Originally Posted by Lonewolf_50
HazelNuts39, is the pitch angle trace in figure 3 from the FDR released info (so far)? How confident are you of pitch angle to timeline synchronization for your graph?
The traces are mutually consistent. They are derived from the assumed vertical acceleration as described. It's an iterative process: assume az/g, look what trajectory and speeds it produces, and how that fits the BEA description. Then modify the az/g to improve the 'goodness of fit' in several iterations, until you're satisfied it is good enough to give a reasonable description of the probable course of events. It's a bit like straightening a table cloth, you pull one corner to flatten a wrinkle, and get more wrinkles in other places, except this has more degrees of freedom. Confidence is a function of 'goodness of fit' in the few corners that BEA gave us. An important caveat that I should have mentioned is that the available cL-alpha data cover only the operating envelope as limited by buffet onset (alpha-max). Everything beyond that is 'educated guess' or pure conjecture.
Originally Posted by sensor_validation
Is it possible to deduce from your great graphs at what point the zoom climb becomes 'ballistic'? Strikes me that a some point before the apogee airspeed and pitch wouldn't be be able to generate enough lift for level flight - and the only way out would have been a carefully managed pitch down and controlled descent past the apogee. Was FL375 @ M0.68 sustainable? Guess need to make assumptions about engine thrust and response time if not already full.. At what point on your graphs was/should the stall warning be triggered?
It was never clear to me exactly how the A340 airprox zoom climb was successfully recovered - pilot or AoA protection avoiding the stall warning using full thrust and pitch down?
The zoom climb is partially ballistic whenever 'gee' is less than one. The only way out is to reduce AoA below that at which the stall begins, and that is achieved when stall warning stops (except when IAS<60 kts). Airspeed and thrust are for later. Lift-wise FL375 @ M0.68 is sustainable, but to sustain airspeed the airplane must be put on a descending path (perhaps TOGA would maintain speed in level flight - I don't know). The stall warning threshold is the red dotted line - with valid IAS. BEA has explained the reversion when UAS, but that explanation has been put into doubt because it doesn't fit the Air Caraibes and other UAS incidents.(*)
IIRC in the A340 airprox zoom climb pilot action on the sidestick took the system out of High AoA protection, and the airplane would then recover itself stick-free.
(*)Note: A poster has suggested that in case of airspeed becoming invalid, the stall warning threshold is based on the last valid airspeed, rather than a low-speed value. In my mind, that makes more sense than BEA's explanation. So perhaps you should replace the dotted line in my graph by a horizontal line from the time of A/P disconnect.
PS:: My advice is to look at those traces qualitatively, and not to expect an angle to be accurate within a tenth of a degree.