Originally Posted by HarryMann
Wouldn't you need to know exactly how deep was the penetration of the sea surface? Have we any information on 'compliance' at water surfaces in these cases.
Indeed. As I set up two sides of the equation to get the units to match, I realized that I didn't have a figure for deceleration, and more explicitly, a time from V max to V zero. So I was dead in the water. (No pun intended).
Originally Posted by Machinbird
From my recollection, he described stall behavior of these aircraft as a low frequency vibration with increasing motion on the flight deck until it reached the point that was mandatory that the crew be strapped in or else they would be thrown from their seats. This type behavior would likely be also relevant to the A332.
Thanks. I'll have a listen to the link this weekend, over a coffee or two.
Originally Posted by Bergerie1 (#3473)
I relate all this because of the discussion in previous posts about whether the pilots could have distinguished between pre stall buffet and the turbulence associated with thunderstorms. I think the answer is in most cases 'yes', the two are distinguishable. However, in heavy turbulence it is highly probable that the pre stall buffet would be 'lost' in the general ambient turbulence.
And in really heavy turbulence one's brains feel rather 'scrambled' which would make it even more difficult! In which case it is quite possible that the pilots on AF447 would not have been able to discern the pre stall buffet.
Many thanks.
techgeek, if I may critique your presentation:
Originally Posted by techgeek
The A330 stall recovery procedure is to apply takeoff thrust and full aft stick, relying on the computer to maintain maximum allowable AOA.
If you stall, you have already exceeded max allowable AoA, yes?
If I am correct in understanding how pilots are trained, what you are calling stall recovery is actually recovery from approach to stall, then full power and Max Allowable AoA ... which will keep you from stalling, and get you out of near occasions of stall.
Once you actually stall, you have to REDUCE AoA (or you will remain stalled) which probably can't be done with aft stick, unless you are flying inverted ... which I don't think you'll find people doing in the A330.
You appear to have mixed and matched stall recovery and stall prevention.
Without FBW, no pilot uses full aft stick to recover from a stall (this is usually reserved for entering a spin!).
Agreed, however, I don't think you are correctly interpreting what the procedure is to be applied to.
This practice is unique to an aircraft with FBW and essentially puts the pilot in a position of relying on the computer to prevent the stall (because the pilot's control input is actually trying to cause the stall).
Stall prevention and stall recovery are not the same thing.
Do you see from the bolded bits why I think you are mixing apples and oranges?
More to the point, I disagree with your assertion that using max power and high (but not stalled) AoA is confined to FBW aircraft.
I used to teach a recovery from an approach turn stall (practiced at altitude, gear and flaps down) in which you deliberately enter a stall in a balanced turn, and you then ...
lower the nose (AoA) and level the wings
max power
raise nose to high AoA
eventually establish a rate of climb
I also used to do the following in the landing pattern to test stall prevention on safe for solo checks:
I'd hit the AoA test button briefly, to get the rudders to shake. In that training plane rudder shakers (like stick shakers in some commercial transport aircraft) was a warning of impending stall (AoA at about 26 units, stall typically at 29 units) . I would look for the following response (stall prevention): wings level, full power, climbing attitude ... with the idea being that if your approach to landing was close to stall, it was time to wave off (go around) and try again.
HazelNuts pointed out a few posts back that if AF 447 were stalled, the A330's robot voice would have been advising the pilots (with annoying repetition) that they had stalled. So my concern about "would they recognize the stall," and Bergerie1's point about what heavy turbulence might do to body senses, have already been answered by the aircraft's designers by using AoA to trigger "You are stalled!!!!" warnings in unambiguous terms. You'd think that
stall recovery would begin with a move to reduce AoA, yes? The FDR's will hopefully tell us if that is true or not, in due course.
[/QUOTE]
Originally Posted by bia botal (#3480)
Theres another scenario to consider then isn't there,
that the aircraft was turning,
perhaps they considered the best way out of a storm cell that they didn't know was there is the way they came in,
a turning aircraft with the handling pilot trying to reduce speed (my note: why trying to reduce speed? Turbulence/CB penetration considerations?)
that appears not to be whilst the aircraft is descending due to downdrafts may have been attempting to trade off speed to maintain some height, only speed is not reducing,
with thrust at idle, (my note: why thrust at idle?)
nose attitude high, (my note: why nose high?)
severe turbulence, and bank angle,(perhaps exaggerated by turbulence)
how long to stall now?
You posit a flight crew putting the engines at idle and trying to maintain altitude with the stick. Why? If the engines are at idle due to a failure or ice or something, would not the crew be cued, and would not the crew maintain airspeed and in descent try to get the engines started again? I'd think that is covered in training, and as noted previously, this was not a rookie crew.
Your event chain leaves me scratching my head.