Low-level stall cause? The clues are scattered throughout the posts. Time somebody gave it a name.
1. fully configured at 3nm in approx. 1000ft with F30 and being distracted by heavy training on the flight deck on final approach, speed starts dropping and nobody realises.
2. the issue with the autothrottle seems plausible -
fully configured at 3nm in approx. 1000ft with F30 and being distracted by heavy training on the flight deck on final approach, speed starts dropping and nobody realises that the A/T is off. aircraft gets upset.....
3. The appch looked fairly normal until 600ft (09.25.08Z), in regards to glide path and speed.
4. I`d speculate that something odd happened just afterwards, as the speed starts to decay. I see the following happening: Down to 600ft all working well and aircraft being flown with A/P and A/T engaged. Shortly afterwards, around 500ft the automatics are disengaged and for some unknown reason(s) proper speed management was not maintained, or maybe they assumed the A/T was still engaged when it was not. The mistake was only noticed very late down the approach and they were caught without options on a low energy/low altitude scenario. Perhaps they even tried to initiate a GA (some survivors stated a sudden increase in engine power shortly before impact, if I recall correctly ) and hit the tail in the process.
5. Witnesses on the ground describe nose high attitude, followed by a dive to the ground.
6. The aircraft hit the ground tail first in a high rate of descent with low forward speed. This is obvious from the photos of the crash scene.
When the FDR and CVR information is released, I expect that it will confirm a low altitude stall, or approach to stall, with an incorrect or incomplete stall recovery.
See this
linked image
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In the 15 seconds between 09:25:23 and 09:25:38 UTC, at around 350 to 400ft agl, soon after breaking cloud, and with Auto-throttle not obliging with any drag-opposing thrust, the aircraft stick-shaker would have cooked off and the surprised pilot would have disconnected the autopilot and selected an SOP max-power, yet immediately encountered the fierce zooming effect of low-speed max power pitchup. However combined with that nose-up couple, at autopilot disconnect, additionally and fatally, courtesy of the insidious effect of auto-trim, he'd have also unexpectedly liberated a yoke-full of max elevator backtrim and nose-up stabilizer. That he would have been then pushing and fighting that powerful nose-up pitch couple would be without question. But, before we consider what happened next, what would the F/O have been thinking when he saw the nose pitch up? Would he (could he?) have understood what was happening? Think of that Egyptian Captain returning to the cockpit of Egyptair 990 and seeing the suicidal Batouti seemingly fighting for control. In the very short time available, would the Turkish captain have been able to communicate the nature of his problem? Food for thought, what action might the F/O take? helpful or not? ..... but back to the instant pitch-up....
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Ever tried a very nose-high power-on stall? Few pilots do this as an exercise, and if they did, then they'd better do it at height. Why? Because at the point of stall the nose pitches down to an alarming "face full of dirt" attitude (which you'd only appreciate as you rebroke cloud again). What happens next? Well you have a very limited height in which to recover from the ensuing dive - but because of the ground-rush phenomena, believe me when I say that
you will be trying very hard. Low-level aerobatics pilots will know how disciplined you have to be to recover from a misjudged low-level pitching plane nose-low maneuver, in order to avoid going beyond buzz, buffet, judder into the g-stall .... and then performance destroyed, into the dirt. Performance with gear and flap down will be marginal, even with max power.
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When you g-stall due to a panic-stricken pitch-rate, you kill the lift vector at a speed well in excess of the one g stall speed, no matter where the LE and TE flaps are. I need no further convincing that TK1951 had made it most of the way around the bottom when the ground intervened.... and the tail departed and the cockpit was then counter-pitched down, very hard, into terra firma.
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What needs to be determined is when and how (or why?) the auto-throttle became disconnected or disabled. Radar altimeter spikes? CB pulls? A large municipality's RF interference with that RADALT? A new high-zap directionally aimed terror weapon designed to interdict vulnerable auto-land systems? Or was it simply a directive or decision to demonstrate to the trainee a manually throttled approach (which was then overlooked by ingrained habit patterns?).
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Has anybody ever practised this nasty in a simulator as part of a recognized syllabus? I doubt it. We do these things to ourselves - but with the able assistance of automation.