Hi gums,
Originally Posted by
gums
The normal law and the alternate laws are not "attitude" biased as one would expect in the old days of the autopilot "attitude hold" mode. The thing is programmed to hold a gee! In Normal, the pitch attitude is taken into account, so it does not try to hold one perfect gee if in a climb or descent, but whatever gee is required for the pitch attitude. So in some sense, it has an attitude function built in. Once outta Normal, it appears to be strictly a gee command with pitch rates blended. AoA seems absent to any large degree.
Would you be so kind as to elaborate on the bolded sentences? Source and so on?
Why do I ask? Two things:
-
AFAIK, stick free the aircraft holds its path, not "1 g". It may be that the path gives 1g (often it is!) but the law is "g demand" (i.e. stick not free) not "g holding".
- I was unable to find any credible document indicating that the stick free longitudinal behavior is different in Alternate law versus Normal law.
Thanks in advance
Hi rudderrudderrat,
Originally Posted by
rudderrudderrat
Originally Posted by Clandestino
However, from DFDR data it can be seen that aerodynamics were not enough to keep AF447 stalled; at about 2:11:45, THS is winding up and is 2-3 degrees shy of full nose up, elevators are fully nose up, as trust levers get retarded N1 goes down and nose drops from +15° to -10°.
The aircraft had 45° angle of attack.
Even if the nose was lowered by 25° I still make that 20° angle of attack.
Do you still think that that "aerodynamics were not enough to keep AF447 stalled"?
The aerodynamics alone: you don't know. What you may notice is that the THS & elevators, commanding nose up, might have slightly influenced clean aerodynamics at that point.
What you don't know is what AoA will have been reached with thrust idle + stick full nose down and maintained there as long as needed (meaning eventually the elevators and THS would have winded down).
It can't be proven until test flights take place, and we all know there won't be such tests and why. OTOH, all indications so far show the nose would have gone down, down down, and the AoA would have followed.
Therefore I too do think that aerodynamics were not enough to keep AF447 stalled, and that this PoV ('locked in stall') is irrelevant. And it also may be used to used to divert attention BTW (this is not for you, rudderrudderrat, I'm thinking about organisations that have an agenda, out there).
Cheers.