Well done Clandestino (and others with a sound understanding of flying and the perilous state of affairs that this industry has become). At last some comments that help destroy the myths and pointless rants that sometimes appear on these threads.
Ten years before this accident, Airbus Chief Test Pilot Capt W Wainwright wrote an article on Stall recovery - it is doubtful many Airbus pilots have read it. Had the AF447 crew been taught and applied these techniques history would be different:
http://www.google.co.uk/url?sa=t&rct...NBc9_0_SR-U9Sg
Adding power when stalled is poor stall recovery advice. For FAR 25/JAR25 machines with underslung engines, stall recovery for flight test: Unload by reducing AoA - no thrust is added until around 20% above Vs due to the negative effects of adding thrust. It also happens on light propellor aircraft where adding power alone also adds yaw which can induce incipient spin.
How does a glider recover from a stall?
An aircraft can be stalled at any airspeed depending on wing loading - so speed alone is not the only factor.
NASA carried out a stalling project from FL450 with a B757 some years ago. The machine was held at the stalling AoA (only a few degrees nose/pitch up) with full TOGA thrust. It continued to decend at over 5000fpm until standard stall recovery (reduce AoA) technique was used.
Whilst Deep Stall recovery requires a very large AoA reduction (not just lowering a few degrees of pitch), the reason the A330 was heading for the ocean floor almost tail first was because of high thrust vector and aft control column inputs.
I have to completely disagree with the concept of adding full thrust and/or banking to break a stall whatever the altitude. All that is doing is creating a worse Upset senario for both the pilots and (if a high speed dive ensues) the structural integrity of the aircraft. Using roll control when stall buffet is present can also lead to a spin.
The only time to add full TOGA thrust would be in a low level pre full stall senario in conjunction with an AoA reduction. Without auto trim, adding power alone in both an underslung engine and a tractor propellor aircraft will cause a nose up (relative to pilot) pitch which is traditionally negative longitudinal stability.
Whilst W&B have their part, in general (unlike straight wings), swept wings also trend to provide further negative longitudinal stability at the stall with a nose up (relative to pilot) pitching moment as the spanwise flow is modified and the boundary layer thins from the wing tips first. Without wing fences/ Vortex Generators, this also reduces any outer wing/aileron control effectiveness.
We have already seen in the past few years several major incidents and accidents where pilots just adding power to try to recover form a stall:
Thomson Fly B737 Bournemouth UK
:
http://www.skybrary.aero/bookshelf/books/875.pdf
Norwegian Merlin Student Stall:
Fatal Merlin crash puts spotlight back on stall recovery
Even a tractor prop aircraft at high IAS with a sudden reduction in power will (for stable design) result in a pitch down - this is positive longitudinal stability which helps to reduce AoA and therefore would unload the wings.
Clearly, what is permissable within the flight envelope of a Fighter jet (some of which are capable of 10G per sec wing loading changes) is not so with an airliner.
Banking an aeroplane to a high AoB is fine for aerobatic and military machines where a high Rate of Decent is required. For larger hardware it can be fatal - not only at low level in the following examples but due to in flight breakup in the subsequent recovery form a high speed dive.
B52:
C17:
The other issue is Va (manoeuvre speed) which is the maximum certified wing loading at the stall (stalling at max "g") and permits ONE control to maximum deflection, ONCE - not simultaeous or multiple roll and pitch control inputs:
American Airlines Flight 587 - Wikipedia, the free encyclopedia