Seems like perhaps only 0.0001% of airline pilots have ever experienced any form of PIO and most do not understand the implications of the AF447 roll PIO encounter right after the autopilot dropped out.
All that wing rocking that Bonin did had the effect of destroying his trust in the reliability of his aircraft's control system so that later when the pitch control system did not behave as he expected (upon stall encounter), he assumed that that had failed too.
Folks have been minimizing the roll oscillation. Statements such as,"it wasn't that bad", "the roll rates were not that high", "he recovered roll control within 30 seconds" seem to predominate. I maintain that those with that view simply do not understand the nature of the PIO beast.
From my very limited exposure to a roll PIO in an older simulator, two PIO oscillation cycles is sufficient to grab your complete attention, and 30 seconds of fighting a PIO oscillation is a lifetime. The rest of you are going to have to take this on faith unless you also have had some sort of a PIO encounter. (And if you do have such experience, lets hear from you.)
Bonin's roll PIO was started by his initial excessively large roll input. The roll PIO was continued by an incorrect control strategy (Trying to get ahead of the roll oscillation). The reason he fell into this trap starts with lack of training in a simulator in roll direct at altitude (ALT2B mode). The other ~ 35 aircraft that successfully survived loss of airspeeds apparently did not encounter a roll PIO.
That Bonin used to fly gliders has very little bearing on the AF447 outcome. When the chips were down, he could not transition smoothly to manual control under night instrument conditions. If he had been gentle with the controls and had just kept on truckin, this would have been a non-event.
As Gums would say, "That's my story and I'm sticking to it."
