Originally Posted by Clandestino in response to Chris Scott
You suggest that A330 is sensitive beast that has to be treated gently. I say that it is exaggeration and you can throw her around hamfistedly at cruise altitude, in alternate law for 4 minutes with normal acceleration varying between +1.96 and -0.26G with end result being no worse than just utter mess in cabin and galleys.
Originally Posted by Machinbird
Do that in roll direct and I suspect you will learn gentleness, and there might even be an additional mess in the cockpit.
Alternate1 and Alternate2 laws might work similarly in pitch, but they bear no resemblance in roll.
Originally Posted by Clandestino
What relevance it has to AF447? For Finnegan's sake it didn't crash in spiral dive or rapid roll to ocean but in upright stall! That's what happens when you try to pull the aeroplane where she just can't go perfomancewise.
This the relevance.
Bonin applied excessive control inputs that the aircraft would have tolerated had it been in Alt1 law, but since it was in Alt2b, a roll direct law, the sensitivity of the roll channel was far higher than he expected and he set up a roll oscillation that lasted 30 seconds. During this same 30 seconds, he inexplicably pulled up into a climb that used up virtually all the aircraft's energy reserve above stall speed. In my opinion, this roll oscillation fits the general definition of a PIO.
What most readers here do not seem to appreciate is that a PIO event will grab 100% of your attention while it is in progress. My only experience with PIO was in an early visual simulator and it was brief and without consequence. Nevertheless, it made a deep impression. The best analogy to it was like unexpectedly tripping and beginning to fall and looking around desperately for a handhold.
In effect, while piloting an aircraft, the aircraft is your body. Would you be able to execute a checklist or maintain a scan while your body is falling out of control? This type of 'emergency' will cause a tremendous flow of adrenalin in those without prior experience. Will you be able to pilot rationally immediately after such an event? This is my take on the cause of AF447's loss.