Machinbird in
Post #403
Suppose a pilot in a stall such as AF447 was in, places the stick full aft for a period of time and the THS runs up to its limit. If he now releases the stick and allows it to center, will the elevator center or remain at its last (30 degree nose up) position?
Interesting proposition. My initial response is to consider what the aircraft would do longitudinally if in DIRECT LAW.
We know that the CG is forward of the Aerodynamic Center or Neutral Point. That being the case, the Elevators must provide the following:-
(a) The AFT CG position is defined as - 1° of elevator deflection is required to pull a 1g Load Factor, and
(b) The FWD CG position is defined as - the maximum elevator deflection must provide at least the maximum acceptable load factor of 2.5g.
A problem exists in the AF447 stalled situation, i.e. a lack of TAS and faulty CAS, e.g. NCD.
But the aircraft is in ALTERNATE LAW, and the pitch characteristics are the same as NORMAL LAW which seeks a G response to commanded Elevator angle from the SS and as modified by the FCPC. Exactly how the FCPC preconditioning will react with dud air data is the big unknown, but with the aircraft stalled and falling at a nominal 1g, what is known from the DFDR traces is that a reduction of NU Elevator resulted in a reduction in pitch attitude, as would be expected with a CG well FWD of the Neutral Point. Not forgetting the pitching moment resulting from variations in thrust.
So your question -
If he now releases the stick and allows it to center, will the elevator center or remain at its last (30 degree nose up) position?
- seems irrelevant, though I suspect what you were asking is, "
If the SS was left to center, what would the THS eventually do?"
Apologies if I have misinterpreted your post.
