17th Performance and Operations Conference
17th Performance and Operations Conference in Dubai
Update on stall procedure Presented by Xavier LESCEU – Test Pilot & Operational Expert Pilot
May 2011
17th Performance and Operations Conference
Contents 1
Stall phenomenon
2
AoA control
3
Stall recovery
4
New procedure
5
Conclusion
© AIRBUS S.A.S. All rights reserved. Confidential and proprietary document.
May 2011
17th Performance and Operations Conference
May 2011
Aerodynamic Review For a given configuration, a given speed and a given altitude,
Lift is only linked to AoA
For a given aircraft configuration and speed
An aircraft stalls for a given AoA © AIRBUS S.A.S. All rights reserved. Confidential and proprietary document.
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17th Performance and Operations Conference
May 2011
Stall
• A loss of speed can result in an aircraft reaching the stall AoA
• BUT it remains an AoA issue
Stall is only an AoA problem Low speed is a common contributing factor
© AIRBUS S.A.S. All rights reserved. Confidential and proprietary document.
Page 4
17th Performance and Operations Conference
Contents 1
Stall phenomenon
2
AoA control
3
Stall recovery
4
New procedure
5
Conclusion
© AIRBUS S.A.S. All rights reserved. Confidential and proprietary document.
May 2011
17th Performance and Operations Conference
May 2011
AoA Control – Pitch control effect The pitch control is a direct AoA command The
elevators control DIRECTLY the AoA.
A nose
down command has an IMMEDIATE effect :
Nose down command ⇒ AoA decrease
CG
AoA
© AIRBUS S.A.S. All rights reserved. Confidential and proprietary document.
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17th Performance and Operations Conference
May 2011
AoA Control – Thrust effect • Aircraft with engines below the aircraft Center of Gravity ⇒Thrust has a significant pitch effect Thrust increase ⇒ AoA increase
CG
AoA Thrust increase
© AIRBUS S.A.S. All rights reserved. Confidential and proprietary document.
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17th Performance and Operations Conference
Contents 1
Stall phenomenon
2
AoA control
3
Stall recovery
4
New procedure
5
Conclusion
© AIRBUS S.A.S. All rights reserved. Confidential and proprietary document.
May 2011
17th Performance and Operations Conference
May 2011
Stall Recovery When Aircraft is stalled
• FIRST: AoA MUST BE REDUCED • Release back pressure on stick or column • Nose down pitch input may be needed Note : Increasing thrust has an adverse effect on AoA reduction for Aircraft with engines below aircraft CG
• SECOND: If speed needs to be recovered • When stall indications cease, increase thrust with care due to possible pitch up effect
AoA comes first, speed second © AIRBUS S.A.S. All rights reserved. Confidential and proprietary document.
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17th Performance and Operations Conference
A380 Stall in flight test
© AIRBUS S.A.S. All rights reserved. Confidential and proprietary document.
May 2011
17th Performance and Operations Conference
May 2011
Approach to Stall v/s Stall Stall
Approach to Stall
• Stall indications already present
9 Artificial stall warnings 9 Some natural stall warning indications may be present
• Progressive airflow separation • Trajectory controllable with decreasing margin for manoeuvring
• Stall indications 9Artificial stall warnings 9Natural stall warnings ¾Buffeting ¾Lack of pitch authority ¾Lack of Roll control ¾Inability to arrest descent
• Airflow separated from wing • Trajectory no longer controllable
The change from approach to stall v/s actual stall is not easy to determine, even for a specialist. © AIRBUS S.A.S. All rights reserved. Confidential and proprietary document.
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17th Performance and Operations Conference
May 2011
Approach to Stall v/s Stall recovery procedure • The classic recovery procedure associated with “Approach to stall” was characterized by a recovery focusing on: 9 Maximum thrust application 9 Minimum loss of altitude
• Whereas the recovery procedure from an “Actual stall” has always focused on: 9 AoA reduction as first action, followed by a speed recovery if needed
© AIRBUS S.A.S. All rights reserved. Confidential and proprietary document.
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17th Performance and Operations Conference
May 2011
Need for procedure change • Drawbacks associated with this dual recovery approach are: 9 TOGA application may lead to an increase of the AoA 9 Reluctance to apply nose down input 9 Challenge to identify the change from “Approach to stall” to “Actual stall”
• Numerous accidents where the “Approach to Stall” recovery procedure 9 was applied whereas the aircraft was actually stalled 9 or generated a stall through thrust effect
A single procedure focusing on AoA reduction, as a first action, required to cover both the “Approach to Stall” and the “Actual Stall” recovery:
It is called the “Stall Recovery” procedure © AIRBUS S.A.S. All rights reserved. Confidential and proprietary document.
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17th Performance and Operations Conference
Contents 1
Stall phenomenon
2
AoA control
3
Stall recovery
4
New procedure
5
Conclusion
© AIRBUS S.A.S. All rights reserved. Confidential and proprietary document.
May 2011
17th Performance and Operations Conference
May 2011
New Procedure
• The FAA Stall Recovery Working Group issued a generic “Stall Recovery” procedure • A generic procedure for ALL types of aircraft • One single procedure to cover ALL stall conditions • Prevent full thrust/TOGA from being first action • Focus on AoA reduction
© AIRBUS S.A.S. All rights reserved. Confidential and proprietary document.
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17th Performance and Operations Conference
May 2011
Generic Stall Recovery Procedure STALL WARNING OR AERODYNAMIC STALL RECOVERY PROCEDURE Immediately do the following at the first indication of stall (buffet, stick shaker, stick pusher, or aural or visual indication) during any flight phases except at lift off. 1.
Autopilot and autothrottle…………………………….…… Disconnect
Rationale: While maintaining the attitude of the aircraft, disconnect the autopilot and autothrottle. Ensure the pitch attitude does not change adversely when disconnecting the autopilot. This may be very important in mis-trim situations. Manual control is essential to recovery in all situations. Leaving one or the other connected may result in in-advertent changes or adjustments that may not be easily recognized or appropriate, especially during high workload situations.
© AIRBUS S.A.S. All rights reserved. Confidential and proprietary document.
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17th Performance and Operations Conference
May 2011
Generic Stall Recovery Procedure 2. a) Nose down pitch control… Apply until out of stall (no longer have stall indications) b) Nose down pitch trim…….………………………………………..As needed Rationale: a) The priority is reducing the angle of attack. There have been numerous situations where flight crews did not prioritize this and instead prioritized power and maintaining altitude. This will also address autopilot induced full back trim. b) If the control column does not provide the needed response, stabilizer trim may be necessary. However, excessive use of trim can aggravate the condition, or may result in loss of control or in high structural loads. 3. Bank………………………….…………………………………….….Wings Level Rationale:
This orientates the lift vector for recovery.
© AIRBUS S.A.S. All rights reserved. Confidential and proprietary document.
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17th Performance and Operations Conference
May 2011
Generic Stall Recovery Procedure 4. Thrust ……………………………………………………………….. As Needed Rationale: During a stall recovery, many times maximum power is not needed. When stalling, the thrust can be at idle or at high thrust, typically at high altitude. Therefore, the thrust is to be adjusted accordingly during the recovery. For engines installed below the wing, applying maximum thrust can create a strong nose up pitching moment, if speed is low. For aircraft with engines mounted above the wings, thrust application creates a helpful pitch down tendency. For propeller driven aircraft, thrust application energizes the air flow around the wing, assisting in stall recovery. 5. Speed Brakes…………………….………………………………………. Retract Rationale: This will improve lift and stall margin. 6.
Return to the desired flight path.
Rationale: Apply gentle action for recovery to avoid secondary stalls then return to desired flight path.
© AIRBUS S.A.S. All rights reserved. Confidential and proprietary document.
Page 18
17th Performance and Operations Conference
Contents 1
Stall phenomenon
2
AoA control
3
Stall recovery
4
New procedure
5
Conclusion
© AIRBUS S.A.S. All rights reserved. Confidential and proprietary document.
May 2011
17th Performance and Operations Conference
May 2011
Conclusion
• Working together with other aircraft manufacturers, we have: 9Agreed the principle with the FAA Stall Recovery Working Group 9Issued a harmonized procedure focusing on AoA reduction as a first action
• The procedure was published mid-May 2010 and the corresponding FCTM end of May 2010.
© AIRBUS S.A.S. All rights reserved. Confidential and proprietary document.
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17th Performance and Operations Conference
© AIRBUS S.A.S. All rights reserved. Confidential and proprietary document. This document and all information contained herein is the sole property of AIRBUS S.A.S. No intellectual property rights are granted by the delivery of this document or the disclosure of its content. This document shall not be reproduced or disclosed to a third party without the express written consent of AIRBUS S.A.S. This document and its content shall not be used for any purpose other than that for which it is supplied. The statements made herein do not constitute an offer. They are based on the mentioned assumptions and are expressed in good faith. Where the supporting grounds for these statements are not shown, AIRBUS S.A.S. will be pleased to explain the basis thereof. AIRBUS, its logo, A300, A310, A318, A319, A320, A321, A330, A340, A350, A380, A400M are registered trademarks.
© AIRBUS S.A.S. All rights reserved. Confidential and proprietary document.
May 2011
