Lyman:
Between this thread and a number of AF 447 threads in Tech Log, there have been posts by credible contributors that indicate that a good estimate <---- of the time it takes to unstall that aircraft (depending on when recovery was begun and how stalled it was) lies somewhere between 10,000 to 15,000 feet. Maybe.
Part of that estimation seems to be based upon "if you hold it in for X long" it takes you longer to recover than if you begin recovery right after stall onset.
What the collective judgment seems to be is that the longer one holds it in (as the crew did) the higher the AoA will become (up to a limiting value?) hence the longer to recover (time it takes to change AoA to "flying" rather than "stalled")
IF AND ONLY IF
the crew discerns that "we are stalled, time to commence recovery"
AND
the crew begin to lower the nose, lower the AoA, and adjust power (???) as appropriate.
BEA seems to me to be in a "damned of you do and damned if you don't" position if they open that can of worms.
The DATA they are working from never shows stall recognition.
Therefore, BEA can't guess how high the AoA MIGHT have been when initiation of recovery was commenced, and they thus cannot speculate on how possible it was to recover.
To toss out a few examples:
Were stall recognition made at 36,000 feet (fairly early into the stall), you'd have one estimate of how long to recover if X nose down was done.
If "we are stalled" recognition is made at 30,000, another estimate
If "we are stalled" recognition is made at 25,000, another.
And so on.
There is also, due to lack of a standard trained response for stall recovery (fleet wide?), unanswerable recovery methods such as
-how much nose down
-what power
-configuration
which can only be derived in hindsight regarding the following:
"Well, how much nose down can you expect the crew to use to unstall?"
All BEA might be able to speculate about is where the point of no return might have been. They have insufficient data (IMO, to include training and wetware issues) to work with to allow them to approach an analytical statement like the following strawman:
"Had they acknowledged stall at 13,500 feet (or some such number) or less, it would not have mattered, since it takes more than that to unstall from X AoA. Had they arrived at the conclusion that "we are stalled" at 14,000 feet, we believe for reasons x, y, and z that the crew would have had a good chance at recovery ... "
NOTE: Numbers for illustrative purposes ONLY. (This for the journos and gadflies who read here ...)
I will repeat, due to my belief on how important this is, that since the initial condition for recovery
"Mon dieu, those crickets were telling the truth, we are stalled!"
was NEVER encountered, the BEA cannot make a valid finding, and can do speculation rather than analysis.
What they can ask the industry to do is figure it out, which the industry might not do.
Getting those kinds of test points isn't just expensive, it can be dangerous to the flight crew, and may or may not be worth the money invested.
Based on what a number of sober and credible professional airline pilots and engineers (I do not include myself in that company) have contributed in these discussions, I suggest to you that chasing that set of data points has less expensive, less risky, and more pilot friendly alternatives.
I believe the BEA came to a similar conclusion.
Last edited by Lonewolf_50; 16th Jul 2012 at 13:57.