Continuation
My educated guess is that the autopilot did not disconnect because of the up elevator trim or because it was kicked off by high AOA. I say this because the reports indicate that the autopilot disconnected before the shaker/pusher activated. If that is correct - It disconnected because its ability to control the bank angle had exceeded its limits. That’s my theory – and that’s all it is; a theory.
When the disconnect occurred, the nose up elevator trim caused the initial pitch up. That pitch up caused the wing to stall - very suddenly and immediately.
The reports tell us that an attempt was made to retract the flaps (and maybe the gear). If that is true – it was mostly likely because the PF associated flap extension with the upset. In any event in stall recoveries in this category of aircraft Training often says “max power, flaps up, gear up”. Again, I have no idea what that airline teaches, so that thought is pure speculation. In any case I consider it to be essentially irrelevant in this instance.
Again, I know nothing about this a/c type but my guess is that the elevator trim is electric - and there is no trim wheel in the airplane (something I personally find objectionable – just a quirk of mine). Therefore, it is especially difficult to tell where the elevator trim may be at a given point in time, especially at night in a dimly lit cockpit, when the a/c is being flown by the auto pilot, holding altitude, undergoing power changes and decelerating – all at the same time.
An upset in a transport category airplane is simply not recoverable at an altitude of 1500 ft AGL; certainly not on instruments and totally unexpected. Most if not all upsets are never anticipated.
The very best among us have worked experimental upset scenarios in simulators trying to develop satisfactory recovery techniques (down in MIA if I recall correctly). They developed some ideas but no real solutions and no brilliant recovery technique. Unless there is a great deal of altitude below you, the only thing they managed to prove was that upsets in T-category aircraft are not recoverable. They must therefore be avoided by all possible effort.
Avoidance isn’t cut and dry. Each aircraft is different and one size just doesn’t fit all. Likewise, Icing is a different ball game in each machine. As someone before me pointed out: “In aviation there are three types of ice: Good Ice, Bad Ice and Hazardous Ice.
Good Ice is found in the galley”.
This is NOT the first incident or accident to result from an upset. Perhaps it is the first in the Q-400 but that aircraft can't be so unusual that it 'can't happen'. We all know Murphy’s Law.
Several upsets have occurred in the Brasilia. At least two that I know of resulted in accidents, one of them as tragic as this one. More than one has resulted in structural damage. ALL occurred while the airplane was being flown by the auto pilot and several in VMC. There have been several in versions of the ATR, especially the -42, at least one of which was also a fatal accident in this country. Its obvious or should be, that these new generation turboprop aircraft require their own rules of operating technique and flight crew understanding. The results indicate that some of the invented simulator scenarios just aren’t cutting the mustard. We just can’t keep repeating the same thing over and over an hoping for different results.
It should also be noted that upsets have occurred in heavy jets as well and in small jets too – also involving autopilot operations and situational awareness.
Unless we choose to make ourselves aware of history and act differently as a result of our knowledge, history will surely repeat itself.
It is not my purpose to affix blame or to be critical of anyone. Its not about blame, its about cause and effect.
It is my purpose to do whatever I can to avoid unnecessary repetition of tragedy or even white-knuckle operation. I am willing to err on the side of safety in that effort. I also believe in the axiom – knowledge is power.
If you see error in this phase 2 hypothetical please point it out. I won’t be embarrassed if I’ve made a mistake. At this point I am willing to rule out the tailplane stall theory.
“Aviation in itself is not inherently dangerous. But to an even greater degree than the sea, it is terribly unforgiving of any carelessness, incapacity or neglect.” — Captain A. G. Lamplugh,
PS. Sorry for being so long winded.
