Friday, March 6, 2009

The safest form of transport

84 pages and counting on the pprune forum:-


Today we simulated the Turkish scenario in a B733 simulator. At 1800 feet AGL and established on the ILS, we retarded the throttles to idle, simulating what the Turkish B738 autopilot did. The aircraft started trimming slowly at first, and then more and more rapidly to maintain the glide slope. We allowed the stick shaker to activate and after around 8 seconds of stick shaker we applied full thrust and attempted a recovery without reconfiguring. With the control yoke pushed as far forward as it could go, the aircraft started to accelerate and a climb was initiated and it appeared that we were recovering. Note that this is with the yoke pushed forward against the forward stop. Then, all of a sudden, the aircraft entered a deep stall as the rudder lost effectiveness and the aircraft forward speed rapidly bled off and we entered a 6000 ft/min plus rate of descent until impacting the ground in an apparent tail low attitude.

The reason for our not recovering was due to the extreme amount of trim the autopilot had applied while attempting to maintain the glide slope. The only way that we could have recovered would have been to apply extensive nose down trim during the initial recovery.

We performed this exercise twice and both times produced the same result. We firmly believe that this is what was the cause of the Turkish crash.

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