Stalls and ailerons
Quotes
jcjeant:
"Think ... maximum deflection to the left (for 30 seconds .. what a very long time) and the aircraft would not embark on a sharp left turn (or bank angle) ... very strange ..
What can prevent him from taking a left bank angle ?
Remember that it is to counter a bank angle to the right ..
So the force pushing the plane to a bank angle to the right should be very strong !!!
Wat can be this force ? .. what can produce this phenomena ?"
HN39:
"A stall ...?"
PA_18_151:
"The question jcjeant should really be asking is why was the PF trying to use aileron to counter wing drop."
Absolutely, but jcjeant's question is a perfectly understandable one from a non-pilot. For the benefit of the others, let me explain that, when we do our basic flying training on conventional light aircraft at a flying club or wherever, our ability to recover from the approach to the stall and the stall itself has to be demonstrated before we can be sent off solo. It is drummed into us that the use of aileron to keep the wings level approaching or in the stall is an absolute no-no. Roll must be countered with rudder.
Many light aircraft are fairly forgiving in that respect, perhaps because the wing/body angle washes out towards the tip-mounted ailerons. Others will react by rolling against the pilot input as the downgoing aileron stalls, usually leading to a spin. This is the classic trap from the early years of aviation.
In jet transports, when practising the approach to the stall, use of aileron (and associated roll-spoiler) is normally permitted. At the point in question, AF447 was already in a super-stall, although we have to assume that the PF had not diagnosed it. Quite what effect this was having on lateral stability is unclear, bearing in mind that the PF had been working hard on lateral control long before the aircraft stalled. Now, the whole wing was super-stalled.
I am reliably informed that, in addition to the fact that the aileron inputs might have been counterproductive (we don't really know), the associated roll-spoilers would have had little or no effect. Well aft on the wing chord, I guess they would have been in relatively stagnant air.