FLT_OPS-TOFF_DEP
Flight Operations Briefing Notes
Takeoff and Departure Operations
Response to Stall Warning Activation at Takeoff
Flight Operations Briefing Notes
Takeoff and Departure Operations
Response to Stall Warning Activation at Takeoff
I
Introduction
This Flight Operations Briefing Note provides an overview of:
•
The operational guidelines to follow in response to a stall warning at takeoff,
for an improved understanding of recovery techniques
•
The factors that lead to stall warning activation at takeoff, and
•
The corresponding prevention strategies.
Flight crew situational awareness, in the event of a stall warning, is essential to
the successful application of recovery techniques. This is particularly true for aircraft
that do not have full protection throughout the flight envelope. This heightened
awareness is principally necessary at takeoff, when the risk of ground contact exists.
Note:
This Flight Operations Briefing Note is primarily designed for aircraft that do not have
flight envelope protection (e.g. A300/A310/A300-600).
However, the key points at the end of this briefing note are also applicable to all aircraft
types, with or without flight envelope protection. For this reason, all pilots are invited to
read this document.
Page 1 of 8
Flight Operations Briefing Notes
II
Takeoff and Departure Operations
Response to Stall Warning Activation at Takeoff
Background Information
II.1 Stall Warning Definition
Airworthiness regulations require three levels of protection against stall:
•
Adequate speed margin (minimum speed vs. Vstall)
•
Unmistakable recognition of stall qualities (natural or artificial) prior to the real stall
•
Acceptable aircraft behavior when stalled (e.g. max bank angle).
Nowadays, if a stall is impending, most aircraft are equipped with such artificial stall
warning, as audio alerts (cricket sound) and tactile alerts (stick shaker effect).
A stall warning triggers when the aircraft’s Angle-Of-Attack
a predetermined value: This value depends on the slat configuration.
(AOA)
exceeds
The warning indicates the proximity of the aircraft’s AOA compared to the stall’s AOA
(Figure 1).
Figure 1
Lift at given Angle-of-Attack
The stall warning is inhibited on ground, until liftoff.
II.2 Operational Consequences
When an aircraft is airborne, stall warning activation can be catastrophic, if the flight
crew does not respond correctly and effectively.
Worldwide experience records events where flight crews have been misled by
a spurious / untimely stall warning activation at liftoff. Some of them have resulted in
fatal accidents (e.g.: rejected takeoff after rotation, CFIT).
Page 2 of 8
Flight Operations Briefing Notes
III
Takeoff and Departure Operations
Response to Stall Warning Activation at Takeoff
Applicable Standards / Techniques
If a stall warning triggers at a low altitude, the flight crew should consider that there is
an immediate flight path threat, and a potential risk of ground contact.
In other words, there is no time to differentiate between a real or spurious stall
warning, and there is no altitude to convert to speed.
However, when a stall warning triggers (i.e. stick shaker activation), aircraft still have
positive climb performance capability.
Note:
An “approach to stall” is a controlled flight maneuver. An aircraft that is stalled is out of
control, but is recoverable. Do not confuse an “approach to stall” with “a full stall”.
When ground clearance is not an issue, the recommended technique is to recover from
the near-stall condition in the minimum amount of time, by applying power and nose
down input.
When ground clearance is an issue, the recommended technique is to lose as little
altitude as possible, by applying full power and by flying an optimum pitch attitude.
This optimum pitch attitude depends on the aircraft’s proximity to the ground:
•
At Liftoff:
At liftoff, an optimum pitch attitude of 12.5 degrees is required.
This pitch attitude is necessary to avoid the risk of ground contact, and ensures an
increase in speed, regardless of the aircraft’s takeoff weight, center of gravity, type
(i.e. A300/A310/A300-600), actual slats and flaps configuration, or if there is an
engine failure.
•
After Liftoff:
The optimum pitch attitude is a reduced pitch. However, this reduction is no more
than necessary to enable the airspeed to increase while there is a risk of ground
contact.
Note:
The “Procedures and Techniques” section of the A300/A310/A300-600 FCOMs provides
the complete recovery procedure to be applied in the event of a stall warning
activation.
An analogy can be made with the guidelines that are provided during flight crew
training to be applied in the event of an engine failure:
−
Immediate procedure for aircraft control, then
−
Performance management.
Page 3 of 8
Flight Operations Briefing Notes
IV
Takeoff and Departure Operations
Response to Stall Warning Activation at Takeoff
Operational and Human Factors involved in Stall Warning Activation
at Takeoff
At takeoff, stall warnings are the result of one, or a combination, of the following
factors:
•
•
•
•
V
Weather Factors:
−
Icing conditions
−
Windshear.
Human Factors:
−
Insufficient aircraft de-icing in cold weather operations
−
Incorrect loading (e.g. cargo not positioned in accordance with the load and trim
sheet, …)
−
Incorrect slats/flaps configuration
−
Incorrect takeoff speed.
Flight Crew Techniques:
−
Early rotation below the specified speed, resulting in a higher peak AOA
−
Maneuvering near the minimum speed at an excessive bank angle
−
Premature retraction of the flaps.
Aircraft Systems:
−
Engine failure and subsequent loss of energy
−
Malfunction of artificial stall warning, leading to spurious stall warnings, caused
by a damaged AOA probe, by an AOA probe that is not correctly rigged, or by
a computer failure.
Prevention Strategies / Lines of Defense
The flight crew should pay special attention to the following prevention strategies and
“lines of defense”:
•
Concentrate on taking action early enough to prevent the occurrence of a stall
warning
•
Learn how to recognize an “approach to stall”
•
During recurrent training, reinforce and confirm the correct flight crew response to
a stall warning activation at takeoff.
Page 4 of 8
Flight Operations Briefing Notes
Takeoff and Departure Operations
Response to Stall Warning Activation at Takeoff
V.1 Cockpit Preparation – Takeoff Briefing
The Takeoff Briefing should address the following:
•
Clean Aircraft Concept
In conditions that are conducive to aircraft icing, the preflight briefing must
emphasize the “clean aircraft concept”. This concept requires knowledge of:
−
The adverse effects that ice, frost, or snow can have on aircraft performance
and on its handling qualities
−
The various ground anti-icing and de-icing procedures, as well as their
limitations
−
The necessity to perform walkaround inspections, in order to check for ice
accumulation on lifting surfaces.
Note:
Airbus brochure “Getting to Grips with Cold Weather Operations” provides additional
information concerning the “clean aircraft concept” .
•
Windshear Awareness
Flight crews should consider all available windshear-awareness items (Refer to the
Flight Operations Briefing Note Windshear Awareness), assess the conditions for
a safe takeoff, and delay takeoff until conditions improve, as warranted.
•
Performance Computation
Flight crews should determine the correct performance and takeoff speeds,
depending on the prevailing conditions, and they should select the appropriate
configuration, power settings, and speeds (Refer to the Flight Operations Briefing
Notes Understanding Takeoff Speeds and Conducting Effective Briefings).
V.2 Flying Techniques
During the takeoff roll, the Pilot-Not-Flying (PNF) should be aware of V-speeds, and is
responsible for calling out a timely “rotate” at VR.
On this callout, the Pilot-Flying (PF) should adhere to the standard rotation technique,
then follow the FD bars after liftoff.
When the aircraft is above the acceleration altitude, and accelerates above
the minimum speed associated with the next configuration (i.e. when there is a positive
speed trend on the PFD), the PF should call for slats/flaps retraction. Before initiating
the retraction, the PNF should confirm that this condition has been checked.
Page 5 of 8
Flight Operations Briefing Notes
Takeoff and Departure Operations
Response to Stall Warning Activation at Takeoff
V.3 Approach to Stall Recognition
The following information should be a part of basic aeronautics:
•
Stall Speed Awareness
The stall speeds that are published in the Aircraft Flight Manual (AFM) have been
defined for specific conditions (e.g. wings level, normal load factor near 1.0). In
other conditions (e.g. excessive bank angle), the stall may occur above the
published stall speed.
Flying at the minimum speed (e.g. V2) provides a margin with respect to stall, as
required by the regulation. However, this margin is reduced when the aircraft is
flying under g loads that are greater than 1 g.
The stick shaker and the stall warning trigger, when the AOA reaches a
predetermined value. Therefore, the effect of the load factor is considered to trigger
the warning.
Maneuvering near the minimum speed with an excessive bank angle may therefore
lead to a real stall warning activation.
•
Stall Warning Cues at Takeoff
As indicated, timely recognition of an ”approach to stall” is vital to the successful
implementation of the recovery procedure.
The following alertness factors should be monitored:
−
The speed goes below V2
−
The speed symbol on the PFD speed scale (depending on the aircraft type) goes
below the stick shaker speed displayed as a red and black strip (Figure 2)
−
The vertical speed does not increase as expected.
Figure 2
Red and Black Strip Displayed on PFD (e.g. A310/A300-600)
Page 6 of 8
Flight Operations Briefing Notes
Takeoff and Departure Operations
Response to Stall Warning Activation at Takeoff
In all stall warning cases, there is a tactile alert (i.e. stick shaker activation) and
an aural alert so that the flight crew can feel, and hear the stall warning with enough
opportunity to quickly recover aircraft.
V.4 Training Program Outline
The recurrent training program should include a Full Flight Simulator session that takes
into account the activation of a stall warning at takeoff. The purpose of such
a simulator exercise is for the flight crew to observe and to practice the correct
response to stall warning activation at takeoff.
This exercise, proposed in the Airbus standard recurrent training course, should be
performed every 3 years.
In addition to the training documentation, the Procedures and Techniques section of
the A300/A300-600/A310 FCOM should be used in association with this Flight
Operations Briefing Note, as briefing material.
VI
Summary of Key Points
Recurrent training for all aircraft types should highlight the following key points, when
addressing stall warning awareness and flight crew response to a stall warning
activation at takeoff:
VII
•
Preventive actions must (ideally) be taken before the stall warning
•
At low altitudes, there is no time to distinguish between a real or spurious stall
warning, and there is no altitude to convert to speed
•
The PF’s response must be immediate:
Fly optimum
(e.g. 12.5 degrees at liftoff) and use maximum allowable thrust
•
The recovery maneuver must be continued, until a safe flight path and speed are
achieved and maintained.
Associated Flight Operations Briefing Notes
The following Flight Operations Briefing Notes can also be reviewed:
•
Understanding Takeoff Speeds
•
Conducting Effective Briefings
•
Standard Calls
•
Windshear Awareness
Page 7 of 8
pitch
attitude
Flight Operations Briefing Notes
VIII
IX
Takeoff and Departure Operations
Response to Stall Warning Activation at Takeoff
Airbus References
•
A300/A310/A300-600 Flight Crew Operating Manual (FCOM) - Procedures and
Techniques - Recovery from Stall Warning
•
A310/A300-600 Flight Crew Training Program (FCTP) – Abnormal Operation
Briefings – Flight Controls – Recovery from Approach to Stall
•
Airbus Brochure: “Getting to Grips with Cold Weather Operations”
•
Airbus Brochure: “Getting to Grips with Aircraft Performance”
•
Airbus Brochure: “Getting to Grips with Aircraft Weight and Balance”.
Additional Reading Materials
The following publications also address events that illustrate this Briefing Note:
•
Flight Safety Foundation – Publications - Accident Prevention August 1993
•
Flight Safety Foundation – Publications - Accident Prevention July 1998
•
Flight Safety Foundation – Publications - Accident Prevention July 2004.
Note:
These Flight Safety Foundation publications can be found on the Flight Safety
Foundation website http://www.flightsafety.org/ap_home.html.
This FOBN is part of a set of Flight Operations Briefing Notes that provide an overview of the applicable standards, flying
techniques and best practices, operational and human factors, suggested company prevention strategies and personal linesof-defense related to major threats and hazards to flight operations safety.
This FOBN is intended to enhance the reader's flight safety awareness but it shall not supersede the applicable regulations
and the Airbus or airline's operational documentation; should any deviation appear between this FOBN and the Airbus or
airline’s AFM / (M)MEL / FCOM / QRH / FCTM, the latter shall prevail at all times.
In the interest of aviation safety, this FOBN may be reproduced in whole or in part - in all media - or translated; any use of
this FOBN shall not modify its contents or alter an excerpt from its original context. Any commercial use is strictly excluded.
All uses shall credit Airbus.
Airbus shall have no liability or responsibility for the use of this FOBN, the correctness of the duplication, adaptation or
translation and for the updating and revision of any duplicated version.
Airbus Customer Services
Flight Operations Support and Services
1 Rond Point Maurice Bellonte - 31707 BLAGNAC CEDEX FRANCE
FOBN Reference : FLT_OPS – TOFF_DEP – SEQ 08 – REV 01 – APR. 2005
Page 8 of 8
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