Recovering an approach stall

[Nicholas49]

Hello

I've had a search for stall recovery and found some interesting but fairly technical answers (e.g. a thread about a new Airbus stall recovery). I will try to keep this question as specific and focused as possible, otherwise I think this might get too technical for a non-pilot fairly quickly!

First, I appreciate this is (thankfully) a very unlikely scenario and that the stick shaker / Alpha Floor protection on Boeing / Airbus aircraft should prevent it from occurring. But as the THY accident at Schipol showed, it can happen. I would like to leave out of this question discussion of the circumstances leading up to a stall (which I know was controversial in that accident).

My question is: if you stall a large aircraft (A320/B737 and up) on final approach, does there come a point where you simply do not have enough altitude left to recover? Is there an altitude where you have to abandon trying to recover the stall and work on achieving the most controlled landing possible? Or is there always 'time' to do something?

Secondly, what is the recovery procedure for an approach stall? Do you first firewall the throttles? At low altitudes, I imagine you can not afford to pitch down too much? Will adding thrust bring the aircraft out of the stall easily given the power of jet engines?

Thanks
Nick

[BOAC]

does there come a point where you simply do not have enough altitude left to recover? - let's be clear here N49 - we are talking about a 'full' stall, not stick shaker, in which case yes? All pilots should be able to recover without hitting the ground from a stick shake event at whatever altitude since the aircraft is not about to fall out of the sky and simply needs a carefully handled power application to 'recover'Is there an altitude where you have to abandon trying to recover the stall and work on achieving the most controlled landing possible? Or is there always 'time' to do something? - unless it 'happens' right over the runway at a low altitude I suspect there would be very little one could do to do that.
Secondly, what is the recovery procedure for an approach stall? Do you first firewall the throttles? At low altitudes, I imagine you can not afford to pitch down too much? Will adding thrust bring the aircraft out of the stall easily given the power of jet engines? - power yes - loads of it because your energy needs urgent replacement. At very low altitudes, lowering the nose to unstall the wing is not an option. In under-wing a/c this gives, as you know, a significant and almost uncontrollable nose-up pitch, requiring immediate action once you are going away from the ground to 'recover' the pitch attitude, including power reduction, possible bank to lower the nose and trim. Yes, plenty of power to enable recovery, but you cannot then just sit there and wait for someone else to fly you out of what you have created. It requires very careful handling as recent accidents have shown.

I must emphasise for those of a nervous disposition that what you describe (a full stall) is very unlikely event in a normally monitored cockpit.

[Nubboy]

1. Yes, recovery will take both time and height. Running out of height before recovery is complete will always end in tears. Prevention is much better than cure.

2. You have to reduce the angle of attack that the wing is presenting to the airflow. Adding power on aircraft with underslung engines will always result in a nose up pitching moment. This will have a more marked effect in actual nose up pitch movement. The slower the aircraft is the stronger the pitch up effect. The response of the tailplane to produce a nose down pitching moment is dependant on many factors, airspeed (squared) being a major player in this scenario.
Reduce angle of attack first, then add power.

In slow flying excersises by flying a fairly long low to zero "g" manoeuvre you can demonstrate very low indicated airspeeds, well below the normal 1g stall speed, and still have full aerodynamic control. The answer is of course with a low g loading the wing is at a very low angle of attack and the airflow will stay attatched. Once the airflow has detatched, then the nose of the aerofoil HAS to be lowered, or rotated, into the oncoming airstream before it will reattatch and generate lift as expected. A big dose of power applied purely in the fore and aft axis (think DC9 or Fokker 100) will help as the aircraft will accelerate forward and therefore reduce the realtive angle of attack. High mounted propellor driven aircraft (think DHC8 etc) will further benefit from high energy propwash over the wing surface.
HOWEVER these are all secondary effects and you HVE to lower the nose to break the stall.