A320 Memory Items

Complete understanding of the Airbus A320 Memory Items. For training purposes only! Do not use it for flight.

STALL RECOVERY

Definition of Stall 

A stall is a condition in aerodynamics and aviation wherein the angle of attack increases beyond a certain point such that lift begins to decrease. The angle at which this occurs is called the critical angle of attack. This critical angle is dependent upon the airfoil section or profile of the wing, its planform, its aspect ratio, and other factors, but is typically in the range of 8 to 20 degrees relative to the incoming wind (“relative wind”) for most subsonic airfoils. The critical angle of attack is the angle of attack on the lift coefficient versus angle-of-attack curve at which the maximum lift coefficient occurs.

Flow separation begins to occur at small angles of attack while attached flow over the wing is still dominant. As angle of attack increases, the separated regions on the top of the wing increase in size and hinder the wing’s ability to create lift. At the critical angle of attack, separated flow is so dominant that additional increases in angle of attack produce less lift and more drag.

 

 

Stall Recognition

REMEMBER, a Stall is primarily an AOA problem. It is NOT directly a Speed Problem. Reducing AOA should be the priority. When thinking of the Stall recovery we must remember that our main aim is to avoid the Stall scenario at all times. In the event that you encounter a stall at any time you must apply the stall recovery procedure as soon as possible.

Remember that the first indications of a stall include but may not be limited to:

  • Aural stall warning

The aural stall warning is designed to sound when AOA exceeds a given threshold, which depends on the aircraft configuration. This warning provides sufficient margin to alert the flight crew in advance of the actual stall even with contaminated wings.

  • Stall buffet

Buffet is recognised by airframe vibrations that are caused by the non-stationary airflow separation from the wing surface when approaching AOA stall. When the Mach number increases, both the AOA stall and CL MAX will decrease. The aural stall warning is set close to AOA at which the buffet starts. For some Mach numbers the buffet may appear just before the aural stall warning.

A320 Stall Recovery Memory Items

As soon as any stall indication (could be aural warning, buffet…) is recognized, apply the immediate actions:

  • NOSE DOWN PITCH CONTROL……………………………….. APPLY

This will reduce angle of attack

Note: In case of lack of pitch down authority, reducing thrust may be necessary.

  • BANK………………………………………………………WINGS LEVEL

– When out of stall (no longer stall indications) :

  • THRUST……………………..INCREASE SMOOTHLY AS NEEDED

Note: In case of one engine inoperative, progressively compensate the thrust asymmetry with rudder.

  • SPEEDBRAKES……………………………………………………..CHECK 
  • RETRACTED FLIGHT PATH…………….. RECOVER SMOOTHLY

– If in clean configuration and below 20 000 ft:

  • FLAP 1…………………………………………………………………SELECT

Note: If a risk of ground contact exists, once clearly out of stall (no longer stall indications), establish smoothly a positive climb gradient.

Few more words about stall recovery 

The immediate key action is to reduce AOA

The reduction of AOA will enable the wing to regain lift. This must be achieved by applying a nose down pitch order on the sidestick. This pilot action ensures an immediate aircraft response and reduction of the AOA. In case of lack of pitch down authority, it may be necessary to reduce thrust. Simultaneously, the flight crew must ensure that the wings are level in order to reduce the lift necessary for the flight, and as a consequence, the required AOA. As a general rule, minimizing the loss of altitude is secondary to the reduction of the AOA as the first priority is to regain lift. As AOA reduces below the AOA stall, lift and drag will return to their normal values. When stall indications have stopped, and when the aircraft has recovered sufficient energy, the flight crew can smoothly recover the initial flight path. If in clean configuration and below FL 200, during flight path recovery, the flight crew must select FLAPS 1 in order to increase the margin to AOA stall. This may lead to a temporary flap overspeed in some cases, which is considered less important than ensuring the recovery is completed.

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