AF 447 Thread No. 10

[Lonewolf_50]

Dozy, I recall a few threads ago some detailed discussion on what the PF may have heard, and what may have fed him a false input into his SA via the audio channel. (If that sound registered, why not the cricket chirp of the Stall Warning, one wonders? )

With that considered, the A330 was bopping along at something near to Mach 0.8, which doubtless has a sound signature to it if you are in the cockpit. As the initial climb was underway, might there have been a subtle decrease in that ambient noise? As I have no time in the front seat of an A330 at cruise, I have no idea how noticeable that auditory cue would be for a given pilot, nor how subtle or obvious a change in noise related to the change in speed as the aircraft slows down before the stall.

Would the air flow, once stalled, of the plane falling at somewhere around 10-14,000 feet per minute have the same audible signature? I don't know. I can't recall if anyone had a good answer for that.

But it's somewhat irrelevant, other than as a distraction to the primary task of instrument flying at altitude. To establish SA, the noise is a secondary cue related to the information on the primary flight instruments. (FPV addressed by gums up a few posts). So even though this issue of auditory data input has been raised, we are back to disorientation in the visual domain, in terms of a good (or bad) instrument scan and seeing, as well as grasping, (or not) the information displayed on the primary flight instruments.

I am aware of how attuned most pilots are in the auditory channel. Our ears often tell us of a state change, or alerts us to start looking for indication of a change due to "that doesn't sound right." So I won't poo poo the idea that the audio domain may have contributed to disorientation in this case.

In my experience, a change in the sound of something (often engines, or for the rotary winged bretheren the sound of the rotors changing as well as engines) gets your attention and gets you busy until you either fix what's wrong, or at least satisfy yourself that you know "what doesn't sound right."

The CVR doesn't give us much in terms of any discussion they had along those lines, but that doesn't mean neither pilot was dealing with that. It will remain an unknown.