Hi BOAC,
Originally Posted by BOAC
Do we have any idea of the 'g' required for this pitch up into the climb? I see 1.75g quoted as an over-speed FCS 'increase' in applied PF input. Are we close?
Assuming that this aircraft overshoot Mach 0.86 (Normal Law), after an overspeed warning, with speed still increasing, an overspeed protection could have been ordered by the FMGC and could have added
up to 1.75 g pitch load while disconnecting the autopilot, hence, this would happen at 0210:05.
The main issue with such case is that the BEA/AIB/NTSB/etc. would perfectly know it from the beginning, right after the first CVR (warnings) and DFDR tracks (speed, etc.) lectures ; then they will voluntarily hide that to us...
Another issue is that it doesn't fit either with all the known flight conditions (~Mach 0.81 = 275 kt), neither with all the known (and clearly acertained) system faults at 0210:05 which are all linked with an Unreliable Airspeed event.
In fact, there is not a single doubt that this aircraft entered ALTERNATE 2 at 0210:05, right after an UAS check took place during the previous second (airspeed incoherence detected). It is acertained that the system confirmed the already applied ALT2 ten seconds later -> 0210:14/15; hence, it is also proved that it was not a transient fault, meaning that NORMAL LAW was lost for the remainder of the flight.
Consequently, from 0210:05, autopilot, autothrust, several systems/functions, and all the flight envelope protections were lost, excepted the envelope g-load factor protection that will limit the PF imputs into the range of -1 g to 2.5 g in clean configuration.