With the ongoing discussion over the what the crew may have heard, seen or felt in the stalled environment, I believe the following should be noted:-
- Once stalled the AoA was never less than 35° and finished at 61°
- Pitch attitude was 16°NU at stall and at end of flight, though occasionally less
- Aerodynamic flow was abnormal/turbulent
- Likelihood of rain/hail striking cockpit windows was low
- Buffet vibration generated around wings and engine pods complete with noise
The overall effect may have been perceived as a Vmo/Mmo event. That of course doesn't explain exactly how the aircraft was delivered into that situation in the first place.
Taking a step back from the UAS upset, it is worthwhile noting that the flight plan provided for a climb to FL370 at SALPU. The forecast OAT at FL350 between ORARO and TASIL was -46°C, but with their weight of 205 tonnes and high OAT, that higher level request wasn't made to ATLANTICO.
"the little bit of turbulence that you just saw
[…] we should find the same ahead […] we’re in the cloud layer unfortunately we can’t climb much
for the moment because the temperature is falling more slowly than forecast"
Add
ITCZ to the bolded comments above, plus an OAT value probably warmer than forecast, and you have a receipe that should have "rung a few bells" - but it didn't.
In the AF447 Thread on 27 September 2009 I wrote, "Icing that took place was probably
'rapid' as opposed to 'gradual'".
Following the AP/ATHR disconnect, the aircraft entered a "zoom climb". The Stall Warning sounded briefly during the pitch up manuever and some ND inputs were made and attitude was reduced to 7°NU but the AoA was still rising and the SW sounded again. Further NU inputs prevented any normal stall recovery and once the CAS became less than 60KTS the SW stopped.
As I stated over 2000 posts ago, the software needs to be changed to sense both the CAS and AoA direction of change and the effect of NCD values to provide an unambiguous "
STALLED!" warning on the PFDs. There should be no need for the "big red button" marked "SOS", because if there is, it is only a cover-up for lack of training and/or understanding by those charged with the safe flight of the aircraft and all those souls onboard.
Also posted many moons ago was a suggestion that once a UAS event at cruise altitude is detected, that the AP/ATHR combo continue in a NORMAL 2 LAW where pitot dynamic/static related inputs are replaced by IRU data and a pseudo CAS is provided to the AP. This will also cover the 300 foot static baro loss often noted in these events, and with due warning to the crew enable them to monitor the situation and oversee that NORMAL 1 LAW is resumed when ADRs are in agreement.
You can, "Lead a horse to water, but you can't ....... "
Notwithstanding, there may also be some underlying physiological related events which will no doubt surface in the Final Report.