AF 447 Thread No. 12

[PJ2]

Hi Machinbird;

Re, "Do you still hold the view that PIO is a tangential issue?"

If I may enter a response to your question to PT6Driver, yes, I continue to hold that view because PIO doesn't explain the PF's simultaneous instant pitch-up, which continued to be held in until the stall.

Also, even if PIO occurred and even as quickly as the stick was moved, the stick movements and the airplane's excursions are not significant - at most 10deg of roll throughout until he got control of the roll, whereas the stick movement rearward and resultant pitch-up was within a second or two of the loss of airspeed information to the point of triggering the first stall warning, and continued upwards well past the time the roll was under control. In fact, the bank angle did not increase beyond about 10deg until almost 90 seconds after the initial loss of airspeed information and about 45 seconds after the stall warning had begun.

If as you say, pilots automatically correct for errors at the subconscious level and thus the PF corrected the roll, why was the pitch not similarly corrected, but actually increased, with an obvious, certain outcome for a transport aircraft at cruise altitudes?

I understand a slight delay while the airplane is stabilized and control maintained, but once control of the roll was achieved, SOPs for the abnormality would then be called for. However, by pitching up and thereby significantly destabilizing the aircraft, an abnormality became a loss of control and obviously rendered the calling for the original drill ineffective because they had another problem on their hands.

What, and where is the root-cause link between PIO and the loss of control less than a minute later?

PIO is not causal here, nor has the initial pitch-up been explained even though I had posited that the PF was "recalling" the UAS drill for right after takeoff, pitching the airplane to the memorized-15-deg attitude. It's simply a theory among others.

We're back to my original comment in July of 2009 on the second thread - if the PF had "done nothing", (meaning, just maintained pitch and power as the airplane doesn't care about loss of an airspeed indication), the stall would not have occurred and the roll would have been controlled.