Yes, I was thinking the same thing. Any plane can have catastrophic failures. A total loss of all electric systems would kill you in any modern plane. Not to mention the explosion of the center wing tank. The question is how extremely unlikely it is.
Seeing how fatal accidents where the pilots could not have saved it almost never happen, and how fatal hull losses happen at a rate of about 1 every 10 million take-offs for all types, FBW or not, Boing, Airbus or other, I think we are in the good way. In particular, the original A320 and the 737 NG are exactly equal in this metric.
Page 10 - https://www.boeing.com/content/dam/b...df/statsum.pdf...
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I am not sure if it would have not made a difference since the pilot was pulling fully back anyway. This nose down command (to simulate what happens in non-FBW plane when entering in ground effect, and to stimulate the pilot to pull up to flare) is jut a bias, not a "hard input" (i.e. not like alpha max) so it can be overridden with control inputs....
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Well, they had to, given other decisions that were made: make the pass at V-alpha-prot. That was never going to work with Alpha floor active.
So for me the real question is who's bright idea was to palan the pass at V-alpha-prot.
They could have decided to do the pass at VLS instead. Then:
- They wouldn't have needed to disable Alpha floor.
- They could have done the pass on autothrottle which would have avoided the inadvertent loss of speed below the target speed.
- They would have had more energy margin overall (for example, to pull up to avoid trees).
- The pass would have been just slightly less impressive, the difference was not worth the risk (yeah, I know, hindsight).
I think it was because it is inhibited below; 100ft you don't want the warning during the flare. Also at some point (too late) they firewalled the thrust lever which also inhibits the warning because you already took the corrective measure.
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Alpha floor. Since they intended to do a very slow pass (at V-alpha-prot, which is below VLS, and hence has to be manually maintained since you cannot select a speed below VLS in the autothrust), and V-alpha-floor is just a hair below V-alpha-prot, they disabled alpha floor to avoid that the FBW sets TOGA and ruins the low/slow pass. That was a big factor, because they allowed the plane to go well below the intended V-alpha-prot, which the alpha-floor protection would have not allowed, and hence they didn't have airspeed to pull up.
The chain of factors were:
- The pass was intentionally done on a runway that was not the one they planned and briefed (so nobody assessed the trees as a factor)
- Alpha floor disabled (intentionally and as planned and briefed)
- Airspeed inadvertently allowed to go well below the alpha prot intended target.
- Altitude inadvertently allowed to reduce well below the 100ft target.
- Engines at idle (because they were...
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I an Airbus plane in direct law, if the FBW decides to lower the nose because you reached alpha max, what you do with the sidestick is not really important. The plane will do what FBW says, not what the pilot right or wrong wants. And this feature has already saved lives.
Note the if....
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Not sure what you mean with "Alpha max pitch would be reduced", I would just say that alpha max (the AoA, not any particular pitch) would be achieved or exceeded and then yes, the FBW would subsequently command an AoA reduction which in this case would most likely result in a pitch reduction , in normal law.
I am trying to be careful with my selection of words. I explained in my old stall rant thread how a pilot can reduce the AoA (which involves "pushing down" or, more accurately, reducing back pressure on the control column) while at the same time the climb gradient, climb rate and pitch all increase. The reason why this can work is also the basic reason why the old and very inadequate approach to stall recovery procedure (TOGA and pitch 10 deg) still worked most of the times.
Yeah, I don't know either.
I don't what triggered it, but I also suspect manual input....
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#1 I think the nose-doen was pilot-commanded. I am just wondering if I may be wrong and if it may have been an FBW prot instead. I don't think so but still.
#2 I am not sure if the max AoA happens when the tail almost hits the runway. It looks to me like the pitch keeps increasing a bit more after lift off, but hard to tell with the change in perspective.
#3 Tailwind doesn't change the AoA.
#4 Wake turbulence can perfectly hit at those altitudes with horizontal and vertical components. As I mentioned earlier, wake turbulence due to a plane taking off or landing in the crossing runway would cause vertical and head-tail gusts, rather than roll. It happened before.
#5 Read #1 again.
https://www.youtube.com/watch?v=Kle80KB_s3I
https://www.youtube.com/watch?v=TEjbg_2yuFI...
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Alpha protection will do what it takes to keep alpha below alpha max. If it takes pitching down, pitching down it will.
Imagine a situation where you start to climb and achieve a pitch of say 10 degrees with 5 degrees of flight path slope (that's 10 degrees of deck AoA) and you are suddenly hit by a tailwind which reduces lift and the plane stops climbing but the pilot kept the 10-degrees pitch, now the plane has 10 degrees of deck AoA which could be past the alpha max threshold.
Not saying that that is what happened. Just in theory....
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Edelweiss almost touches down again immediately after lift-off
This is going to be an interesting one...
I don't know what the if anything crew did wrong (they might be the cause for this incident), but they seem to have done a few things right: Avoid a tail strike, and lower the nose to gain airspeed when the plane was not climbing (or was that an FBW AoA protection?).
They reported a tailwind on rotation, but that seems unlikely to me (at least a "normal" tailwind). The wind seems too calm and not gusty (look the smoke of the chimney). Maybe wake turbulence form an airplane landing or taking off on the crossing runway. While wake turbulence in trail tends to roll the airplane, wake turbulence at 90 degrees creates head/tail wind gusts as well as up/down drafts.
https://www.youtube.com/watch?v=jRNmwiB1oiQ...
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Not even that. They don't mention any psychological analysis whatsoever. Whether there was non or there was but they elected not to mention it....
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