AF 447 Thread No. 5
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The acars message said the pitot system failed causing AP and AT to disengage probably because of their recurring icing problem. Any speculation about weather other than icing taking the plane down needs to be proven. So far there is no evidence of that being the problem since none of the other flights with normal deviations had a problem.
Those who insist it was turbulence and flying into a thunderstorm that caused the accident have absolutely no proof and are speculating. We know BEA knows exactly why they crashed by now. When they write the report we will know too. Be patient.
Those who insist it was turbulence and flying into a thunderstorm that caused the accident have absolutely no proof and are speculating. We know BEA knows exactly why they crashed by now. When they write the report we will know too. Be patient.
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Cbs
When sitting my F/Nav. examination, one of the questions was " You are the Chief Navigator of a Trans Atlantic Airline. What radio equipment would you require and why?"
I specified pretty well everything...
I asked another candidate what he had replied. He said that he had written " I have been in this position myself. I would require 2 ADFs. Two for reliabilty. With them I could get time checks for Astro. I have flown across the Atlantic 90 times with just this equipment and am quite satisfied with it." ( He had held this position with a South American airline. This would have been pre Weather radar being around.)
It might be helpful to look at what had happened to some of the other airlines' experiences with loss of airspeed. NWA, near Tokyo were some 25 miles from a Cb which was off to one side and went into some cirrus. It was daylight. I think that they lost their Pitot etc on two occasions in quick succession, both recovered in a few minutes. TAM was over the Caribbean, at night. Again the ASI came back after a few minutes. Both of the flights were prior to AF. Jetstars episode came after AF.
More details must be available of these (and others ?) from places other than my armchair.
What went right ? ( for them)
I specified pretty well everything...
I asked another candidate what he had replied. He said that he had written " I have been in this position myself. I would require 2 ADFs. Two for reliabilty. With them I could get time checks for Astro. I have flown across the Atlantic 90 times with just this equipment and am quite satisfied with it." ( He had held this position with a South American airline. This would have been pre Weather radar being around.)
It might be helpful to look at what had happened to some of the other airlines' experiences with loss of airspeed. NWA, near Tokyo were some 25 miles from a Cb which was off to one side and went into some cirrus. It was daylight. I think that they lost their Pitot etc on two occasions in quick succession, both recovered in a few minutes. TAM was over the Caribbean, at night. Again the ASI came back after a few minutes. Both of the flights were prior to AF. Jetstars episode came after AF.
More details must be available of these (and others ?) from places other than my armchair.
What went right ? ( for them)
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Frames of reference
Dutch M
Hi,
I don't really want to discourage an ambitious attack on the AF447 energy question, but let me add a few additional questions to your approach for an answer.
Have you added in the Earth's velocity vector around the Sun? How about the velocity of the solar system around the Milky Way galaxy? The answer should be that it is not necessary, these are negligible factors. For the same reasons, the rotation of the earth does not need to be included (unless you are flying ballistic like an ICBM). It exerts a force on the aircraft all right. We call it Coriolis force, but that too is negligible for our purposes.
There is no absolute inertial frame of reference then, is there? The height gain only reflects the change in position relative to the Earth's center of mass.
Will an aircraft flying 100 knots into a 100 knot head wind be able to convert some of that velocity into altitude gain? Of course it can. (Assuming it can fly slower than 100 knots)
So when doing the Ekin calculations properly, around 3 times more Energy
becomes available for height gain. Note: Speeds only intended for example
purposes, these aren't the actual AF447 figures.
becomes available for height gain. Note: Speeds only intended for example
purposes, these aren't the actual AF447 figures.
I don't really want to discourage an ambitious attack on the AF447 energy question, but let me add a few additional questions to your approach for an answer.
Have you added in the Earth's velocity vector around the Sun? How about the velocity of the solar system around the Milky Way galaxy? The answer should be that it is not necessary, these are negligible factors. For the same reasons, the rotation of the earth does not need to be included (unless you are flying ballistic like an ICBM). It exerts a force on the aircraft all right. We call it Coriolis force, but that too is negligible for our purposes.
There is no absolute inertial frame of reference then, is there? The height gain only reflects the change in position relative to the Earth's center of mass.
Will an aircraft flying 100 knots into a 100 knot head wind be able to convert some of that velocity into altitude gain? Of course it can. (Assuming it can fly slower than 100 knots)
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Dutch M
HN39 has done an energy matching simulation (segment by segment) combined with aerodynamic assumptions. (Believe it was in the prior Tech thread.) His conclusion was that the final climb from FL375 to FL 380 was ballistic, i.e. the aircraft started upward on the last dregs of its lift and decelerated below actual level flight stall speed in the climb. This would allow the aircraft to fly below actual level flight stall speed and continue trimming nose up because the AOA had not yet become high enough to shut down the automatic pitch trimming. When gravity caught up with the aircraft and it began to fall, it then went rapidly well past the stall AOA and shut down the automatic pitch trim at 13 degrees ANU.
HN39 is very good with this type of thing, and we Physics duffers should respect his knowledge.
HN39, if I have gilded the Lilly too badly please correct me.
The implications of the above, is that, in case the aerodynamics is
different as expected, the airplane can be stalled, without the
stall warning being triggered.
different as expected, the airplane can be stalled, without the
stall warning being triggered.
HN39 is very good with this type of thing, and we Physics duffers should respect his knowledge.
HN39, if I have gilded the Lilly too badly please correct me.
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Originally Posted by takata
Hence, from this point, ALT2 without valid airspeed/Mach and SPEED LIMIT FLAG on PFD make it quite certain that Low and High Speed Stabilities were NOT available.
Originally Posted by First interim report P52
Note: the alternate 2 control law is a load factor law for pitch and a direct law for roll. Only the load factor protection remains available. In certain cases, the high and low speed stabilities may also be lost.
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Dutch M The A330 is layed out nose heavy
and with stalled main wings the residual main wing lift vector has moved
aft.
and with stalled main wings the residual main wing lift vector has moved
aft.
even with AoA 60 deg it has moved not to much aft.....
look at the curve of the pitching moment (Cm) against angle of incidence posted by machinbird
http://www.pprune.org/tech-log/39510...ml#post5569978
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Hi Grity,
That was posted well over a year ago, and is mostly a regurgitation of Davies excellent book. That pitching moment curve Davies provided was no doubt derived from a T-tailed aircraft and had a "sticking spot" that kept the aircraft from pitching back down after a deep stall. Probably the more recent pitching moment curves from the FAA generic airliner stall study are more appropriate to AF447.
That was posted well over a year ago, and is mostly a regurgitation of Davies excellent book. That pitching moment curve Davies provided was no doubt derived from a T-tailed aircraft and had a "sticking spot" that kept the aircraft from pitching back down after a deep stall. Probably the more recent pitching moment curves from the FAA generic airliner stall study are more appropriate to AF447.
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>>Have you added in the Earth's velocity vector around the Sun? How about the velocity of the solar system around the Milky Way galaxy?
No, I didn't add this, though I did consider and is the reason I did add the phrase "Due to lack of time, I didn't have the time to think this through for 100%, though I do expect this to be relevant."
And indeed at first glance those aspects do have to be taken into account, though I -think- this is not relevant because the airplane is not acting in the sun's gravitational field. The earth is, but the airplane isn't (because of its low mass).
No, I didn't add this, though I did consider and is the reason I did add the phrase "Due to lack of time, I didn't have the time to think this through for 100%, though I do expect this to be relevant."
And indeed at first glance those aspects do have to be taken into account, though I -think- this is not relevant because the airplane is not acting in the sun's gravitational field. The earth is, but the airplane isn't (because of its low mass).
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>>up to AoA 45 deg the move is very low, even with AoA 60 deg it has moved not to much aft.....
>>look at the curve of the pitching moment (Cm) against angle of incidence posted by machinbird
Yes with a higher AoA it'll become less, though still the same effect.
And on this plane the tail is not in the main wing shadow/wash.
>>look at the curve of the pitching moment (Cm) against angle of incidence posted by machinbird
Yes with a higher AoA it'll become less, though still the same effect.
And on this plane the tail is not in the main wing shadow/wash.
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>>HN39 has done an energy matching simulation (segment by segment) combined with aerodynamic assumptions. (Believe it was in the prior Tech thread.) His conclusion was that the final climb from FL375 to FL 380 was ballistic, i.e. the aircraft started upward on the last dregs of its lift and decelerated below actual level flight stall speed in the climb. This would allow the aircraft to fly below actual level flight stall speed and continue trimming nose up because the AOA had not yet become high enough to shut down the automatic pitch trimming. When gravity caught up with the aircraft and it began to fall, it then went rapidly well past the stall AOA and shut down the automatic pitch trim at 13 degrees ANU.
>>HN39 is very good with this type of thing, and we Physics duffers should respect his knowledge.
>>HN39, if I have gilded the Lilly too badly please correct me.
Yes, I've read that and as explained, those calculations is missing something. As such I started my article. Only for vertical movements, the trade-off in energy can be applied without further side conditions. When changing a horizontal speed into height, other aspects start to act up. If you want more explanation, let me know. I'm aware it's written down pretty condensed.
Maybe I should have mentioned before: I'm not a pilot, though do have a degree in Applied Physics (which includes Control systems behavior at the University I went - some years ago- ).
And: My description also suggests why there are around 10 reported similar upsets. Unexplained upsets without any plausible technical cause. And no, no conspiracies .....
>>HN39 is very good with this type of thing, and we Physics duffers should respect his knowledge.
>>HN39, if I have gilded the Lilly too badly please correct me.
Yes, I've read that and as explained, those calculations is missing something. As such I started my article. Only for vertical movements, the trade-off in energy can be applied without further side conditions. When changing a horizontal speed into height, other aspects start to act up. If you want more explanation, let me know. I'm aware it's written down pretty condensed.
Maybe I should have mentioned before: I'm not a pilot, though do have a degree in Applied Physics (which includes Control systems behavior at the University I went - some years ago- ).
And: My description also suggests why there are around 10 reported similar upsets. Unexplained upsets without any plausible technical cause. And no, no conspiracies .....
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Dutch M..
That sounds very unlikely to me. You are suggesting that the HS is producing lift in the downward (negative) direction despite being at a severe POSITIVE angle of attack.
Imagine your explanation applied to a wing.. You're suggesting that a wing flown at a severe negative angle of attack (so severe that the lower surface is stalled) can still produce positive lift. I'm aware most cambered sections have a zero lift angle of attack that is slightly negative but your suggestion goes way beyond that.
Now to the HS: The intended "lift" for the A330 HS is downward. The speed vector of the AF447 HS on it's path down to earth, is also downward. The pressure gradient is actually pushing the air towards the airfoil. So no reason
at all for boundary separation. More the contrary: Because the downward speed vector "pushes" the airflow on the airfoil, the tendency to boundary separation will be less.
Another aspect relevant in this, is: The HS airfoil does have to curved surfaces,
bottom side a lot, the upper side just little bit. So both sides of the HS generate
lift, where the downward lift force is significantly higher.
Now back to the AF447 HS on it's downward trajectory. The downward speed
is so high that the upper side of the HS airfoil will have (nearly) complete boundary layer separation, so the upper airfoil surface is completely stalled. The net effect is an even greater downward lift vector on the HS.
at all for boundary separation. More the contrary: Because the downward speed vector "pushes" the airflow on the airfoil, the tendency to boundary separation will be less.
Another aspect relevant in this, is: The HS airfoil does have to curved surfaces,
bottom side a lot, the upper side just little bit. So both sides of the HS generate
lift, where the downward lift force is significantly higher.
Now back to the AF447 HS on it's downward trajectory. The downward speed
is so high that the upper side of the HS airfoil will have (nearly) complete boundary layer separation, so the upper airfoil surface is completely stalled. The net effect is an even greater downward lift vector on the HS.
Imagine your explanation applied to a wing.. You're suggesting that a wing flown at a severe negative angle of attack (so severe that the lower surface is stalled) can still produce positive lift. I'm aware most cambered sections have a zero lift angle of attack that is slightly negative but your suggestion goes way beyond that.
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3rd report will be released Friday 29th July...
communiqu 25 juillet 2011
Press release only in French (at the time of writing)... the third report will be published this Friday (29th July), with press conference at 14.30 local time.
"Ce rapport présente les circonstances exactes de l'accident avec des premiers points d'analyse et de nouveaux faits établis à partir de l'exploitation des données des enregistreurs de vol."
The report will present new information established from the flight recorders...
Press release only in French (at the time of writing)... the third report will be published this Friday (29th July), with press conference at 14.30 local time.
"Ce rapport présente les circonstances exactes de l'accident avec des premiers points d'analyse et de nouveaux faits établis à partir de l'exploitation des données des enregistreurs de vol."
The report will present new information established from the flight recorders...
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@Dutch M
I politely suggest you go a read the Wikipedia article on Kinetic Energy. It is correct to use the airmass as reference and airspeed to calculate the KE relative to the axes (its not an absolute quantity). Newton's 2nd law is all about momentum, and momentum is linear in velocity (for constant mass). The equation for Kinetic Energy comes from integrating the momentum from one velocity to another. You do not have to take in account the KE of the system relative to the earth, sun, milkway etc - just use the same axes set before and after. So IMHO it is correct to just use 1/2m(v2^2 - v1^2) = mgh, you do not need intertial equivalents for v. 1/2m(v1-v2)^2 is wrong - unless v1 or v2 are zero!
1. Usage of TAS to calculate Kinetic Energie exchange for height.
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the third report will be published this Friday (29th July), with press conference at 14.30 local time.
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Low/high speed protection availability in ALT2
Hello there
Had the low speed protection been available, would the A/C have been able to zoom climb (or later stall) like it did ?
Had the low speed protection been available, would the A/C have been able to zoom climb (or later stall) like it did ?
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Hi wes wall,
Certainly. And, as it's another interim report, maybe Threads 7, 8 ,9... will follow!
This communiqué means something like this:
This report will present the exact circumstances of the accident, the first analysis pointed, and the new facts established from the flight recorder data's processing.
Originally Posted by wes wall
Better get ready to begin Thread nbr 6. This board is about to get real busy.
This communiqué means something like this:
This report will present the exact circumstances of the accident, the first analysis pointed, and the new facts established from the flight recorder data's processing.
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Hi Hyperveloce,
It's hard to tell as it could be overriden by the pilot, but with VSw displayed, Stall alarms workings... certainly.
Check it by yourself:
*ALTERNATE LAW 2:
- Low speed stability is lost with double ADR fault.
- High speed stability is lost with triple ADR fault.
Originally Posted by Hyperveloce
Had the low speed protection been available, would the A/C have been able to zoom climb (or later stall) like it did ?
Check it by yourself:
*ALTERNATE LAW 2:
- Low speed stability is lost with double ADR fault.
- High speed stability is lost with triple ADR fault.
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Going round in circles
Originally Posted by Dutch M
I'm not a pilot, though do have a degree in Applied Physics
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Hi Hyperveloce,
It's hard to tell as it could be overriden by the pilot, but with VSw displayed, Stall alarms workings... certainly.
Check it by yourself:
*ALTERNATE LAW 2:
- Low speed stability is lost with double ADR fault.
- High speed stability is lost with triple ADR fault.
It's hard to tell as it could be overriden by the pilot, but with VSw displayed, Stall alarms workings... certainly.
Check it by yourself:
*ALTERNATE LAW 2:
- Low speed stability is lost with double ADR fault.
- High speed stability is lost with triple ADR fault.
Hi Takata. Ok, the gentle ND introduced by the low speed prot. can be overriden by the PF (and maybe the PF persistant NU inputs were to counteract the low speed prot. ND orders, but he did so much more than that). But if we consider the past UAS incidents analyzed by the BEA, do we see a single occurrence of a low/high speed prot. activation when the ALT2 was triggered by a NAV disagreement ? In a few past cases, a descent (never more than 5000 ft) was decided when the stall warnings sounded but it was a PF action. Can we assume that these low and high prot. were not available in all these UAS incidents and in the AF 447 case ?