Validation of Stall Recovery Technique and Training_Claude Lelaie

VALIDATION OF STALL RECOVERY TECHNIQUE AND TRAINING

Presented byClaude LELAIE

© AIRBUS Operations GmBH. All rights reserved. Confidential and proprietary document.

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INTRODUCTION

•Following discussion between Manufacturers within the FAA Stall Training Group, it has been decided to create a generic template for stall recovery, valid for all types of aircraft. Adaptations can be made in line with aircraft specificities.

•All the procedure is based on a key item for recovery:

APPLY NOSE DOWN PITCH CONTROL TO REDUCE AOA


A380 STALL

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AIRCRAFT / SIMULATOR COMPARISON

• Before deciding to perform stall recovery training in a simulator, we had to check if simulators are reasonably representative when approaching stall.

• Two flights followed by a simulator session were conducted in April 2010 on A340-600 then on A320.

• Stalls were performed in degraded law (aircraft no longer protected) at low altitude in Clean and Landing configuration and at high altitude. About 30 stalls on A340-600 and 20 on A320.

• Some other tests were done to get more detailed information on the “old” procedure.


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RECOVERY FULL THRUST WITHOUT LOSS OF ALTITUDE (1)

- Tests performed on A340-600 in Direct Law, engines idle, Landing configuration, decelerating in level flight.

- At Stall Warning, IMMEDIATLY, Max thrust, maintaining precisely level flight.

- AoA values:- Stall Warning: 12.9°- G-break: 19°- AOA reached in the manoeuvre in flight: between 15.5 and 17°

- Same tests repeated in the simulator: - Max AOA value almost identical.- If waiting 2 seconds to push thrust lever, max AOA increased by

around 2°, which means that stall might be reached.


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- Tests in Clean only done in simulator.- Stall Warning: 9.8°- G-break: 13°- AOA reached in this manoeuvre: between 14°and 16°.

- The reason for this behaviour in Clean (flaps up) is that the engines have a low idle of and it takes more time than in approach configuration to reach max thrust.

- The simulator effect may increase slightly the final AOA compared to flight. However the AOA reached are well above stall, even with an immediate reaction.

- Position of engines would not change this conclusion for both configurations. During engine spool up there is a significant speed decay and AOA increase. Pitch up may not always be the key issue for this recovery technique.


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ALL THESE TESTS SHOW THAT THE PROCEDURE:

“APPLY FULL THRUST, WHILE MAINTAINING ALTITUDE”

CAN CONTRIBUTE TO REACH STALL CONDITIONS.


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BUFFETING CONDITIONS FOR A340-600

- There is a difference between the buffet conditions in the aircraft and in the simulator.

- Approach configuration :- Aircraft: almost no buffet, only configuration buffet, except close to stall.- Simulator: more buffet than on the aircraft from 15°AOA.

- Clean low altitude :- Aircraft: buffeting increasing with AOA.- Simulator: weaker than on the airplane and not increasing.

- Clean high altitude :- Aircraft: buffet starting at 6°, just before SW (7° ), increasing to become

really deterrent. Max AOA reached 13°.- Simulator: buffet starting later, 9.5°. Not as stro ng the aircraft

(fortunately!)


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BUFFETING CONDITIONS

• Simulators do not represent perfectly buffeting, mainly in clean, as buffet AoA is not tuned as a function of Mach.

• However, even if the AOA reached at buffet is not exactly the real one, it is not so important, as in the real life, stall buffet may appears in various conditions according to weight, altitude, type of manoeuvre... The key issue is that the trainee has to recognize buffet.


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STALL: SIDE ISSUES

• Aircraft :

• Clean: G break (stall) always difficult to see for a pilot.• Approach configuration: a well trained pilot may be aware

of the stall, not by pitch nose down cue, but more by lateral motions.

• Simulator :

• In all cases, no visible cue of stall.• In all tests in the simulator, we went to very high (and

unrealistic) AOA.

• A very important issue that have to be outlined in the training program is the risk of secondary stall , mainly at high altitude.


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CONCLUSION OF THE COMPARISON

• There is no significant difference between aircraft and simulator behaviour in the recovery procedure “stick forward”.

• Recovery up to Stall Warning or buffeting can be demonstrated with limited restrictions.


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STALL RECOVERY TRAINING

• After coordination with other Manufacturers in the FAA Stall recovery training Working Group, a basic training sequence has been developed and then validated.

• It includes stall recovery demonstration in the following conditions:

• Low altitude clean and landing configuration.

• High altitude.

• Specific exercise with startle factor


VALIDATION METHODOLOGY

•A training profile has been established on A320 after aircraft and simulator comparison.

•Four Airbus training pilots (TRIs) who had never been exposed to real stalls in flight before, followed this training. Then, they performed a flight on A320, to be put in the same situation than in the simulator: Stall Warning and buffeting.

•Their reaction allowed to validated (or not!) the training.

August 2010 Airbus stall training experimentation

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VALIDATION METHODOLOGY: PILOTS

• 1 Airbus Test pilot acting as Instructor• 4 Airbus Training Captains


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Age 42 41 60 44

Military background

French AF transport

French AF transport

No No

Nationality French French British Austrian

Total Flight time

4500h 7400h 13000h 14500h

Flight time on Airbus FBW

350h 1200h 8000h 5000h

Other a/c flown

C160 C160 707/747 757/767


EXPERIMENTATION PROGRAM

• Ground briefing• 30 minutes.

• A320 FFS• 3 hours dedicated session – same day .• Airbus Training Centre (CAE).

• A320 flight • 3 hours dedicated flight.• Airbus A320 prototype aircraft MSN1 fully equipped with Flight test

installation.


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LOW ALTITUDE RESULTS

• Some initial reluctance from one pilot (“most experienced”) to reduce positively AOA by moving stick forward before to increase thrust.

• When out of stall, discovery of pitch-up due to thrust increase which led to secondary stall warning (1/4).

•Reasonable fidelity of FFS versus airplane


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HIGH ALTITUDE RESULTS (1)

• Three “interesting” levels of buffet identified:• Notification by the pilot (0.05g peak to peak)• Maximum “accepted” by the pilot (0.1g peak to

peak)• Buffet onset as per regulations (0.2g peak to peak)

• Remarks:• Flight with no turbulence• No startle factor for pilots


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HIGH ALTITUDE RESULTS (2)

• Civilian pilots and even turboprop military pilots are not familiar with high Mach buffet (a first for all 4 pilots)

• Depending on aircraft type, buffet may be the first stall identifier at high altitude• A320 vs A330/340/380

• Need for:• Enhanced briefing • Exposure in the simulator

• But today some lack of FFS fidelity (at least for some a/c types)

Buffet simulation should be improved


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LOW ALTITUDE SYNTHESIS EXERCISE

• FFS only• Initial conditions: visual conditions, MLW, ADR3 OFF• High speed downwind (1500 ft AGL, 250 kt, clean)• Deceleration (Idle thrust, Full speed brakes out,

CONF 1/CONF 2/ Gear down)• Turn in final on PF side• PF concentrates looking on runway• Instructor switch off ADR on PF side (then degraded law) and

keeps idle thrust• Stall warning and recovery

•Very much appreciated as a synthesis close to the ground.


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CONCLUSION OF THE EXPERIMENTATION

•Stall recovery training possible in FFS.

•Low altitude synthesis exercise with some startle factor useful.

•FFS fidelity for buffet should be improved, especially at high altitude.

• Instructor training appears to be a key issue.


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Validation of Stall Recovery Technique and Training_Claude Lelaie