@OK465
Reason: one cannot possibly write as one attempts to think
Boy, do I agree with that one!
Maybe under those ambient conditions full SS NU/full NU elevator at 330K comes up 'short' of +2.5G, just as it would come up 'long' of the -1G with full ND elevator.
I don't have the Va numbers handy.
Va at FL350 and 205t would be about 260 kts CAS. By definition the aircraft would stall at 2.5g at that speed. On my sums the elevator needed in those conditions would be about 9 deg without any help from the THS, so it would be a long way from coming up ‘short’ at 330 kts CAS
@HN39 & gums
Doesn't the achieved 'gee' come in? The sidestick may have been demanding +2.5 g, but the stalled airplane, even with elevator and THS fully NU, couldn't comply?
That’s where I started, but so far as I can see it doesn’t explain OK’s observations.
With full forward SS at 330 knots you get about 1/4 ND elevator deflection.
[Note: from subsequent discussion I take this to read “with full forward SS and with the system gains set at their 330 kts values”]
SD Flight Control page with sustained full ND SS input at both 330K & 200K in ALT2(B). It is constant, and the same in Normal at 330K. I don't even see full elevator deflection in Normal at 200K with a full ND SS input.
The logic that if present elevator is insufficient to provide the gee demanded by stick position then the system will increase the elevator deflection until the demand is satisfied must apply in both directions.
So if the demanded gee from full forward SS in OK’s simulation exercise was satisfied by ¼ ND elevator then the answer to his original question:
With gains fixed for 330 knots, can you get FULL nose down elevator in a developed stall?
is that you can get all you need to satisfy the limiting manoeuvre capability built into the control system, even if this is a lot less than full elevator travel.
However, if ¼ ND deflection was not enough to satisfy the commanded gee then following the logic that led to 30 deg NU but going in the opposite direction one should have seen more than ¼ ND elevator.
To repeat though – ¼ ND elevator seems to be nowhere near enough to provide the -1g manoeuvre limit built into the protection system.
And finally, I have just been looking at a video of an A330 simulation of AF447 stall and recovery kindly supplied by another PPRuNer, and one of the sequences shows full ND SS to be accompanied by at least ¾ ND elevator.
Help!