Originally Posted by
RetiredF4
You sure did notice, that we are discussing the "falling" here in this thread.
We're discussing the accident timeline as a whole, and that includes how the aircraft went from "flying" to "falling". Consequently Clandestino's point remains valid - if the PF had stayed within the envelope then there wouldn't be 8 pages (and counting) of discussion on the subject.
Also - I'm not talking A v B, except on the specific occasions when Boeing's FBW implementation has been brought up - and even then it's only to compare and contrast as opposed to being a fanboy for either. If I've been more prolific than I should be (and believe me that does concern me) then it has only been to answer the wilder theories that keep coming - we know journalists frequently peruse this site and I don't want misinformation showing up in the press during the slow news days of summer.
Originally Posted by
Lyman
Doze: Short question, one word necessary only. Is Overspeed protection active in Alternate Law 2 ?
No.
[EDIT : A "soft" Overspeed protection is available in Alt1, but it can be overridden by pilot input - if you're attempting to suggest that the PF got mixed up between Alt1 and Alt2, then I don't think it's likely - because the inputs made were sufficient to override the "soft" protection. ]
Originally Posted by
CONF iture
But you can still comment the following part, that’s where DozyWannabe is in difficulty :
You can permanently disable the autothrust function, and therefore lose Alpha Floor, but you can still maintain full back stick without stalling, IDLE thrust. The system will maintain Alpha Max for you - NO STALL - Going down YES - BUT NO STALL - STILL FLYING
I posted that exact functionality several times - no difficulty at all, and it's a feature - not a bug. However for that to work, the aircraft systems must be in Normal Law, and AF447 wasn't.
Also, the permanent autothrust disable command (hold down disconnect for >45s) is only intended for use in the case of erratic autothrust behaviour stemming from a failure - as far as I know this has never happened on the line.
[EDIT :
Originally Posted by
CONF iture
Stall is question of AoA not of thrust.
Did you see this (my bold)?
Originally Posted by
DozyWannabe
Now let's see - Alpha Max isn't a protection, it's a variable value indicating the maximum AoA an aerofoil can reach before it stops generating lift (this is simplified, but you catch my drift). AoA is determined by the coefficient of lift, the formula for calculating which includes airspeed/Mach as a variable.
The two ways of decreasing AoA are to reduce pitch and/or increase airspeed. If reduction of pitch is undesirable, the only way you can reduce AoA is to increase airspeed by increasing thrust.
So AZR is in fact correct in general terms. Airspeed (and by extension thrust) indirectly influence the AoA, but they are crucial factors in its determination.
]
I've got to say thanks to Clandestino - being a line pilot he can bring anecdotal experience from the line into the discussion in a way that I can't - and also has the clout to be more brutally honest than I feel I can get away with:
Originally Posted by
Clandestino
In the real world, achieving 17.9°pitch at cruise altitude when the target is 5° is not normal or tolerable. That it can turn out to be fatal is not news to some of us. Hopefully, most.
...
Protection activation is very serious safety occurrence and more often than not is bound to be investigated by the independent air safety investigative body, not just airline safety dept. In the first world, at least.
...
On Airbus, intentional activation of alpha prot by pulling full back stick is reserved only for GPWS or low level windshear escape and you have to do some pretty bad plan[n]ing or be once in a 10E4 lifetimes unlucky to get there.
...
We are looking at the three pilots who went into territories totally unknown to them, got thoroughly scared and managed to kill themselves and all on board through panicky reaction. How and how much did the aeroplane, regulators, airline and pilots themselves contributed to tragic inability to cope with minor malfunction is something that has to be resolved.