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Old 10th Aug 2010, 17:00
  #1855 (permalink)  
PJ2
 
Join Date: Mar 2003
Location: BC
Age: 72
Posts: 2,452
bearfoil;
You're welcome - glad it's of use. Even though retired, the questions remain engaging.
The FPV (bird) due to some need for it, in a cockpit that had become if not unintelligible, at least highly demanding? If flight data was displayed, and serviceable, augmenting the available cues with duplicative data might have been extraneous?
I wouldn't place too much emphasis on the FPV selection or loss of the information, (which was likely due to loss of other systems). This is a relatively small piece of information which a crew, wrestling with rapidly unfolding occurences and a rapidly degrading situation, would not reach for.
The crew would have wanted to simplify the screens and distill the cues to regain control, no?
No, I can't see this as part of any crews' thinking. "Screen clutter" is not an issue nor would one resolve this by de-selecting the FPV, (which re-selects HDG/VS).
The FPV u/s record fits with a screen that was either too busy or unavailable and a crew who were attempting a recovery from upset?
AFAIK, with one exception, the DMUs do not become "too busy", (over-loaded) and thereby struggle to display information. That one exception is, (and I have seen it), when "Navaids" or "Waypoints" is selected for display and the scale of the ND is on 320nm. If there are a lot of these in the database, the display will sometimes flicker, but I think it is a non-issue in these circumstances.
The other possibility would be that the A/P trip happened after loss of control and the pilots may have been incapacitated due to the loads of uncontrolled flight and the computer volunteered an admission of degraded control/available instrumentation?
Abnormal Attitude laws disconnect the A/P at 25degNU, 13degND and 50deg Bank, (if I recall correctly - not near my FCOM at the moment). Such attitudes are a long way from causing an incapacitation of the crew "due to the loads of uncontrolled flight". IOW, while such attitudes are extreme, they are still within the realm of crew controllability, while upside-down or pitch-vertical (up or down), would become a far greater challenge.

In terms of upset, "wings level" would come first, even before pitch, primarily because of the potential for spiral dive if wings are not first leveled. The exception, some will argue, may be in very high pitch angles where a "roll-off" to get the nose down first, may be more successful than a maximum-effort push-over. In any case, the FPV is not the information to be sought regarding these priorities as the primary guidance is attitude (closely followed by speed), in the moment, not trajectory which is what the FPV displays - in short, one uses as much sky as is necessary and available to return to controlled flight.

I think another way to put it might be, these are not moments where fine-tuning the response is a priority and such selections (or even paying attention to) lateral 'g' loads as indicated by the FPV, is not going to happen - unless heavily trained for and often (and we as an industry don't do this), the reaction (once past "startle") is more instinctual than measured.

I believe the crew had both PFDs (horizons) but stand to be corrected given the time that has passed since I read the reports.

Regarding rudders and fins, parts of the Canadian TSB Report on the Air Canada upset is worth reading I think.

Cheers,

PJ2.

Last edited by PJ2; 10th Aug 2010 at 17:07. Reason: adding comments re FPV
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