AF 447 Thread No. 9
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Originally Posted by CONF iture
To the contrary, the motion of the THS (most probably unoticed) makes all the difference between forcing on the stick or not.
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Re : ACARS printer position
Thank you, PJ2 and EMIT for respective picture and information.
You confirm the ACARS printer was just before the eyes of Marc DUBOIS when he came back in the cockpit... the first thing he could see !
You confirm the ACARS printer was just before the eyes of Marc DUBOIS when he came back in the cockpit... the first thing he could see !
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@rh:
Why would an airline captain, clearly arriving in the middle of an emergency, immediately go to the maintenance log printer and read the output?
Why would an airline captain, clearly arriving in the middle of an emergency, immediately go to the maintenance log printer and read the output?
Last edited by DozyWannabe; 16th Aug 2012 at 17:23.
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rh;
I'm not sure of the point being made here but just to be careful about drawing any conclusions from "the first thing he could see", there would not have been any ACARS printouts as a result of any of the generated maintenance messages or anything else, at that point.
You confirm the ACARS printer was just before the eyes of Marc DUBOIS when he came back in the cockpit... the first thing he could see !
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Originally Posted by HN39
Would you care to explain that? Difference in stickforce vs stick angle? Different airplane response to stick angle?
- During the controls check if a full deflection has to be maintained.
- During a deliberate protection activation in case of GPWS.
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CONF iture,
I don't see the relevance of (1) and (2) for the AF447 scenario.
IMO 1/5 of the full SS deflection demands a certain level of 'g' and the FCS will provide that irrespective of the THS position, as long it it doesn't need more than full elevator.
I don't see the relevance of (1) and (2) for the AF447 scenario.
IMO 1/5 of the full SS deflection demands a certain level of 'g' and the FCS will provide that irrespective of the THS position, as long it it doesn't need more than full elevator.
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Hazelnuts39
You seem to be falling into the simplistic trap of assuming the elevators and THS were behaving normally. They weren't. The airflow around them approximated to an M2-F1 flight more than anything.
Autotrim should have been disengaged as soon as there was a disagree, because it has to be protected in different ways for different flight regimes. If the flight system doesn't know where it is (alt, speed) then it cannot protect the THS rate and the THS will run away too far too fast, as it did, making the airplane unflyable.
Not for the first time, either.
I am not a pilot and have no qualification beyond a vaguely relevant degree. I never fly.
You seem to be falling into the simplistic trap of assuming the elevators and THS were behaving normally. They weren't. The airflow around them approximated to an M2-F1 flight more than anything.
Autotrim should have been disengaged as soon as there was a disagree, because it has to be protected in different ways for different flight regimes. If the flight system doesn't know where it is (alt, speed) then it cannot protect the THS rate and the THS will run away too far too fast, as it did, making the airplane unflyable.
Not for the first time, either.
I am not a pilot and have no qualification beyond a vaguely relevant degree. I never fly.
Last edited by mike-wsm; 16th Aug 2012 at 18:14.
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Studi
But that is a non-issue for me, as in alternate mode, the Airbus still protects you somehow, which is more than any conventional plane. For me any protection is better than no protection, as long as it does not wrongly protect. I think we can agree on that.
But that is a non-issue for me, as in alternate mode, the Airbus still protects you somehow, which is more than any conventional plane. For me any protection is better than no protection, as long as it does not wrongly protect. I think we can agree on that.
But would you please explain the bolding in the above sentence some more, especially with regard to AF447, as we are discussing that accident here? To be specific, autothrust is no protection in the sense of discussion here, and autotrim is just a feature to relieve the pilot of trimming without any force feedback under impementation of NZ law. I know there is load factor protection left, but others than that?
Last edited by RetiredF4; 16th Aug 2012 at 18:18.
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mike-wsm,
your understanding of the A330 flight controls is obviously different from mine. As I said, the THS position is important when the elevator is used to its maximum capacity. Otherwise it doesn't matter at all.
your understanding of the A330 flight controls is obviously different from mine. As I said, the THS position is important when the elevator is used to its maximum capacity. Otherwise it doesn't matter at all.
Last edited by HazelNuts39; 16th Aug 2012 at 19:03.
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Originally Posted by HN39
I don't see the relevance of (1) and (2) for the AF447 scenario.
Originally Posted by HN39
IMO 1/5 of the full SS deflection demands a certain level of 'g' and the FCS will provide that irrespective of the THS position, as long it it doesn't need more than full elevator.
No autotrim and it won't be 1/5 but anything up to full stick deflection in the target pursuit.
The BEA is not saying anything different except that for those 2 key paragraphs they avoid mentioning the word autotrim and they should have added to the end of the second one :
"It appears that this absence of positive static stability could have contributed to the PF not identifying the approach to stall and the aggravation of the stall."
Originally Posted by Final Report P187 en
When there are no protections left, the aeroplane no longer possesses positive longitudinal static stability even on approach to stall. This absence specifically results in the fact that it is not necessary to make or increase a nose-up input to compensate for a loss of speed while maintaining aeroplane altitude. This behaviour, even if it may appear contrary to some provisions in the basic regulations, was judged to be acceptable by the certification authorities by taking into account special conditions and interpretation material. Indeed, the presence of flight envelope protections makes neutral longitudinal static stability acceptable.
However, positive longitudinal static stability on an aeroplane can be useful since it allows the pilot to have a sensory return (via the position of the stick) on the situation of his aeroplane in terms of speed in relation to its point of equilibrium (trim) at constant thrust. Specifically, the approach to stall on a classic aeroplane is always associated with a more or less pronounced nose-up input. This is not the case on the A330 in alternate law. The specific consequence is that in this control law the aeroplane, placed in a configuration where the thrust is not sufficient to maintain speed on the flight path, would end up by stalling without any inputs on the sidestick. It appears that this absence of positive static stability could have contributed to the PF not identifying the approach to stall.
However, positive longitudinal static stability on an aeroplane can be useful since it allows the pilot to have a sensory return (via the position of the stick) on the situation of his aeroplane in terms of speed in relation to its point of equilibrium (trim) at constant thrust. Specifically, the approach to stall on a classic aeroplane is always associated with a more or less pronounced nose-up input. This is not the case on the A330 in alternate law. The specific consequence is that in this control law the aeroplane, placed in a configuration where the thrust is not sufficient to maintain speed on the flight path, would end up by stalling without any inputs on the sidestick. It appears that this absence of positive static stability could have contributed to the PF not identifying the approach to stall.
Last edited by CONF iture; 16th Aug 2012 at 19:03.
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But CONF, you're basing that assertion on a supposed sim experience you had where you could not get the nose back down. My sim experience (as well as other people's) seems to suggest differently.
You can't deny that you're less interested in safety than sticking one to Airbus and always have been.
You can't deny that you're less interested in safety than sticking one to Airbus and always have been.
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Originally Posted by Dozy
But CONF, you're basing that assertion on a supposed sim experience you had where you could not get the nose back down. My sim experience (as well as other people's) seems to suggest differently.
Originally Posted by Dozy
You can't deny that you're less interested in safety than sticking one to Airbus and always have been.
Originally Posted by Dozy
This is one of the reasons I get extremely vexed when I'm accused of "defending" Airbus.
But definitely you are a funny guy Dozy.
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Originally Posted by CONF iture
You are the one asking the ''difference in stickforce vs stick angle'' I just provide the exemple.
How will you get that certain level of 'g' if the autotrim does not cooperate but by pulling more on the stick ?
No autotrim and it won't be 1/5 but anything up to full stick deflection in the target pursuit.
No autotrim and it won't be 1/5 but anything up to full stick deflection in the target pursuit.
When the BEA note the absence of positive static stability in the Nz law, and how that may have affected the pilot's perception, it is not about autotrim because that is irrelevant in that context.
EDIT:: The Nz law can be used in an airplane like the F-16 with an all-flying-tail, or theoretically with a non-trimmable stabilizer.
Last edited by HazelNuts39; 16th Aug 2012 at 20:08.
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Picking on DW again
But CONF, you're basing that assertion on a supposed sim experience you had where you could not get the nose back down.
You can't deny that you're less interested in safety than sticking one to Airbus and always have been.
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HN
My question was how the THS affects the stickforce vs stick angle. You wrote: "Displacing the sidestick is like fighting a spring, the further you go the heavier it becomes." That is correct, and doesn't change due to THS movement.
I will need some clarification of that statement? Because the effect of the elevators can be extremely different on the airframe, depending on the Pitch of the HS.
My question was how the THS affects the stickforce vs stick angle. You wrote: "Displacing the sidestick is like fighting a spring, the further you go the heavier it becomes." That is correct, and doesn't change due to THS movement.
I will need some clarification of that statement? Because the effect of the elevators can be extremely different on the airframe, depending on the Pitch of the HS.
Last edited by Lyman; 16th Aug 2012 at 20:51.
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Studi
Now what do it mean with alternate law protects you somehow. Depending on the failure, Alternate Law has not only load factor protection, but also high and low speed stability. Low speed stability induces a nose down moment if you get too slow, however can be overriden with the stick (not possible in normal law). Same with high speed stability. However, in daily ops, I don't need to know that I have it, as I am not supposed to use it deliberately. If it helps me, fine, that is my advantage, if not, I am as bad as in a conventional plane.
Now what do it mean with alternate law protects you somehow. Depending on the failure, Alternate Law has not only load factor protection, but also high and low speed stability. Low speed stability induces a nose down moment if you get too slow, however can be overriden with the stick (not possible in normal law). Same with high speed stability. However, in daily ops, I don't need to know that I have it, as I am not supposed to use it deliberately. If it helps me, fine, that is my advantage, if not, I am as bad as in a conventional plane.
Maybe i should have quoted the whole sentence of you. (bolding by me)
That is why it leaves normal law and enters alternate law, and that is why alternate law has in itself different levels of protection. But that is a non-issue for me, as in alternate mode, the Airbus still protects you somehow
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Lyman,
The stickforce characteristic is shown here.
The loadfactor versus SS deflection is shown here.
The point is that to hold the stick at 20% of full travel requires a certain force, and that 20% deflection of the SS commands a certain loadfactor, whatever the THS position is. If you have any more questions, please be more specific.
The stickforce characteristic is shown here.
The loadfactor versus SS deflection is shown here.
The point is that to hold the stick at 20% of full travel requires a certain force, and that 20% deflection of the SS commands a certain loadfactor, whatever the THS position is. If you have any more questions, please be more specific.
Last edited by HazelNuts39; 16th Aug 2012 at 21:30.
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Why the crew couldn't solve the problem?
Earlier on in this thread one poster said
"Sadly, the (non adequately trained) crew of AF447 were:-:
Surprised by the System output and worse: Had to process garbage generated by the System. And failed in their decision making. Actually, worse than that, never realizing (in time) what was going on..."There has to be some reason for this.
OK, some of the crew might have been relatively inexperienced or under-trained but they certainly weren't stupid. They were bright, skilled and well-qualified. Yet somehow they just couldn't get their heads around what was happening to their aircraft .Could their thinking-power have been impaired by breathing insufficient oxygen?. Has anyone even bothered asked the question?.(.Exactly the point I was trying to make in the “SLF” thread "Can Pilots REALLY concentrate at 35,000 feet?". We know that none of the crew of AF447 had done what they really needed to do - don oxygen masks.
Their blood oxygen levels after four hours at 35,000 feet would have been severely depleted. They wouldn’t have been aware of it. Most pilots aren’t. They could still perform the mundane routine stuff just fine - most crews can. But in all probability is was simple lack of oxygen that prevented them from firing up the extra brainpower they desperately needed to get them out of the aeronautical elephant-trap they were falling into.
Chief investigator Alain Bouillard says that the pilots simply needed to “properly react” to in-flight circumstances. “When it comes down to it, safety will always be based on the capacity of the pilots and the signals which they are given, which they have to understand and react to,” he said.
He’s right - but if you feed pilots air at a cabin altitude of 8000 feet (much lower in oxygen content than air at a real altitude of 8000 feet) then when the chips are down crews will make mistakes - and they did.
"Sadly, the (non adequately trained) crew of AF447 were:-:
Surprised by the System output and worse: Had to process garbage generated by the System. And failed in their decision making. Actually, worse than that, never realizing (in time) what was going on..."There has to be some reason for this.
OK, some of the crew might have been relatively inexperienced or under-trained but they certainly weren't stupid. They were bright, skilled and well-qualified. Yet somehow they just couldn't get their heads around what was happening to their aircraft .Could their thinking-power have been impaired by breathing insufficient oxygen?. Has anyone even bothered asked the question?.(.Exactly the point I was trying to make in the “SLF” thread "Can Pilots REALLY concentrate at 35,000 feet?". We know that none of the crew of AF447 had done what they really needed to do - don oxygen masks.
Their blood oxygen levels after four hours at 35,000 feet would have been severely depleted. They wouldn’t have been aware of it. Most pilots aren’t. They could still perform the mundane routine stuff just fine - most crews can. But in all probability is was simple lack of oxygen that prevented them from firing up the extra brainpower they desperately needed to get them out of the aeronautical elephant-trap they were falling into.
Chief investigator Alain Bouillard says that the pilots simply needed to “properly react” to in-flight circumstances. “When it comes down to it, safety will always be based on the capacity of the pilots and the signals which they are given, which they have to understand and react to,” he said.
He’s right - but if you feed pilots air at a cabin altitude of 8000 feet (much lower in oxygen content than air at a real altitude of 8000 feet) then when the chips are down crews will make mistakes - and they did.
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Korrel
OK, some of the crew might have been relatively inexperienced or under-trained but they certainly weren't stupid. They were bright, skilled etc
I don't think the training records of the two F/O's are in the public domain.
We know that none of the crew of AF447 had done what they really needed to do - don oxygen masks.
Their blood oxygen levels after four hours at 35,000 feet would have been severely depleted
I've been sat there at 33000 ft and lost the 'cabin' - then I put on the oxygen mask and decended.
Korrel, with all due respect, I think you have failed to notice one or more 'elephants in the room'.
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He’s right - but if you feed pilots air at a cabin altitude of 8000 feet (much lower in oxygen content than air at a real altitude of 8000 feet) then when the chips are down crews will make mistakes - and they did.
