THREAD DRIFT - Low level stalling.
The AMS 737 accident investigation makes some interesting observations.
Note the pre publication comments to the Dutch Safety Board’s report - Appendix B. NTSB and Boeing comments starting on page 140 show just how a manufacturer will hang an operator out to dry in the event of an accident (even the absence of a comma). Boeing sates that the recovery was feasible with normal procedures.
Appendix M, page 201, gives the results of the Dutch simulator tests.
From a normal approach, a recovery from stick shake was possible within 450ft, but this depended on timely thrust application and the ‘correct flight technique’, which appeared to be maintain PLI.
“During the manual recovery, under the above given conditions
(pre accident scenario), it was necessary to push the control column fully forward in order to prevent the pitch value from becoming higher than the pitch limit indicator leading to aircraft stall. As the recovery progressed it was not always possible to maintain the aircraft pitch at or below the pitch limit indicator without trimming the stabiliser in most cases, but adequate elevator authority was available for at least 40 seconds before trimming was required. Control forces were maximum between 30-50 pounds and such that with one hand full forward control column deflection was possible. Evaluations of various recovery techniques showed that timely application of thrust could ensure recovery after stick shaker. In the event that thrust was not applied within a few seconds of stick shaker, the airplane could still be recovered by making control inputs to prevent the airplane from stalling.”
A full stall recovery:- “Boeing test flight data demonstrated that once the aircraft had stalled, the minimum loss of altitude required to restore the (un?) stalled condition was approximately 500 to 800 feet. When the aircraft stalled, the remaining altitude of approximately 400-450 feet was not sufficient to restore the situation. (page 203)
Appendix N, page 205, provides interesting comparisons of pilot awareness and reaction time in similar situations - much longer than assumed by Boeing; also the surprising number of previous events.
http://reports.aviation-safety.net/2...738_TC-JGE.pdf