SkyView Autopilot In-Flight Tuning Guide

SkyView
Autopilot In-Flight Tuning Guide
This product is not approved for installation in type certificated aircraft
Document 102064-000, Revision B
For use with firmware version 10.0
March, 2014
Copyright © 2009-2014 by Dynon Avionics, Inc.
Permission to print this this manual is granted to third parties
Table of Contents
Copyright
2008-2014 Dynon Avionics, Inc. All rights reserved. No part of this manual may be reproduced, copied, transmitted, disseminated or stored in any storage
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Information in this document is subject to change without notice. Dynon Avionics reserves the right to change or improve its products and to make changes in the
content without obligation to notify any person or organization of such changes. Visit the Dynon Avionics website (www.dynonavionics.com) for current updates
and supplemental information concerning the use and operation of this and other Dynon Avionics products.
Revision History
Revision
A
Revision Date
June 2013
B
March 2014
Description
Initial release
Updated for SkyView v10.0:
- Added BANK ANGLE LIMIT
- Mention of SV-AP-PANEL only active in EXPERT mode
Table 1–SkyView Autopilot In-Flight Tuning Guide Revision History
Table of Contents
Copyright ....................................................................................................................................................................... ii
Revision History ............................................................................................................................................................. ii
1. Overview
1-1
Purpose .......................................................................................................................................................................1-1
Things to Look For ......................................................................................................................................................1-2
Resetting Autopilot Defaults ......................................................................................................................................1-2
2. Flight Test Preparation
2-1
Overview .....................................................................................................................................................................2-1
Disconnecting the Autopilot .......................................................................................................................................2-1
Accessing Autopilot Setup ..........................................................................................................................................2-1
3. Roll Axis – TRK and Turns Procedure
3-1
Overview .....................................................................................................................................................................3-1
Flowchart ....................................................................................................................................................................3-2
BANK ANGLE LIMIT .....................................................................................................................................................3-3
4. Pitch Axis – IAS Hold Procedure
4-1
Overview .....................................................................................................................................................................4-1
Flowchart ....................................................................................................................................................................4-2
5. Pitch Axis – Altitude Hold and Capture Procedure
5-1
Overview .....................................................................................................................................................................5-1
Flowchart ....................................................................................................................................................................5-2
6. Turbulence Tuning Procedure
6-1
Overview .....................................................................................................................................................................6-1
Flowchart ....................................................................................................................................................................6-2
SkyView Autopilot In-Flight Tuning Guide - Revision B
ii
Table of Contents
7. Roll Troubleshooting
7-1
Roll Troubleshooting Procedure .................................................................................................................................7-1
Roll Performance Troubleshooting Procedure ...........................................................................................................7-2
Appendix A: Autopilot Settings –Defaults
SkyView Installation Guide
8-1
iii
1. Overview
Purpose
The goal of the AP tuning procedure is to maximize the performance of the Autopilot in your
aircraft. The steps described accomplish this systematically and reduce guesswork, so follow
them carefully.
All procedures in this guide should be exercised regardless of how the autopilot is intended to
be used in the aircraft. In particular, if you are using the vertical navigation features of the
autopilot, pay special attention to the IAS Hold tuning procedure. Tuning this well will give the
best results when using vertical guidance.
Once IAS hold is well tuned, the AP will be able to get the best performance during normal
climbs and descents in either expert or simplified modes, and the altitude capture and hold
procedure should be used to finalize vertical performance.
Once you have configured the autopilot to capture and hold airspeeds and altitudes, you may
wish to adjust the ride quality in turbulence, particularly on the glideslope.
Similarly, the Roll Axis TRK and Turns Procedure will ensure best performance both in normal
turns and when following lateral guidance on approaches.
It is critical that once tuned, you familiarize yourself with AP procedures, and verify
the performance of the autopilot on approaches in VMC before use in IMC.
Performance of the AP is degraded by excessive servo slippage. If during
verification of approach performance you find that the servo is slipping, verify that
you have the torque set to the maximum value, and if slips continue, contact Dynon
for advice on servo sizing.
HDG mode performance is only as good as your compass calibration. If you have
concerns about your compass, refer to the compass calibration guide in the
SkyView System Installation Guide.
The SV-AP-PANEL is enabled when AP CONTROLS are set to EXPERT mode. For
tuning procedures performed in SIMPLIFIED mode, the buttons on the SV-AP-PANEL
will not be active.
SkyView Autopilot In-Flight Tuning Guide - Revision B
1-1
Overview
Things to Look For
Most autopilot problems come down to two things: SLIP and SLOP. Be alert for the SLIP
/
indication on either axis. While either SLIP indications are being
displayed NOBODY IS FLYING THE AIRPLANE. Resolve SLIP issues on either axis before
proceeding, either by increasing torque, switching to a larger servo, or contacting Dynon for
service.
Lost motion (SLOP) between the servo and the control surface will have a negative impact on
performance. Verify that the control surface cannot move more than one degree (total motion)
while the servo is holding position.
The Flight Director provides a valuable tool for evaluating the performance of the AP. If the
autopilot is not able to keep up with Flight Director command bars, sensitivity should be
increased. If the autopilot can keep up, but gets a late start and lags behind the flight director,
PITCH GAIN or ROLL GAIN can be used to speed up response. Use sparingly! Excessive PITCH
GAIN and ROLL GAIN can result in rough performance.
Resetting Autopilot Defaults
A final note on tuning the autopilot: Less is more. Before changing any settings, try each
procedure and determine if performance is acceptable as-is; often you will have to make only
minor changes. If you find that you’ve turned all the settings all the way up, you’ve probably
gone too far. Stop and review the procedures, and then go back to the defaults and re-evaluate
performance.
If you feel you need to reset the settings in the Autopilot Settings menu back to their defaults,
see Appendix A: Autopilot Settings –Defaults for the default values.
1-2
SkyView Autopilot In-Flight Tuning Guide - Revision B
2. Flight Test Preparation
Overview
The flight test should be conducted on a clear, VFR day. Before commencing the flight test,
ensure that you have adequate altitude, clear weather, no traffic, no obstructions in the flight
path, great visibility, no airspace conflicts, etc. It is recommended that clearing turns be
performed before executing each procedure.
It is highly recommended that you bring someone along on the first autopilot test
flight. At many points, the pilot’s attention will be divided between documentation,
configuring SkyView, and maintaining situational awareness.
Disconnecting the Autopilot
If autopilot behavior, performance, or interference with the controls is cause for concern while
flying, remember that the autopilot can be disconnected the following ways:





Press the Autopilot servo Disconnect button
Within the Simplified AP Controls: Press the OFF button
Within the Expert AP Controls: Press the AP button
On the SV-AP-PANEL Autopilot Control Panel, push the AP button
(if SV-AP-PANEL is enabled – AUTOPILOT CONTROL set to EXPERT)
Pull the autopilot circuit breaker or remove the autopilot fuse
Accessing Autopilot Setup
In the following instructions, the setup menus for Autopilot tuning are accessed by
Pushing Buttons 7+8
Then, select AUTOPILOT SETUP (and click the knob to the right, once). You will then be in
AUTOPILOT SETUP.
SkyView Autopilot In-Flight Tuning Guide - Revision B
2-1
3. Roll Axis – TRK and Turns Procedure
Overview
This procedure tunes the roll autopilot servo and thus, the flight characteristics of the aircraft in
heading holds and turns. This procedure should be performed with the autopilot roll axis in
track (TRK+ALT) mode, where the purpose of the autopilot is to keep the aircraft’s GPS ground
track aligned with the track bug (as well as hold altitude). Before executing this procedure:
The autopilot controls should be changed to SIMPLIFIED mode
(SETUP MENU > AUTOPILOT SETUP > AUTOPILOT CONTROLS)
The Roll Axis tuning process can be summarized as follows:
Change TRK command by approximately 90 degrees, and observe the results. The AP should
promptly roll into a turn towards the new TRK and smoothly reach the commanded TRK with
little or no overshoot.
Note: be sure to observe ground track (TRK) and not heading (HDG) during this
procedure.
If the AP is slow to respond to the TRK changes, increase the ROLL AXIS SENTIVITY and watch
for improvement. In some cases this may require a fair amount of increase, but be cautious
about changing it too quickly. Sensitivity adjustments alone may not completely eliminate
overshoot. If increasing sensitivity no longer improves performance, ROLL GAIN may be used to
fine tune the roll axis. Too much sensitivity may cause AP responses to be “twitchy”. Reduce
ROLL SENSITIVITY if this occurs. Too much ROLL GAIN will result in a rough ride.
In particular, if the autopilot cannot keep up with the flight director roll command bar, ROLL
SENSITIVITY should be increased. At some point the AP will track the command bars, but follow
behind them. ROLL GAIN will reduce the gap.
Caution: Large changes in ROLL SENSITIVITY with the autopilot engaged can result
in large servo movements.
SkyView Autopilot In-Flight Tuning Guide - Revision B
3-1
Roll Axis – TRK and Turns Procedure
Flowchart
Figure 1 – Roll Axis – TRK and Turns Procedure
3-2
SkyView Autopilot In-Flight Tuning Guide - Revision B
BANK ANGLE LIMIT
After Roll Axis tuning is complete, BANK ANGLE LIMIT should be set to a value that results in a
bank angle in AP that is comfortable for your plane and your preferences. A place to start is to
set BANK ANGLE LIMIT to a value that yields a standard rate turn at typical cruise speed.
The default BANK ANGLE LIMIT is 30°.
The SkyView AP will always obey BANK ANGLE LIMIT. However, if BANK ANGLE
LIMIT is set too low (such as 5°), the SkyView AP will be unable to turn.
SkyView Installation Guide
3-3
4. Pitch Axis – IAS Hold Procedure
Overview
The goal of tuning IAS Hold is to give the AP the best possible pitch axis performance. Crisp
speed control is a prerequisite for good altitude and glideslope control. Although IAS hold is
only available in EXPERT mode, tuning will benefit SIMPLIFIED mode greatly, so even if you
don't intend to use EXPERT mode, this procedure is essential for good performance.
The procedure which follows can be used both for initial tuning and for troubleshooting
problems which may arise in your system. Like any checklist or procedure, be sure to follow
each step.
The autopilot controls should be changed to EXPERT mode
(SETUP MENU > AUTOPILOT SETUP > AUTOPILOT CONTROLS)
The ALT bug should be set to an altitude many thousands of feet above or below
the intended flight testing altitude. This is to keep the autopilot in IAS Hold mode
throughout the procedure, and prevent the autopilot from capturing the target
altitude.
The Pitch Axis IAS Hold tuning process can be summarized as follows:
Increase or decrease airspeed command by 10 knots, and observe the results. The AP should
promptly change pitch to change speed, and smoothly reach the commanded speed with little
or no overshoot (above the target if increasing; below the target if decreasing).
If the AP is slow to respond to the airspeed changes, increase the PITCH SENSITIVITY and watch
for improvement. In some cases this may require a fair amount of increase, but be cautious
about changing too quickly. Sensitivity adjustments alone may not completely eliminate
overshoot. If increasing sensitivity no longer improves performance, PITCH GAIN may be used
to fine tune IAS Hold. Too much sensitivity may cause AP responses to be "twitchy". Reduce
PITCH SENSITIVITY if this occurs. Too much PITCH GAIN will result in a rough ride.
In particular, if the autopilot cannot keep up with the flight director pitch command bar, PITCH
SENSITIVITY should be increased. At some point the AP will track the command bars, but follow
behind them. PITCH GAIN will reduce the gap.
Caution: Large changes in PITCH SENSITIVITY with the autopilot engaged can result
in large servo movements.
SkyView Autopilot In-Flight Tuning Guide - Revision B
4-1
Pitch Axis – IAS Hold Procedure
Flowchart
Figure 2 – Pitch Axis – IAS Hold Procedure
4-2
SkyView Autopilot In-Flight Tuning Guide - Revision B
5. Pitch Axis – Altitude Hold and Capture Procedure
Overview
Both holding and capturing altitude are related but distinct parts of the autopilot. The Altitude
Hold Procedure which follows will address common problems, and once those are resolved,
direct you to the Altitude Capture Procedure, which will tune your system to capture and hold
vertical speed and capture altitude targets without overshoot.
You must complete the IAS HOLD tuning procedure before performing this
procedure.
The autopilot controls should be changed to SIMPLIFIED mode
(SETUP MENU > AUTOPILOT SETUP > AUTOPILOT CONTROLS)
SkyView Autopilot In-Flight Tuning Guide - Revision B
5-1
Pitch Axis – Altitude Hold and Capture Procedure
Flowchart
Figure 3 – Pitch Axis – Altitude Hold Procedure
5-2
SkyView Autopilot In-Flight Tuning Guide - Revision B
Pitch Axis – Altitude Hold and Capture Procedure
Figure 4 – Altitude Capture Procedure (Part 1 of 2)
SkyView Installation Guide
5-3
Pitch Axis – Altitude Hold and Capture Procedure
Figure 5 – Altitude Capture Procedure (Part 2 of 2)
5-4
SkyView Autopilot In-Flight Tuning Guide - Revision B
6. Turbulence Tuning Procedure
Overview
Once you have configured your autopilot to capture and hold airspeeds and altitudes, you may
wish to adjust the ride quality in turbulence, particularly on the glideslope.
In general, the autopilot will attempt to maintain a constant G-loading through bumps by
pulling or pushing G to oppose G generated by "air pockets". The amount of G the autopilot will
apply is limited by G ERROR LIMIT. If, for example, you encounter a 0.5 G updraft, and G ERROR
LIMIT is set to 0.25, the most the AP can do to attenuate the bump is reduce it by 0.25 G.
The amount the autopilot will apply up to that limit is determined by G ERROR GAIN. If this is
set to 1, for every 1/10 G the airplane is bumped, the AP will apply 1/10 of a G. Increasing G
ERROR GAIN will make response more rapid, but also more abrupt, so use this setting with care.
SkyView Autopilot In-Flight Tuning Guide - Revision B
6-1
Turbulence Tuning Procedure
Flowchart
Figure 6 – Turbulence Tuning Procedure
6-2
SkyView Autopilot In-Flight Tuning Guide - Revision B
7. Roll Troubleshooting
Roll Troubleshooting Procedure
Figure 7 – Roll Axis – Roll Troubleshooting Procedure
SkyView Autopilot In-Flight Tuning Guide - Revision B
7-1
Roll Troubleshooting
Roll Performance Troubleshooting Procedure
Figure 8 – Roll Axis – Roll Performance Troubleshooting Procedure
7-2
SkyView Autopilot In-Flight Tuning Guide - Revision B
Appendix A: Autopilot Settings –Defaults
ROLL Axis Setting
Minimum
Maximum
Default
10%
100%
100%
SENSITIVITY
1
24
10
ROLL GAIN
0.0
5.0
0.0
5
45
30
Minimum
Maximum
Default
10%
100%
100%
SENSITIVITY
1
24
10
PITCH GAIN
0.1
3.0
2.0
ALTITUDE GAIN
0.1
2.5
0.6
PULL RATE
1.0
2.0
1.0
VSI GAIN
0.10
2.50
0.6
G ERROR GAIN
0.0
4.0
1.0
G ERROR LIMIT
0.10
1.00
0.25
DEFAULT CLIMB VERT SPD
100 ft/min
3000 ft/min
500 ft/min
DEFAULT DESCENT VERT SPD
100 ft/min
3000 ft/min
500 ft/min
MAXIMUM AIRSPEED
1.30 * Vs1
0.95 * Vne
0.95 * Vne
MINIMUM AIRSPEED
1.30 * Vs1
0.95 * Vne
1.30 * Vs1
TORQUE
BANK ANGLE LIMIT
PITCH Axis Setting
TORQUE
SkyView Autopilot In-Flight Tuning Guide - Revision B
8-1