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Interesting. Thank you!...
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Of course. t's not an error on / off switch. But there are probabilities and frequencies involved. CFIT cans till happen with EGPWS. Mid-airs can still happen with TCAS. Yet, these technologies reduced A LOT the frequency of these accidents....
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I am going to be extreme and propose that, until someone figures a life-saving mistake-proof method or technology, only the tower in control on active runway can clear ANYONE to use that runway, be it take-off, land or cross.
In this way not only all the traffic using the runway will be coordinated by the same parson avoiding coordination mistakes between controllers, but also all the pilots using that runway would be in the same frequency so will have a chance to detect a now-more-unlikely mistake by the controller.
I acknowledge it is not very practical since that would require frequent frequency changes by pilots taxiing, but it is a small price to pay compared to having a 777 taking off into a crossing A350.
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What changed since your prime days to today? It is just my impression or we were not having anywhere near the amount of runway incursions back then? (especially ATC- caused ones)...
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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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