Originally Posted by PJ2
The eight degrees is nothing to be concerned over, nor are the back-and-forths; such minor gyrations don't lead to a complete loss of control, and he got it under control. Now, over thirty-five degrees bank at that point would be something to comment upon.
I've never understood the fascination with this initial roll and subsequent minor PIO. There's just nothing in it - it's what the airplane would do with just a bit of lateral stick and he very quickly got it right. But it doesn't stall the airplane.
Long experience with the perversity of aviation accident causes makes me extremely suspicious when I see anomalous behavior.
While I absolutely agree that the 8 degree initial bank was no big deal, I am not so comfortable in describing the PF's initial wing wobbling as minor gyrations. PF was using a substantial portion of the aircraft's lateral control authority to drive this oscillation, and any pilot with high altitude handling experience knows that this is a bad idea for a number of reasons. Although the bank angles achieved were not very spectacular until after the stall, the roll rates were very high. I do not believe an experienced pilot would have exceeded 1/10th of these lateral control inputs in "normal" Alt 2 flight. (But I have to provide the caveat that I have never flown the 'Bus)
From this chart I provided earlier, the first 4 roll half oscillations were on the order of 15 degrees each. Each one was accomplished in just over 2 seconds and PF then accelerated his inputs to drop his average time between reversals below 2 seconds. This is too much movement for the average pilot to calmly ignore.
I suspect his initial difficulty in controlling the wing roll attitude grabbed his full attention. There are hints of this in the type of strategy he used to control the oscillation. Instead of backing out of the loop for a moment and letting things calm, he accelerated his inputs to "get ahead" of the oscillation. You can see this by just graphing out the reversal intervals. As I have said a few times before, he actually got so far ahead with his large inputs that he caused at least two phase reversals of the oscillation. Yes, he did finally get the aircraft under a semblance of control- but he did it with high gain inputs. This is very indicative of an agitated mental state (IMHO) at the point just before the stall. You don't fly smooth when the adrenalin is pumping.
I am not an engineer but my pilot instincts tell me that below FL200, opportunity for a successful recovery rapidly reduces, mitigated only by the thicker air. It would take very aggressive action on the controls to do so and we're just not trained to do that. That means the guy at the controls at that very late point in the event would be of a mindset that recognizes only one way out with seconds to decide..., "15deg nose down, 15,000ft away from earth doing 18,000fpm down is my only chance" and that capacity to think and do that is, I expect, rare.
This second sentence is very concerning to me. From observing the posts of others, I know that stuffing the nose down is avoided like the plague in airline flying-and for good reason when you have people in the back of your aircraft.
For a tactical experienced pilot, there is a concept called unloading the wing. If you establish a ballistic trajectory with your aircraft, you do not require lift and this allows your aircraft to accelerate much more quickly than it would while maintaining high AOA. In a ballistic trajectory, your aircraft will not stall. This is the core idea behind many tactical maneuvers. In airline use, you would not have to fully adopt a zero g ballistic flight to recover from a potential low speed excursion. 1/10th g is sufficient to keep most things stuck to the floor and still provide almost all the benefit of zero g. Unloading is a concept that every jet pilot should have in their back pocket through practical (airborne) flying experience. (You cannot do it in a Sim). A pilot who understands the concept won't have difficulty getting the nose down to get flying. The only limitations are likely those built into your flight control system.