PPRuNe Forums - View Single Post - AF 447 Thread No. 7
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Old 31st Mar 2012, 00:32
  #1100 (permalink)  
NeoFit
 
Join Date: Sep 2009
Location: Around the World
Age: 70
Posts: 88
3,300 ft stall recovery

@ Mr Optimistic
Is there a consensus yet as to the altitude needed to effect a recovery by a typical crew ...

I am very glad to see how many answers you have had.

A Tech & physical view is my first answer but, instead of a fastidious (and probably wrong explanation) I have better to give you a short report:

...in good weather conditions, the aircraft suddenly started to climb adopting a steep pitch attitude and stalled. The crew managed to recover control of the aircraft and came round to land.
...
The throttle levers were then quickly brought back to the idle position. At the same time, the trimmable horizontal stabilizer started to move in a nose-up direction.

As the aircraft descended through 1,700 feet, at 10 h 43 m 22 s, with a speed of about 195 knots, the Captain asked for flap extension to 20°. The VFE, the speed limit authorized for this new configuration, is 195 knots. When the flap control was set to 20°, the thrust levers advanced and engine thrust increased.
The flight crew countered the nose-up effect resulting from the increase in thrust by using the pitch controls, with the auto-throttle (ATHR) remaining in automatic mode.
The throttle levers were then quickly brought back to the idle position. At the same time, the trimmable horizontal stabilizer started to move in a nose-up direction.
The nose up effect that resulted was countered by the flight crew through gradual nose-down action on the elevators. When the trimmable horizontal stabilizer reached its maximum nose-up value and the elevators also reached their maximum nose down value, the throttle levers, according to the FDR readout, moved rapidly to their stops.
In a few seconds, the flight path started to rise and the pitch attitude went to 60°. Witnesses saw the aircraft climb. It banked sharply to the left and the right and stalled before adopting a strongly negative pitch attitude ( .33 degrees) towards the ground.
The maximum altitude reached was 4,100 feet, while a minimum indicated speed of 35 knots was recorded. The stall and ground proximity warnings sounded during the descent.
The flight crew managed to regain control of the aircraft, with the lowest point being around a height of 800 feet, that is 240 meters from the ground.
In a few seconds, the flight path started to rise and the pitch attitude went to 60°. Witnesses saw the aircraft climb. It banked sharply to the left and the right and stalled before adopting a strongly negative pitch attitude ( .33 degrees) towards the ground. The maximum altitude reached was 4,100 feet, while a minimum indicated speed of 35 knots was recorded. The stall and ground proximity warnings sounded during the descent. The flight crew managed to regain control of the aircraft, with the lowest point being around a height of 800 feet, that is 240 meters from the ground.

4,100 minus 800 equal 3,300 ft stall recovery
(of course, air density is more important near the ground)
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