PPRuNe Forums - View Single Post - AF447 final crew conversation - Thread No. 1
Old 12th Feb 2012, 20:35
  #1312 (permalink)  
infrequentflyer789
 
Join Date: Jan 2008
Location: uk
Posts: 806
Originally Posted by Brian Abraham View Post
It's hard to imagine the pilot of a non Airbus holding full back stick and manually trimming full nose up no matter what the circumstance.
Really ? Pop-quiz - which (now somewhat fragmented) aircraft is this then:
The crew did not take any action to re-trim the aircraft to the desired speed, so, once the nose down pressure was released on the control column, the aircraft pitch started to increase again
[...]
The aircraft re-entered a stall situation (AOA reached its maximum values of around 26 at 00:41:09). Contrary to any stall recovery procedure, the control column was initially kept backward and gradually increased over the next 17.
[hint - it's one of those hard-to-imagine non-Airbuses]

The power of a trimable stab is such that it becomes the primary pitch control, with the elevator assuming the role of a short term pitch modification.

The pilot of old automatically knew the trim state of the aircraft because he put it there, where as the Airbus, I gather, the pilot is only aware of where the automatics have put the stab is by reference to instrumentation.
Auto-trim is damned whatever it does.

447, auto-trim stays on, pilot pulls back through stall warning, trims up in stall -> "auto trim should hand back to pilot in stall"

Perpignan, auto-trim does hand back to pilot, pilots never re-trim, leads to fatal secondary stall. Would have been much better chance of recovery had auto trim followed pilot commands. -> "auto trim should follow pilot commands in stall"


It's not just an airbus problem however:

Ethiopian, Beirut - mis-trimmed, pilots never re-trim, pulled back through fatal secondary stall.
Turkish, Schipol - auto-trim does hand back to pilot, pilots never re-trim (recovery fails because they let throttles go back to idle again however)
Colgan, Buffalo - auto-trim might have had a hend in setup, but they pulled back all the way down and pulled the flaps in just to be sure...


Sure, there may be a pattern there somwhere, but "airbus" ain't it.
infrequentflyer789 is offline