Originally Posted by Machinbird
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.
Originally Posted by Dozy
You're right - however if I recall correctly from the mega-thread and the report's DFDR graphs, the PIO was on its way to being stabilised, and was almost there at the point the aircraft stalled (apex of the zoom climb) - suggesting that the PF was at least getting a feel for the roll aspect. Unfortunately the consistent backpressure (intentional or not) while doing so meant that stabilising the roll became something of a moot point as the aircraft went into a full stall.
Dozy, have you considered that the one size fits all roll direct control gain became more appropriate as the aircraft decelerated?
As for startlement effects, the initial strong control input that started the roll PIO could have been from startlement, or possibly from annoyance at having to take control. In any case, it was an unfortunate response to a situation that merely required minimal control inputs.