American Airlines Flight 742 "flight control system" problems
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Originally Posted by Owain Glyndwr
Well one needs to exceed the alpha-protection threshold to trigger alpha-protect mode doesn't one?
The principle of alpha-protection is well documented though, and it is difficult (for a non-pilot) to see what practical use could be made of a knowledge of the actual numbers since as we all know, AoA is not displayed to the pilot.
Time after time incident/accident reports provide bits of values and this make much more interesting readings than the FCOM to comprehend the System you're working on.
Agreed that if he could have pulled to another 2 deg he could have reduced his vertical speed, but the fuselage crushing loads have two components, one of which is speed/AoA dependent so it is not obvious he would have been significantly better off.
Can you please point me to a reference for that statement? It is not how I understood the system.
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The pilots aren't "requested" to do anything - they can handle it as they see fit. The *system* is designed such that in Normal Law (i.e. in excess of 99% of the time), it is possible to command full stick deflection without risking the aircraft's stability. You can even pull at 67 degrees of bank to tighten the turn if you wish.
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The Airbus performed as designed in the Hudon crash. The B737 would have done better because they could have got another degree of pitch to make the splashdown perfect. The Sully splashdown was just fine however.
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You do make me smile, bubs. Judging by all the data I've been given on the subject, the difference would have been utterly negligible - and that's without taking into account what having the empennage in contact with the water for longer (as a consequence of increased pitch attitude) might have done to the structural integrity.
I've long since been resigned to the idea that CONF iture is going to tilt at his windmills no matter what he's told or by whom.
I've long since been resigned to the idea that CONF iture is going to tilt at his windmills no matter what he's told or by whom.
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Originally Posted by Dozy
In what context?
and that's without taking into account what having the empennage in contact with the water for longer (as a consequence of increased pitch attitude) might have done to the structural integrity.
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That's a GPWS warning - not specific to Airbus. And while - everything else being OK - the PF of a FBW Airbus *can* slam the stick against the back stop with little negative impact, that doesn't mean that they necessarily should.
That's not what I'm saying - I agree with Owain Glyndwyr that the recommended pitch of 11 degrees is dependent on other parameters being within a certain range and cannot be taken in isolation. There are far too many other variables involved to draw a conclusion on whether a difference the flare would have made any difference, either positive or negative.
Advise Airbus they have it wrong with the recommended attitude.
Originally Posted by sevenstrokeroll
and tell us of the PW engine on the king air?
When it comes to carrying 100+ people over mid and long ranges, there is no viable alternative to short-inleted turbofan and there is no way to protect them from birdstrikes.
Originally Posted by sevenstrokeroll
you must account for more than basic suck, squeeze bang blow
Originally Posted by bubbers44
I know I am prejudiced against Airbus but still am happy I never had to fly one. One happy Boeing pilot
Originally Posted by sevenstrokeroll
boys and girls...its been an interesting thread.
Originally Posted by sevenstrokeroll
IF you are good and lucky, I'll take a DC9 or 737 (prefer DC9). If you are average, maybe an airbus might be better...
Originally Posted by CONFiture
I am usually the one to question the Official Reports ...
Originally Posted by CONFiture
If you obtain the recommended attitude for ditching and reduce your vertical speed at impact in the meantime it is a simply a win win situation for the fuselage and the passengers.
Originally Posted by CONFiture
Clandestino has some difficulty to grab that point.
Originally Posted by bubbers44
The B737 would have done better because they could have got another degree of pitch to make the splashdown perfect
Originally Posted by CONFiture
Advise Airbus they have it wrong with the recommended attitude.
Originally Posted by Dozy Wannabe
And while - everything else being OK - the PF of a FBW Airbus *can* slam the stick against the back stop with little negative impact, that doesn't mean that they necessarily should.
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Originally Posted by Clandestino
Where would you get your additional attitude as aeroplane was already at 13° AoA and engines were not producing power?
2 additional deg of attitude to improve the touchdown.
Engine thrust is irrelevant.
I'd suggest renting out a C-172 with instructor and asking him to demonstrate slow flight, culminating in a couple of stalls would help in understand just how usable are last couple degrees of AoA before stall. It's not much.
Airbus doesn't care if some anonymous poster at some anonymous forum thinks they are wrong, especially if such a belief comes from his inability to understand the basic aerodynamics.
You can't have optimal attitude with optimal RoD if you are below optimal speed.
You wouldn't flare at 1000 feet would you ?
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Originally Posted by Dozy
That's a GPWS warning - not specific to Airbus. And while - everything else being OK - the PF of a FBW Airbus *can* slam the stick against the back stop with little negative impact, that doesn't mean that they necessarily should.
What's your experience again ?
There are far too many other variables involved to draw a conclusion on whether a difference the flare would have made any difference, either positive or negative.
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now I am sure there are a number of non airline pilots talking out their APU exhaust.
I've seen too much and too much misunderstanding. It is almost too much...
But I do wonder about the S like ducting in a 727 and how a bird might be ripped apart prior to hitting the fan.
I do wonder about people who are looking for a time that stalling a plane or banking very steeply might not be used
And when someone has the lack of understanding to project incorrect speeds in one type vs another...I quake.
so, fly your airbus just as the computer says. Hal will take good care of you. Ask the Air France boys! And waiting for the computer to reset after an upset...oh yeah!
It boils down to this...a pilot must be able to fly the wings off a plane in order to save it...and if the computer says no, you might as well not have a pilot on board.
And, for those brilliant ones here, Seeing the vulnerability of a large fan inlet vs a smaller one and just LUCK in the exact position of a bird vs the inlet at any time, considering the spacing of birds in formation...well, you believe what you want. Prove me wrong...take a plane up into a formation of birds...video it and see exactly how the birds might react to a fuselage vs just an inlet...do it with a number of aircraft types and report back.
All those who have flown transports out of LGA, raise their hands.
! = hand raise
others , need not apply.
I've seen too much and too much misunderstanding. It is almost too much...
But I do wonder about the S like ducting in a 727 and how a bird might be ripped apart prior to hitting the fan.
I do wonder about people who are looking for a time that stalling a plane or banking very steeply might not be used
And when someone has the lack of understanding to project incorrect speeds in one type vs another...I quake.
so, fly your airbus just as the computer says. Hal will take good care of you. Ask the Air France boys! And waiting for the computer to reset after an upset...oh yeah!
It boils down to this...a pilot must be able to fly the wings off a plane in order to save it...and if the computer says no, you might as well not have a pilot on board.
And, for those brilliant ones here, Seeing the vulnerability of a large fan inlet vs a smaller one and just LUCK in the exact position of a bird vs the inlet at any time, considering the spacing of birds in formation...well, you believe what you want. Prove me wrong...take a plane up into a formation of birds...video it and see exactly how the birds might react to a fuselage vs just an inlet...do it with a number of aircraft types and report back.
All those who have flown transports out of LGA, raise their hands.
! = hand raise
others , need not apply.
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Is it directed to Dozy, he's the one to think that the recommended attitude for ditching by Airbus might do something to the structural integrity.
It also shows that in case of water impact with an aircraft pitch below ≈ 8°, or above ≈15° major airframe structural breakage is expected.
11 deg is nearly in the middle of that range, but departure away from that optimum on either side is bound to have a bad effect, although it is very possible that for reasonably small deviations the effect is not large (nonlinear characteristics).
Last edited by Owain Glyndwr; 27th Mar 2013 at 16:30.
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Point of order - I'm not saying anything about the recommended pitch attitude causing structural damage, I'm echoing Owain's earlier assertion that the recommended pitch attitude applies only when other parameters are met (which in that case they were not).
The damage to the aft fuselage skin could just has easily have been caused by impact with solid floating debris on the river - in fact given that the pitch attitude was within the recommended limits that Owain posted above, it gives some credence to the idea. Of course there's no way of definitively proving it one way or the other, so IMO it's pointless arguing the toss at this point.
Quite what this has to do with the OP is anyone's guess.
The damage to the aft fuselage skin could just has easily have been caused by impact with solid floating debris on the river - in fact given that the pitch attitude was within the recommended limits that Owain posted above, it gives some credence to the idea. Of course there's no way of definitively proving it one way or the other, so IMO it's pointless arguing the toss at this point.
Quite what this has to do with the OP is anyone's guess.
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Saving some airspeed to make the final touchdown as flat as possible and at the right attitude is important In all types of aircraft if you have no problem with space available to land which they didn't. Some people here say they were 15 knots slow on descent. Looking at the video of the touchdown it didn't look like they had a high descent rate starting their flare. With no power and 15 K slow I know how my landing would be.
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It wouldn't be as good as it would have been had you flown the correct speed and had excess energy and nose authority to flare with.
See your still struggling to accept the FDR traces, NTSB and Airbus ref the descent rate at touchdown.
See your still struggling to accept the FDR traces, NTSB and Airbus ref the descent rate at touchdown.
Last edited by Ashling; 28th Mar 2013 at 00:07.
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Obviously you cannot maintain700 fpm with no power without a lot of additional airspeed to flare. They seem to have splashed down normally in the video. If anyone can show data below 50 ft please post it. Above 50 ft with no power doesn't mean much with no power.