Flight Test Results of Direct-Measure and Derived Angle-Of-Attack Systems for General Aviation ...

110 Pages·2017·4.36 MB·English

DOT/FAA/TC-16/52 Flight Test Results of Direct-
Federal Aviation Administration
William J. Hughes Technical Center
Measure and Derived Angle-of-
Aviation Research Division
Atlantic City International Airport
New Jersey 08405 Attack Systems for

General Aviation Airplanes

November 2017

Final Report

This document is available to the U.S. public
through the National Technical Information
Services (NTIS), Springfield, Virginia 22161.

This document is also available from the
Federal Aviation Administration William J. Hughes
Technical Center at actlibrary.tc.faa.gov.

U.S. Department of Transportation
Federal Aviation Administration
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Consult the FAA sponsoring organization listed on the Technical
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Technical Report Documentation Page
1. Report No. 2. Government Accession No. 3. Recipient's Catalog No.

DOT/FAA/TC-16/52

4. Title and Subtitle 5. Report Date

FLIGHT TEST RESULTS OF DIRECT-MEASURE AND DERIVED ANGLE-OF- November 2017
ATTACK SYSTEMS FOR GENERAL AVIATION AIRPLANES 6. Performing Organization Code

541330
7. Author(s) 8. Performing Organization Report No.

E. Bruce Jackson and Keith D. Hoffler
9. Performing Organization Name and Address 10. Work Unit No. (TRAIS)

Adaptive Aerospace Group, Inc.
100 Exploration Way, Suite 330
Hampton, VA 23666
11. Contract or Grant No.

DTFACT-15-C-00005
12. Sponsoring Agency Name and Address 13. Type of Report and Period Covered

U.S. Department of Transportation Final Report
Federal Aviation Administration March 2015–February 2016
FAA Central Regional Office
901 Locust St 14. Sponsoring Agency Code
Kansas City, MO 64106 AIR-714

15. Supplementary Notes

The FAA William J. Hughes Technical Center Aviation Research Division COR was Robert J. McGuire.
16. Abstract

Two commercial off-the-shelf angle of attack (AoA) systems were evaluated in flight against a calibrated AoA probe in an
instrumented Cessna R182. One of the systems used a direct-measuring sensor that was mounted in the flow field. This is referred
to as “sensed AoA.” The other system consisted of an algorithm to derive AoA from a commercial attitude and heading reference
unit (hence the term “derived AoA”). In addition, a novel derived AoA estimation algorithm was developed and tested in both
ground simulation and in post-processing of actual flight test data for a variety of stalls.

Some effort was required to obtain satisfactory results from the sensed AoA commercial system, including relocation of the sensor.
Following relocation, the sensed AoA system worked well, as did the derived AoA system using a commercially developed
algorithm and Attitude and Heading Reference System unit.

The novel derived AoA algorithm used parameters available from a certified electronic flight information system. It also relied on
estimates of key aerodynamic parameters, such as the lift slope coefficient, obtained through in-flight calibrations at different flap
and landing-gear configurations. It also required readily available aircraft information (e.g., weight, surface area, and sensor
location). This approach shows promise, but additional work is required to make it commercially feasible, including reducing the
number of input signals required and simplification of the calibration procedure. A study of the sensitivity of the algorithm indicated
which inputs are important for good AoA estimation and suggests other inputs that could be approximated.

Testing of the novel algorithm showed good comparisons with calibrated AoA to near-stall conditions, where output signal limiting
of the calibrated AoA probe led to poor comparisons with flaps extended, but tests with flaps retracted showed excellent estimation
up to a stalled flight condition.
17. Key Words 18. Distribution Statement
Angle of attack, Flight test, Derived AoA, Sensed AoA, Direct- This document is available to the U.S. public through the
measurement AoA, Stall margin, Stall protection, Simulation National Technical Information Service (NTIS), Springfield,

Virginia 22161. This document is also available from the Federal
Aviation Administration William J. Hughes Technical Center at
actlibrary.tc.faa.gov.

19. Security Classif. (of this report) 20. Security Classif. (of this page) 21. No. of Pages 22. Price
Unclassified Unclassified 107

Form DOT F 1700.7 (8-72) Reproduction of completed page authorized
ACKNOWLEDGEMENTS
Adaptive Aerospace Group, Inc. would like to thank Aspen Avionics, Inc., Aeroprobe
Corporation, and Garmin Ltd. for their assistance in this research, and members of the FAA Small
Airplane Directorate for their support.

iii
TABLE OF CONTENTS
Page
EXECUTIVE SUMMARY xi
1. INTRODUCTION 1
1.1 Purpose 1
1.2 Outline 1

1.3 Direct-measure sensors 1

1.4 Derived AOA algorithms 2

2. DIRECT-MEASUREMENT SYSTEMS 3
2.1 Garmin Multi-hole Probe (test article) 3
2.2 Aeroprobe multi-hole Air Data Probe (truth data source) 7

3. DERIVED AOA ALGORITHMS 8
3.1 Aspen EFD-1000 Derived AOA Estimation 8
3.2 AAG In-House Derived AOA Algorithm 11

3.2.1 Assumptions 12
3.2.2 Derivation 12

3.2.3 Advantages 12

3.2.4 Limitations 12

3.2.5 Implementation 13

3.2.6 Calibration 14

3.3 AOA derived from inertial measurements 15
4. SIMULATION TESTING 15
4.1 Simulation model 15
4.2 Sensitivity/robustness 17

4.3 Simulation results 20

4.4 Sensitivity summary 25

5. FLIGHT TESTING 25
5.1 Test aircraft 25
5.1.1 Instrumentation 25
5.2 Calibration procedure 26
5.3 Flight test procedure 28

5.4 Flight test results 31

iv
5.4.1 AoA Estimation Comparisons (Clean Configuration) 31
5.4.2 AoA Estimation Comparisons (20° Flaps and Gear-Down

Configuration) 37
5.4.3 AoA Estimation Comparisons (40° Flaps and Gear-Down

Configuration) 40
5.4.4 AoA Estimation Comparisons (Uncoordinated Flight, Clean

Configuration) 44
5.4.5 AoA Estimation Comparisons (10° Flaps and Gear-Down

Configuration) 48
6. DISCUSSION OF RESULTS 54
6.1 Direct sensed AOA measurement systems 54
6.1.1 Aeroprobe Test Probe 54
6.1.2 Garmin Retrofit Probe 54

6.2 Derived AoA systems 55
6.2.1 Aspen Derived AoA 55
6.2.2 ADAGE 55

6.3 Observations of differences between direct-measurement and derived AOA
methods 57
6.4 Lessons learned 57
6.4.1 Sensitivity to Vehicle Configuration 57
6.4.2 Elevator Power Limitation During Flight Test 58

6.5 Certification considerations 58
7. SUMMARY 60
8. RECOMMENDATIONS FOR FURTHER RESEARCH 61
9. REFERENCES 62
APPENDICES
A—ADAPTIVE AEROSPACE GROUP, INC. DIGITAL ANGLE OF ATTACK
G-BASED ESTIMATOR ALGORITHM
B—ADAPTIVE AEROSPACE GROUP, INC. DIGITAL ANGLE OF ATTACK

G-BASED ESTIMATOR IMPLEMENTATION IN SIMULINK/MATLAB
C—ADAPTIVE AEROSPACE GROUP, INC. DIGITAL ANGLE OF ATTACK

G-BASED ESTIMATOR CALIBRATION METHOD
D—FLIGHT TEST PLAN AND FLIGHT CARDS

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LIST OF FIGURES
Figure Page
1 Garmin GI 260 indicator on left side of glareshield in test aircraft 2
2 Initial location of Garmin multi-hole GAP 26 probe sensor in test aircraft 3

3 Relocated Garmin GAP 26 probe on test aircraft 4

4 Characterization of Garmin AoA indicator vs. calibrated AoA for two flap positions

(original sensor location) 5
5 Characterization of Garmin AoA indicator vs. indicated airspeed for two flap positions

(original sensor location) 5
6 Characterization of Garmin AoA indicator vs. calibrated AoA for four flap positions

(relocated sensor location) 6
7 Characterization of Garmin AoA indicator vs. indicated airspeed for four flap

positions (relocated sensor location) 7
8 Location of Aeroprobe sensor 8

9 Aspen PFD AoA display formats 9

10 Characterization of Aspen AoA indicators vs. calibrated AoA for six different

combinations of flap and gear positions (dashed lines refer to location of the upper
indicator) 10
11 Characterization of Aspen AoA indicators vs. indicated airspeed for six different

combinations of flap and gear positions (dashed lines refer to location of the upper
indicator) 11
12 Block diagram of the ADAGE algorithm 13

13 C vs. AoA line fits used for all data flights 14
N
14 Normal (Z-axis) accelerometer calibration curves used for all data flights 15

15 Cessna 172 Simulink® simulation model structure overview 16

16 Plot of trimmed, actual, and calibrated C vs. AoA for simulated Cessna 172 with no
N
flaps 17
17 Plot of trimmed, actual, and calibrated C vs. AoA for simulated Cessna 172 with 20°
N
flaps 18
18 Nominal 3-dimensional trajectory of simulated C-172 during maneuvering, approach

and landing flare (shown in north, east and altitude axes). Numbered maneuvers
refer to previous text. 19
19 Example parameter time history of effect of inserting bias in Z-accelerometer (red)

overplotted with a nominal maneuver trajectory (blue) 21
20 Schematic of on-board sensors and data recording system data paths 26

21 Example wind triangle pair from start and end of data flight 27

vi
22 Example of airspeed calibration curves vs. values from the Pilot’s Operating
Handbook (POH) from a data flight [5] 28
23 Per-flight and combined calibrations of the Aeroprobe Air Data Probe AoA

measurement 30
24 Comparison of sensed and derived AoA values during trimmed flight (clean

configuration) 33
25 Comparison of calibrated and two derived values of AoA during partial power stalls

(clean configuration) 34
26 Comparison of calibrated and two derived values of AoA during power-off stalls

(clean configuration) 35
27 Comparison of calibrated and two derived values of AoA during accelerated stalls

(clean configuration) 36
28 Comparison of various AoA measures and estimates during trimmed flight

(20° flaps, gear down) 38
29 Comparison of calibrated and derived AoA during partial power stalls (20° flaps,

gear down) 38
30 Comparison of calibrated and derived AoA during power-off stalls (20° flaps,

gear down) 39
31 Comparison of sensed and derived AoA during trimmed flight (40° flaps,

gear down) 41
32 Comparison of calibrated and derived AoA during partial power stalls (40° flaps,

gear down) 42
33 Comparison of calibrated and derived AoA during power-off stalls (40° flaps,

gear down) 43
34 Comparison of calibrated and derived AoA during uncoordinated flight (clean

configuration) 45
35 Comparison of calibrated and two derived values of AoA during partial power stalls

(clean, uncoordinated) 46
36 Comparison of calibrated and two derived values of AoA during power-off stalls

(clean, uncoordinated) 47
37 Comparison of various AoA measures and estimates during takeoff (10°) flaps +

gear down configuration 49
38 Comparison of calibrated and derived AoA during partial power stalls (10° flaps,

gear down) 49
39 Comparison of calibrated and derived AoA during power-off stalls (20° flaps,

gear down) 50
40 Comparison of various sensed and derived AoA values during takeoff (10°) flaps +

gear up configuration 52

vii
41 Comparison of calibrated and derived AoA during partial power stalls (10° flaps,
gear up) 52
42 Comparison of calibrated and derived AoA during power-off stalls (10° flaps,

gear up) 53
43 Comparison of calibrated and two derived values of AoA during accelerated stalls

(clean configuration, left 45° bank, at 3,000 ft; same data as plotted in Figure 27(a)
but with an expanded AoA scale) 56

viii
LIST OF TABLES
Table Page
1 Effect of operating in out-of-calibrated conditions on average and maximum AoA
estimate from the ADAGE algorithm 22
2 Effect of variation of uncorrected sensor location offsets on average and maximum

AoA estimate from the ADAGE algorithm 22
3 Effect of variation of uncorrected 10 degree sensor alignment error on average and

maximum AoA estimate from the ADAGE algorithm 23
4 Effect of variation of five degree thrust-line pitch angle increase on average and

maximum AoA estimate from the ADAGE algorithm 23
5 Effect of biases applied to various ADAGE input sensors on average and maximum

AoA estimate from the ADAGE algorithm 24
6 Effect of delays applied to various ADAGE input sensors on average and maximum

AoA estimate from the ADAGE algorithm, deg/s 25

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