MAX FL, the aircraft is able to:
- Climb at 300 ft/min minimum
- Maintain its speed during the climb.
Figure C - 8: MCDU PROG page
C.3.2. PF: INITIATE THE ITP
In the MCDU MENU, PF selects TRAF
(LSK 5R in Figure C – 9) to display the
TRAFFIC LIST page. In the TRAFFIC
LIST page, PF selects IN TRAIL
PROCEDURE (LSK 5R in Figure C – 10)
to display the ITP TRAFFIC LIST page.
In the ITP TRAFFIC LIST, PF enters the
desired FL in the DESIRED FL field (LSK
1L in Figure C - 11).
Figure C – 9: Select TRAF in MCDU
MENU
Figure C – 10: Select IN TRAIL
PROCEDURE
Figure C - 11: Enter desired FL in LSK
1L
- C-7 -
Appendix C
Getting to grips with Surveillance
C.3.3. PF: CHECK THE ITP OPPORTUNITY AND IDENTIFY REFERENCE AIRCRAFT
When PF entered the desired FL, the
ATSAW function (refer to Figure C - 12):
- Checks that the ITP criteria are met
as in C.2.6 – ITP Criteria
- Indicates if the ITP is possible or not
(LSK 1R).
- Displays the aircraft in the ITP
volume.
PF checks the ITP opportunity (possible
or not and time) and identifies the
Reference Aircraft in the ITP Traffic List
(ITP distance, relative position, and
flight number).
Figure C - 12: Check the ITP
opportunity and identify Reference
Aircraft
C.3.4. PNF: REQUEST THE ATC CLEARANCE
PF informs PNF that ITP is possible and
indicates the Reference Aircraft (ITP
distance, position, and flight number).
PNF requests an ITP clearance to ATC by
CPDLC.
PNF
applies
a
specific
phraseology in the CPDLC message. See
notes below.
Figure C - 13: Enter desired FL in the
CPDLC vertical request
It is recommended to edit the free text
as follows (refer to Figure C - 15):
- LSK 1L: ITP
- LSK 2L: The ITP distance/relative
position/flight number of the first
Reference Aircraft
- LSK 3L: The ITP distance/relative
position/flight number of the second
Reference Aircraft (if any).
This method provides a clear view of
entered data and permits the flight crew
to rapidly check and/or correct one line.
- C-8 -
Figure C - 14: Go directly to the 2nd
TEXT page with the SLEW keys (←→)
Getting to grips with Surveillance
Appendix C
Figure C - 15: Enter ITP data and
transfer the message to DCDU
Figure C - 16: Send the message from
DCDU
The flight crew applies the usual procedures relative to CPDLC (e.g. cross-check,
efficient management of DCDU). For more details on CPDLC, refer to Getting
to Grips with FANS (see AIRBUS References).
Note 1: At the time of writing the brochure, the CRISTAL ITP consortium
suggested an ITP phraseology to ICAO. ICAO evaluates the suggested ITP
phraseology and should provide some recommendations. Figure C - 16 uses the
suggested ITP phraseology. Note that the ITP Traffic list displays the information
in the same sequence as in the suggested ITP phraseology (i.e. ITP
distance/relative position/flight number, see Figure C - 12 and Figure C - 16).
Note 2: The CRISTAL ITP consortium(refer to C.5 – CRISTAL ITP) considers
CPDLC as more efficient than HF voice to request an ITP clearance for the
following reasons:
- CPDLC is faster than HF voice in terms of transmission time.
- CPDLC prevents errors that could occur with the poor transmission quality of
HF voice, especially for the transmission of flight numbers.
- CPDLC is a Direct Controller-Pilot Communication (DCPC) media.
C.3.5. PF: PERFORM THE ITP
When the flight crew receives the ITP clearance (refer to Figure C - 17), PF must
re-check that the ITP is still possible in the ITP TRAFFIC LIST page (refer to Figure
C - 12). PF re-checks:
- Aircraft performances
- Green ITP POSSIBLE in the ITP TRAFFIC LIST page.
If ITP is still possible, PNF accepts (i.e. WILCO) the ITP clearance by CPDLC. If a
report level instruction is included in the ITP clearance, the ATSU monitors the
aircraft FL (refer to Figure C - 18).
Then, PF starts the ITP maneuver without delay. The aircraft must:
- Climb at 300 ft/min minimum or any higher rate as required by the
appropriate authority
- Maintain its assigned Mach number.
- C-9 -
Appendix C
Getting to grips with Surveillance
Figure C - 17: ITP clearance
Figure C - 18: Accept the clearance
When the aircraft engages the ITP maneuver and is more than 300 ft from the
initial FL, the ATSAW function displays the message VERTICAL MANEUVER IN
PROGRESS in the ITP TRAFFIC LIST page (refer to Figure C - 19). The ATSU
triggers a report level message when the FL in the report level instruction is
reached (refer to Figure C - 20).
Figure C - 19: ITP TRAFFIC LIST page
during the ITP maneuver
Figure C - 20: Report level
Note 1: If ITP is no more possible when the flight crew receives the ITP
clearance, the flight crew must refuse the ITP clearance.
Note 2: If a problem occurs during the ITP maneuver, the flight crew must apply
the regional contingency procedures as required.
C.3.6. SPECIFIC CASES
When there is no Reference Aircraft in the ITP volume (refer to Figure C 21), the ATSAW function indicates that:
- The ITP is not applicable
- The flight crew should request a standard clearance.
The ATSAW function displays in the MCDU scratchpad the flight level and the
range of:
- An aircraft (ADS-B or not) that is at the desired FL in the ITP volume, or
- An ADS-B aircraft that is not on the same direction in the ITP volume..
- C-10 -
Getting to grips with Surveillance
Appendix C
However, the ATSAW function may display “ITP POSSIBLE” despite the non-ADS-B
aircraft. Indeed, the ATSAW function considers only ADS-B traffic to declare the
ITP possible or not possible.
The ATC controller remains responsible for the aircraft separation during
an ITP maneuver, for the following reasons:
- Some aircraft may not be equipped with an ADS-B OUT transmitter. Therefore,
the ATSAW function is not able to detect all surrounding aircraft.
Consequently, only the ATC controller has the knowledge of the entire traffic.
- The initial ATSAW function is not designed for self-separation.
Figure C - 21: ITP not applicable
Figure C - 22: Non-ADS-B aircraft in the
ITP volume
C.4. OPERATIONAL ENVIRONMENT
ITP can be applied in theory in any RVSM / Non-RVSM airspace where procedural
control is used. Conditions for operational approval include controller training to
ITP. For the procedure to provide the expected benefits, a non exhaustive list of
conditions are provided below:
- Separation standards with minima greater than 15 NM,
- Sufficient number of ADS-B OUT equipped aircraft
- Aircraft usually following similar routes (e.g. North Atlantic Organized Track
System).
C.5. CRISTAL ITP
CRISTAL ITP is a consortium with AIRBUS, Alticode, Eurocontrol, ISAVIA
(Icelandic ANSP) and NATS (UK ANSP). The objective of CRISTAL ITP is to
validate ITP. In March 2008, CRISTAL ITP performed a successful flight test with
an SAS commercial flight and an AIRBUS test aircraft. During the flight test, the
AIRBUS test aircraft performed different ITP maneuvers around the SAS aircraft.
The flight test occurred in the Reykjavik airspace under radar coverage to ensure
safe separations.
At the time of writing the brochure, CRISTAL ITP has proposed a PANS-ATM (ICAO
Doc 4444) amendment to introduce ATSA ITP to be validated by ICAO.
- C-11 -
Getting to grips with Surveillance
Appendix D
APPENDIX D - ATSAW VISUAL SEPARATION ON APPROACH (VSA)
D.1. PROCEDURE
With the introduction of ATSAW in the VSA procedure, the distinction is made
between three types of VSA procedure:
• The current VSA procedure without ATSAW
• The basic VSA procedure with ATSAW slightly modifies the flight crew
procedure. The ATC controller does not distinguish aircraft equipped with
ATSAW from aircraft not equipped with ATSAW. Therefore, the ATC
controller procedure is not modified. The flight crew uses ATSAW to visually
acquire the preceding aircraft and to maintain the visual separation.
• The advanced VSA procedure with ATSAW modifies the flight crew and
ATC controller procedures. With a new phraseology, the flight crew informs
the ATC controller that the preceding aircraft is identified with ATSAW but
not yet visually acquired out the window. Consequently, the ATC controller
is not required to update the traffic information until the visual contact by
the flight crew.
ATSAW significantly improves the VSA procedure by providing the following
parameters:
- The position and orientation of surrounding aircraft
- The flight identification of surrounding aircraft that can be correlated with ATC
transmissions
- The ground speed of surrounding aircraft that help anticipating sudden
deceleration of the preceding aircraft.
The following sections describe the VSA procedure as per the three types above.
The VSA procedure contains three steps:
1. The visual acquisition of the preceding aircraft
2. The clearance for maintaining the visual separation with the preceding aircraft
3. The maintenance of visual separation on approach with the preceding aircraft.
- D-1 -
Appendix D
Getting to grips with Surveillance
D.1.1. VISUAL ACQUISITION OF THE PRECEDING AIRCRAFT
Current VSA procedure
Basic VSA procedure
(Green italic is specific to the basic
procedure)
Advanced VSA procedure
(Blue italic is specific to the enhanced
procedure)
(Amber italic is specific to the basic and advanced procedure)
Initiation by the ATC controller
The ATC controller provides the flight crew with traffic information on the
preceding aircraft.
The flight crew looks out the window to visually acquire the preceding
aircraft.
The flight crew looks at the ND with the traffic display enabled (refer to
3.6.5.1.1 – TRAF ON/OFF) to detect the preceding aircraft.
o Visual contact
- The flight crew checks the consistency between the visual contact, the
ATSAW traffic information, and the ATC traffic information.
- The flight crew informs the
ATC
controller
that
the
preceding aircraft is in sight
(i.e. TRAFFIC IN SIGHT). Go
to the next step.
1
- The flight crew informs the
ATC
controller
that
the
preceding aircraft with its
flight number displayed on ND
is in sight (e.g. TRAFFIC
AIB1234 IN SIGHT 1).
- The ATC controller checks the
consistency between the flight
number of the preceding
aircraft provided by the flight
crew and the one on the
surveillance display.
If the flight numbers are
consistent, go to the next
step.
If the flight numbers are
not consistent, the ATC
controller informs the flight
crew that the flight number
is not correct and provides
the
traffic
information
again.
It means that the traffic is identified on ND thanks to ATSAW but the visual contact is not established.
At the time of writing the brochure, this new phraseology was not yet validated. ICAO recommendations
on this new phraseology will be published in the ICAO PANS-ATM, Doc 4444 (see References).
- D-2 -
Getting to grips with Surveillance
Appendix D
Current VSA procedure
Basic VSA procedure
(Green italic is specific to the basic
procedure)
Advanced VSA procedure
(Blue italic is specific to the enhanced
procedure)
(Amber italic is specific to the basic and advanced procedure)
o
No visual contact
- The flight crew reports to the
ATC
controller
that
they
continue
to
search
the
preceding
aircraft
(i.e.
LOOKING OUT)
- The flight crew asks the ATC
controller
for
traffic
information updates if the
visual contact is not quickly
achieved
- When the preceding is finally
in sight, the flight crew checks
the consistency between the
visual contact, the ATSAW
traffic information, and the
ATC traffic information.
- If the preceding aircraft is on
ND, the flight crew
Informs the ATC controller
that the preceding aircraft
is identified on ND (e.g.
LOOKING OUT AIB1234 2)
Continues to search the
preceding aircraft with the
support of the ATSAW
traffic information.
- The ATC controller checks the
consistency between the flight
number of the preceding
aircraft provided by the flight
crew and the one on the
surveillance display:
If the flight numbers are
consistent,
the
ATC
controller waits the flight
crew reports the traffic in
sight.
If the flight numbers are
not consistent, the ATC
controller informs the flight
crew that the flight number
is not correct and provides
the
traffic
information
again.
- The flight crew informs the ATC controller that the preceding aircraft is
finally in sight. Go to the next step.
2
At the time of writing the brochure, this new phraseology was not yet validated. ICAO
recommendations on this new phraseology will be published in the ICAO PANS-ATM, Doc 4444 (see
References).
- D-3 -
Appendix D
Getting to grips with Surveillance
Current VSA procedure
Basic VSA procedure
(Green italic is specific to the basic
procedure)
Advanced VSA procedure
(Blue italic is specific to the enhanced
procedure)
(Amber italic is specific to the basic and advanced procedure)
Initiation by the flight crew
The flight crew achieves a visual contact with the preceding aircraft with
visual information, ATSAW traffic information, and party line (transmissions
from the controller and other flight crews on the frequency).
When the preceding is in sight, the flight crew checks the consistency
between the visual contact and the ATSAW traffic information.
If the visual contact can be maintained, the flight crew:
o Informs the ATC controller that the preceding aircraft with its flight
number displayed on ND is in sight (e.g. PRECEDING TRAFFIC AIB1234
IN SIGHT).
o Requests a clearance for VSA procedure. Go to the next step.
D.1.2. CLEARANCE FOR THE MAINTENANCE OF THE VISUAL SEPARATION WITH THE
PRECEDING AIRCRAFT
Current VSA procedure
Basic VSA procedure
(Green italic is specific to the basic
procedure)
Advanced VSA procedure
(Blue italic is specific to the enhanced
procedure)
(Amber italic is specific to the basic and advanced procedure)
The ATC controller clears the flight crew:
o To maintain a visual separation with the preceding aircraft
o If needed, to continue on a visual approach.
The flight crew accepts or refuses the clearance. The flight crew can better
assess the ATC clearance with ATSAW.
If the flight crew accepts the clearance, go to the next step.
- D-4 -
Getting to grips with Surveillance
Appendix D
D.1.3. MAINTENANCE OF VISUAL SEPARATION ON APPROACH
Current VSA procedure
Basic VSA procedure
(Green italic is specific to the basic
procedure)
Advanced VSA procedure
(Blue italic is specific to the enhanced
procedure)
(Amber italic is specific to the basic and advanced procedure)
The flight crew:
o Flies the approach
o Looks at the preceding aircraft on ND with the traffic display enabled.
o Looks at the preceding aircraft out the window
o Decides if a maneuver is required based on visual information or ATSAW
traffic information
o Maneuvers the aircraft if required to maintain the visual separation.
The VSA procedures ends when the preceding aircraft lands.
If the visual contact is lost or the flight crew considers that the situation
becomes unsafe; the flight crew:
o Interrupts the approach
o Executes a missed approach
o Informs the ATC controller.
When a maneuver is required, the flight crew may adjust the speed or heading to
maintain an appropriate distance behind the preceding aircraft.
D.2. OPERATIONAL ENVIRONMENT
•
•
•
•
•
•
•
Approach under radar surveillance down to the ground
Ground surveillance with one SSR and one PSR
Communication between the flight crews and controllers via VHF voice
Traffic density from low to high
All types of runway configuration (e.g. single, independent parallel,
dependent parallel, etc)
Approach in VMC only
Preceding aircraft capable of ADS-B OUT.
- D-5 -
Getting to grips with Surveillance
Appendix D
APPENDIX E – NUC, NAC, NIC, SIL
The following table provides an overview of NUC/NAC/NIC/SIL values used in
ADS-B transmissions. It must be seen as for information only. For
specification purposes, refer to appropriate documents.
NUCP
0
1
2
3
4
Integrity
-HPL < 20 NM
HPL < 10 NM
HPL < 2 NM
HPL < 1 NM
5
HPL < 0.5 NM
6
HPL < 0.2 NM
7
HPL < 0.1 NM
8
9
NIC
0
1
2
3
4
5
6
7
8
9
10
11
Accuracy
-HFOM < 10 NM
HFOM < 5 NM
HFOM < 1 NM
HFOM < 0.5
NM
HFOM < 0.25
NM
HFOM < 0.1
NM
HFOM < 0.05
NM
HFOM < 10 m,
VFOM < 15 m
HFOM < 3 m,
VFOM < 4 m
Integrity Containment Limits
-RC < 20 NM
RC < 8 NM
RC < 4 NM
RC < 2 NM
RC < 1 NM
RC < 0.6 NM
RC < 0.2 NM
RC < 0.1 NM
RC < 75 m
RC < 25 m
RC < 7.5 m
SIL
0
1
2
3
NACP
0
1
2
3
4
5
6
7
8
9
10
11
- E-1 -
Probability of Exceeding
Containment Bounds for
NIC
Without
Being
Notified
(No Integrity)
< 10-3 per flight hour
< 10-5 per flight hour
< 10-7 per flight hour
Accuracy
-EPU < 10 NM
EPU < 4 NM
EPU < 2 NM
EPU < 1 NM
EPU < 0.5 NM
EPU < 0.3 NM
EPU < 0.1 NM
EPU < 0.05 NM
EPU < 30 m, VFOM < 45 m
EPU < 10 m, VFOM < 15 m
EPU < 3 m, VFOM < 4 m
Getting to grips with Surveillance
Appendix F
APPENDIX F – IDENTIFICATION OF AN AIRCRAFT
The following table lists the designation of the different codes used for the
identification of an aircraft in the ICAO literature and in AIRBUS cockpit.
ICAO
AIRBUS
Examples
Aircraft Identification
Flight Number entered into
Up to 7 characters, it is:
the FM INIT A page.
- The registration marking
F-OHAP
of the aircraft when:
In radiotelephony the call
sign used by the aircraft
will
consist
of
this
identification
alone
or
preceded by the ICAO
telephony designator for
the
aircraft
operating
agency;
The aircraft is not equipped
with radio.
- The ICAO designator for
AIB1234
the
aircraft
operating
agency followed by the
flight identification when
in radiotelephony the call
sign used by the aircraft will
consist of the ICAO telephony
designator for the operating
agency followed by the flight
identification.
Flight identification
Numerical part of the flight 1234
number (up to 4 characters).
Airline ID is the IATA 2-letter AU
code. Used for data link.
Flight ID
AU1234
Airline ID followed by the
flight identification (up to 6
characters). Used for data
link.
Registration Marking
It is the tail number.
Aircraft
Registration F-WWOW
Number (ARN)
Used for data link.
Aircraft Address
ICAO Code (data link) or 380338
A unique combination of 24 bits Mode
S
address (hexadecimal
- F-1 -
Appendix F
Getting to grips with Surveillance
ICAO
AIRBUS
Examples
available for assignment to an (transponder)
aircraft for the purpose of airground
communications,
navigation and surveillance.
format)
Call Sign
ICAO telephony designator for
the operating agency followed
by the flight identification.
“AIRBUS ONE
TWO
THREE
FOUR”
for
AIB1234
ICAO telephony designator
for the operating agency
Designator defined in ICAO Doc
8585.
“AIRBUS”
AIRBUS
for
Recommendations for the use of radiotelephony call signs are provided in ICAO
Annex 10, Volume II, Chapter 5 (see References). ICAO designators and
telephony designators for aircraft operating agencies are listed in ICAO Doc
8585 — Designators for Aircraft Operating Agencies, Aeronautical
Authorities and Services (see References).
- F-2 -
Getting to grips with Surveillance
Appendix G
APPENDIX G – AVIATION METEOROLOGY REMINDERS
This appendix provides some reminders about aviation meteorology. For further
details, please refer to typical aviation meteorology courses.
G.1. STANDARD ATMOSPHERE
The figure below illustrates the
different
layers
of
the
atmosphere and the variation
of standard temperature with
altitude. Interesting clouds for
transport aviation are in the
Troposphere.
However, specific clouds may
form
in
the
Stratosphere
(nacreous clouds also called
mother-of-pearl clouds), and in
the
Ionosphere
(noctilucent
clouds or NLC). Auroras also
appear in the Ionosphere. The
top of a cumulonimbus may
penetrate the Tropopause due to
the inertia of a rapid expansion.
Figure G - 1: Standard atmosphere
Below 0°C, super-cooled water may coexist with ice crystals. Below -40°C, there
are only ice crystals.
- G-1 -
Appendix G
Getting to grips with Surveillance
G.2. THUNDERSTORMS
G.2.1. FORMATION
The thunderstorm is a cumulonimbus that develops up to a stage with an anvil
top. However, a cumulonimbus may have all the dangerous characteristics of a
thunderstorm (i.e. lightnings, hail, turbulence).
The development of a thunderstorm results from the conjunction of two
conditions:
• A global shearing of the atmosphere, as wind speed generally increases
with altitude. That wind gradient is enhanced by earth friction, but less by
sea friction
• An airmass of high humidity at lower levels. It is a fact of physics that
humid air is more unstable than dry air. Note that the maximum water
content of an airmass increases very rapidly with temperature.
When those two conditions are met, vertical instability develops. Thunderstorm
activity is enhanced by very small changes in the conditions surrounding the
system:
• A colder airmass arriving at high altitude
• The system passes over an area gradually heated by the sunshine
• Some orographic effect.
Under such conditions, the development of a thunderstorm may be extremely
rapid, even at a visible pace. One may have blue sky in the morning, a severe
thunderstorm in the afternoon and dissipating clouds at sunset, which makes the
weather forecast difficult to interpretate. A thunderstorm often develops up to the
tropopause altitude, sometimes above.
Other characteristics:
• Most thunderstorms have a life cycle associated with the duration of sun
radiation.
• Sea thunderstorms are less severe (less wind gradient and lower surface
temperature).
• Winter thunderstorms often top at altitudes lower than the summer ones
(colder airmass, therefore less water, hence less instability).
As a general rule, aircraft en route should avoid thunderstorms on the
upwind side, if it can be detected.
In a regular atmosphere, the upwind side at the opposite of the anvil. The shape of
the anvil is due to flattening of the cloud and normal wind increase at its altitude.
Under such conditions, the upwind side is free from precipitations and turbulence at
a relatively short distance from the cloud body side. But it may happen that wind
direction changes at the level of the anvil, or the cell is stationary. Under those
conditions, the recommended distance to fly from the cloud must be respected. But
in all cases, avoid flying under the anvil. Severe precipitations, hail, icing, etc may
exist, even at an FL supposed to be under -40°C.
- G-2 -
Getting to grips with Surveillance
Appendix G
G.2.2. SINGLE CELL
A single cell thunderstorm is the result of a single updraft. This kind of
thunderstorms is rare. A single cell may have a life cycle above one hour, because
of its high instability.
G.2.3. MULTI-CELL THUNDERSTORMS
Multi-cell thunderstorms are more common. Each thunderstorm is at different
formation stage. The downdraft of one cell creates a gust front. This gust front
provides the lifting mechanism for new cells. New cells will tend to form on the
downwind side of existing cells.
G.2.4. SUPER CELL
The super cell is an example of
diverging mechanism in atmospheric
dynamics. If the airmass is very
unstable up to a large altitude, vertical
speeds are high. A very active
convection cycle is triggered inside the
cloud, which activates condensation
and icing (step 1 of Figure G - 2). This
puts
dry
air
in
contact
with
precipitations. Dry air is rapidly cooled.
This super cold air is the origin of
massive air falls, called downdraft and
downbursts (step 2 of Figure G - 2).
A super cell thunderstorm can grow up
to 10 NM horizontally and 60 000 ft
vertically. Due to the powerful updraft,
the top of the thunderstorm may
deploy above the Tropopause (step 3 of
Figure G - 2).
Figure G - 2: Super cell development
The resulting anvil top deploys downwind and commonly produces hail. It can
produce powerful updraft (more than 90 kt – 9 100 ft/min), surface winds (more
than 70 kt), large hailstones (10 cm – 4 in), and tornadoes.
G.2.5. OCEANIC CELL
Oceanic cells contain less water than continental cells. Consequently, for
equivalent height, oceanic cells are less massive and less reflective than
continental cells.
G.2.6. SQUALL LINE
A squall line is a line of thunderstorms that form approximately 150 NM ahead of
a cold front. It may extend on several hundred miles. Typical thunderstorm
weather (heavy rain, hail, lightning, strong winds, tornadoes) may occur on a
large area.
- G-3 -
Appendix G
Getting to grips with Surveillance
G.3. HAIL ENCOUNTER
Figure G - 3 provides a rough order of
magnitude of hail encounter probability
with a mature thunderstorm. The
probabilities may vary according to the
current weather conditions.
The thunderstorm is vertically split into
three thirds:
- The top third (ice crystals only) and
the mid third present a high
probability of hail encounter,
-
Figure G - 3: Probability of hail encounter
The bottom third is the area of medium probability.
Hail may also be encountered on the downwind side. This is the reason why
aircraft should avoid thunderstorm on the upwind side.
G.4. TURBULENCE
The present paragraph briefly references the different kind of turbulence.
G.4.1. CLEAR AIR TURBULENCE (CAT)
CATs occur at any altitudes:
- At high altitudes in the shear of jet streams, or
- Any altitudes downstream of mountains, or
- Near areas with high vertical wind gradient.
Weather radars do not detect CATs because CATs do not contain water.
G.4.2. TURBULENCE DOME
Several thousand feet above the visible top of a thunderstorm, severe turbulence
occurs.
G.4.3. THUNDERSTORM VAULT
The thunderstorm vault occurs when the airmass is unstable at high level only and
the lower air is too dry to feed the convection. Most of the unstability is trapped in
the upper part of the thunderstorm. Consequently, there are very little
precipitations. Contrary to a common thunderstorm structure, the bottom part of
the thunderstorm is less reflective than the upper part, or even not visible on
radar display. Refer to Figure 6-27.
G.4.4. DOWNDRAFT
The downdraft is a movement of cool air induced by the precipitation of water
droplets. When the downdraft hits the ground, it spreads out in all directions.
- G-4 -
Getting to grips with Surveillance
Appendix G
If
the
thunderstorm
is
stationary, the resulting gust
front will be more or less
circular, centered on the
downdraft.
If the thunderstorm moves,
the resulting gust front
precedes the thunderstorm:
the gust front is downwind.
Refer to G.4.6 – Gust Front.
Figure G - 4: Downdraft development
G.4.5. DOWNBURST
The downburst is a powerful downdraft that can induce significant damages on the
ground (e.g. felled trees). Horizontal winds from downburst may be as high as
100 kt.
•
•
The macroburst is a downburst on a horizontal extent of more than 4 km.
The microburst is a powerful downburst on a horizontal extent of less than
4 km. It can be either dry or wet:
- A dry microburst occurs with little or no precipitation when reaching
the ground. The dry microburst is the result of an evaporation of rain
in a dry air. The rain that evaporates cools the air. The cool air
descends and accelerates as it approaches the ground. The visible
signs of a dry microburst are:
o A cumulus or cumulonimbus with virga (precipitation that
evaporates before reaching the ground),
o A ring of blowing dust on the ground, beneath the virga.
- A wet microburst occurs with moderate or heavy precipitation on the
ground. The wet microburst forms with the drag of precipitations. The
visible sign of wet microburst is a “rain foot” (prominence of
precipitation) forming near the ground.
G.4.6. GUST FRONT
A gust front is the result of a thunderstorm downdraft hitting the ground and
spreading out on the ground surface. Gust fronts may produce severe turbulence,
and generally spread out downwind.
As a general rule, when flying at low altitude near airports, pay a lot of
care in presence of thunderstorms. The risk of downdraft or downburst is
present all around the cloud, but especially in the direction the cell moves
(approaching thunderstorm). The onset of associated turbulence may be extremely
abrupt. Windshear procedures must be applied without delay. At ground level, the
gust front may appear in a fraction of a second and have enough energy to damage
an aircraft sitting on ground.
- G-5 -
Appendix G
Getting to grips with Surveillance
G.4.7. WIND SHEAR
The wind shear is a variation of wind in speed and/or direction on a short
distance. It is a well-known cause of fatal accidents during take-off or landing.
However, there are several types of wind shears with different levels of danger.
There are several causes for wind shears. The main ones are the following:
• Downburst: It causes the most dangerous wind shear for aircraft as the
wind shear presents a significant wind speed difference, and occurs at low
levels during take-off and landing.
• Wind around obstacles: A steady wind that blows on obstacles (buildings,
mountain ranges, extensive forests, etc) becomes turbulent and induces
wind shears.
• Wind associated with frontal surfaces: When a cold air mass slips
beneath a warmer air mass (clod air is denser than warm air), the contact
of air masses defines the frontal surface. At frontal surfaces, there are wind
velocity discontinuities (i.e. wind shears) due to the dynamics of the frontal
system (different air densities, temperatures, displacement of air masses).
• Front of sea breezes: Sea breeze appears due to the different
temperatures over the land and sea. The front of the sea breeze induces
wind shears when it encounters average surface winds.
• Wake vortices: Wake vortices are a kind of wind shear. They may induce
severe turbulence when the encounter occurs at a certain distance behind
the generating aircraft.
• Radiation inversion and low-level jet streams: At night with fair
weather conditions, the land may cool down faster than the air above.
There is a heat transfer from the warm air to the cool ground. A radiation
inversion occurs: the temperature increases with height. The height of a
radiation inversion is approximately 100 m and goes up to 1 km. Surface
winds tend to be light or calm. When a low level jet stream passes over a
radiation inversion area, wind shears appear.
G.4.8. NON-REFLECTIVE WEATHER
Small cumulus clouds may not content
enough water. Weather radars may not
detect them due to their weak reflectivity.
Nevertheless, this kind of clouds may
produce light to moderate turbulence.
Figure G - 5: Turbulence due to cumulus
The turbulence is due to the alternation of updrafts that form the clouds and
downdrafts between the clouds.
- G-6 -
Getting to grips with Surveillance
Appendix I
APPENDIX H – LOW LEVEL WIND SHEAR EFFECTS ON AIRCRAFT
PERFORMANCES
This appendix provides a summary of wind shear effects on aircraft performances
at low level. For a more detailed analysis of these effects, refer to the ICAO
Manual on Low Level Wind Shear and Turbulence, Doc 9817 (see
References).
H.1. HORIZONTAL WIND SHEARS
There are two kinds of horizontal wind shears: longitudinal wind shears and
crosswind shears. As runways are aligned on dominant winds, the most frequent
wind shears encountered at low levels are longitudinal. Nevertheless, crosswind
shears have some significant effects on the aircraft flight path.
Wind shears affect the aircraft in a transient way. They affect the airspeed, the
altitude, the angle of attack or the drift depending on their direction (longitudinal,
lateral, or vertical). The initial effects of wind shear are the ones that mostly
affect aircraft performances.
H.1.1. LONGITUDINAL WIND SHEARS
Climb
Level
Descent
Figure I - 1: Equilibrium of aerodynamic forces
The equilibrium of aerodynamic forces illustrated in Figure I - 1 assumes that:
- The flight is straight (no turn) and is not accelerating
- The thrust is along the flight path.
γ is the angle of climb/descent.
- G-1 -
Appendix I
Getting to grips with Surveillance
Climb
Level
Descent
Figure I - 2: Resultant flight path vector – Decreasing headwind/Increasing tailwind
Figure I - 2 illustrates the initial effect (resultant flight path vector R) due to the
transient decrease of airspeed following a decreasing headwind or an increasing
tailwind, until the aircraft reaches a new equilibrium.
Figure I - 3: Resultant flight path vector – Increasing headwind/Decreasing tailwind
Figure I - 3 illustrates the initial effect (resultant flight path vector R) due to the
transient increase of airspeed following an increasing headwind or a decreasing
tailwind, until the aircraft reaches a new equilibrium.
Considering the transient effect of wind shears on airspeed, an increasing
headwind is equivalent to a decreasing tailwind, and vice-versa.
When the aircraft passes the wind shear, the aircraft naturally returns to
equilibrium thanks to its longitudinal stability. However, the flight crew must often
take the controls to avoid the aircraft starting phugoid oscillations (airspeed and
height oscillations with a period of approximately 40 seconds).
Figure I - 4 illustrates the effects of longitudinal wind shears on the flight path at
take-off and landing.
H.1.2. CROSSWIND SHEARS
The initial effect of a crosswind shear affects the drift and the sideslip angles,
without any initial effects about airspeed and altitude. When the aircraft
encounters a crosswind shear, the aircraft:
- Yaws towards the shear
- Rolls away from the shear
- Drifts away from the nominal flight path (see Figure I - 5).
- G-2 -
Getting to grips with Surveillance
Appendix I
Landing
Take-off
Figure I - 4: Effects of longitudinal wind shears on flight path
Figure I - 5: Effect of crosswind shears on flight path
H.2. VERTICAL WIND SHEARS
H.2.1. EFFECT ON ANGLE OF ATTACK
Figure I - 6: Wing aerofoil view –
Vertical wind shear effect
In a level flight, the airflow hits the
wing horizontally. When the aircraft
flies in a downdraft or updraft, the
resultant airflow (i.e. nominal airflow +
downdraft/updraft) hits the wing with
an angle to the horizontal. This angle
depends of the airspeed and the
velocity of the downdraft or updraft.
The pitch attitude remains unchanged.
- G-3 -
Appendix I
Getting to grips with Surveillance
The initial effect of a downdraft is then a transient reduction of the Angle Of
Attack (AOA) that leads to a transient lift reduction. On the contrary, the initial
effect of an updraft is a transient increase of the AOA that leads to a transient lift
increase.
As a consequence, the initial effect of a downdraft on the flight path is the same
as the one with a decreasing headwind or increasing tailwind (see Figure I - 4).
And the initial effect of an updraft is the same as the one with an increasing
headwind or decreasing tailwind.
When the aircraft passes the vertical wind shear, the aircraft naturally returns to
equilibrium thanks to its longitudinal stability. Without any pilot actions, pitch
oscillations may occur with a period of approximately 5 seconds.
H.2.2. DOWNBURST EFFECTS
A downburst is a powerful downdraft produced by a thunderstorm. As it
approaches the ground, the downburst splits in all directions.
Figure I - 7: Downburst effect
Figure I - 8: Downburst side view
Figure I - 7 and Figure I - 8 illustrate the effects of downburst on the flight path
assuming that the downburst is centered on the glide path. Effects of vertical wind
shears on AOA and of longitudinal wind shears are combined.
When the downburst is centered on the glide path, the effects of the
downburst are sequenced in three steps:
1. The aircraft encounters an increasing headwind. The aircraft flies above the
glide path (See Figure I - 4).
2. The aircraft comes into the center of the downburst and encounters a
vertical wind shear. In a downburst, the AOA and then the lift are reduced.
The aircraft passes below the glide path (See Figure I - 4).
3. The aircraft encounters an increasing tailwind. The lift increases; the
aircraft may regain or overshoot the glide path according to the magnitude
of the tailwind (See Figure I - 4).
- G-4 -
Getting to grips with Surveillance
Appendix I
A downburst centered on the glide path is the worst wind shear case when
approaching the runway. Indeed, the aircraft encounters wind shears in opposite
directions along the flight path plus a downdraft.
When the downburst is not centered on the glide path, the aircraft encounters less
critical but non-negligible effects: airspeed, drift, and descent rate vary. See
situations 1 and 2 of Figure I - 9.
Figure I - 9: Downburst effect – Top view
Effects
Airspeed
Drift
Descent rate
Airspeed
Drift
Descent rate
Airspeed
Drift
Descent rate
Downburst Position vs. Aircraft
Increasing
Increasing Left
Decreasing
Increasing
N/A
Decreasing
Increasing
Increasing Right
Decreasing
Increasing Left
Increasing Right
- G-5 -
Decreasing
Decreasing Left
Increasing
Decreasing
N/A
Increasing
Decreasing
Decreasing Right
Increasing
Situation
1
2
3
Flight Operations Support & Services
AIRBUS S.A.S.
31707 BLAGNAC CEDEX, FRANCE
CONCEPT DESIGN GDB
MAY 2009
PRINTED IN FRANCE
© AIRBUS S.A.S. 2009
ALL RIGHTS RESERVED
AIRBUS, ITS LOGO, A300, A310, A318,
A319, A320, A321, A330, A340, A350, A380,
A400M ARE REGISTERED TRADEMARKS
getting to grips with
Proprietary document.
By taking delivery of this Brochure (hereafter “Brochure”), you
accept on behalf of your company to comply with the following: .No
other property rights are granted by the delivery of this Brochure
than the right to read it, for the sole purpose of information. This
Brochure, its content, illustrations and photos shall not be modified
nor reproduced without prior written consent of Airbus S.A.S. This
Brochure and the materials it contains shall not, in whole or in part,
be sold, rented, or licensed to any third party subject to payment or
not. This Brochure may contain market-sensitive or other information that is correct at the time of going to press. This information
involves a number of factors which could change over time, affecting the true public representation. Airbus assumes no obligation to
update any information contained in this document or with respect
to the information described herein. The statements made herein do
not constitute an offer or form part of any contract. They are based
on Airbus information and are expressed in good faith but no warranty or representation is given as to their accuracy. When additional information is required, Airbus S.A.S can be contacted to provide
further details. Airbus S.A.S shall assume no liability for any damage in connection with the use of this Brochure and the materials it
contains, even if Airbus S.A.S has been advised of the likelihood of
such damages. This licence is governed by French law and exclusive jurisdiction is given to the courts and tribunals of Toulouse
(France) without prejudice to the right of Airbus to bring proceedings
for infringement of copyright or any other intellectual property right
in any other court of competent jurisdiction.
surveillance
Issue I - May 2009
Was this manual useful for you? yes no
Thank you for your participation!

* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project

Download PDF

advertisement