AF 447 Thread No. 9
DozyWannabe, #901
I brought my two lads up to question everything, especially the
things they trust the most :-). You seem to be basing absolute
trust in the BEA, when of course, everything they say has political
/ legal implications and will be phrased in a particular way. I'm
not saying that anything they say in the report is innaccurate, or
that they haven't done a thorough job, but they above all should be
subject to the the most rigorous scrutiny. Not only for what they
say but in particular, what they don't.
With respect, to be truly impartial, you need to question a lot more,
rather than appearing as an apologist at every turn :-)...
You clearly don't know me well - it's not about having "faith in [any]
Institution", but a desire for factual accuracy and an intense distaste
for politically-motivated conspiracy theories.
The BEA's only job is to establish the relevant facts - you can bet
that one of the ambulance-chasers will try to make hay out of the
autotrim feature. After all, the biggest source of misinformation
as it applies to aviation accidents tends to come from lawyers
releasing scuttlebutt to the press.
Institution", but a desire for factual accuracy and an intense distaste
for politically-motivated conspiracy theories.
The BEA's only job is to establish the relevant facts - you can bet
that one of the ambulance-chasers will try to make hay out of the
autotrim feature. After all, the biggest source of misinformation
as it applies to aviation accidents tends to come from lawyers
releasing scuttlebutt to the press.
things they trust the most :-). You seem to be basing absolute
trust in the BEA, when of course, everything they say has political
/ legal implications and will be phrased in a particular way. I'm
not saying that anything they say in the report is innaccurate, or
that they haven't done a thorough job, but they above all should be
subject to the the most rigorous scrutiny. Not only for what they
say but in particular, what they don't.
With respect, to be truly impartial, you need to question a lot more,
rather than appearing as an apologist at every turn :-)...
Originally Posted by DozyWannabe
Confiture
DozyWannabe
DozyWannabe, why do you still reference your statements to outside sources like your TRE from the sim, when it is all written in the BEA final report?
BEA Final report 1.16.3.2 Analysis of the operation of the stall warning
The first warning was not. This is not coming from me, this is coming from the TRE on the sim day, who was well-versed in the event.
The first warning was real and should have been longer, dixit the BEA.
Are we talking about the same warning? I'm talking about the single "blip" on the traces at about 02:10:08 - that was a single "G"-induced warning, and the aircraft was not about to stall at that point. The first non-transient warning (where the aircraft was actually approaching stall) began at approx. 02:10:48 according to the traces.
BEA Final report 1.16.3.2 Analysis of the operation of the stall warning
The activations of the warning picked up by the CVR were identified as occurring at between 2 h 10 min 10.4 and 11.3 and between 2 h 10 min 13 and 13.4. The short duration of activation did not make it possible to detect it from the “Stall warning” parameter, but the FWC 1’s “Master warning” parameters were triggered on one point at this time. However, this warning should have continued until about 2 h 10 min 15.5, and then have been triggered again between 2 h 10 min 17 and 19. The disabling of this warning was probably due to the fact that, between 13.4 and 15.5 and then between 17 and 19, and possibly at other times, the three Mach values were abnormally low (three Pitot probes iced up). The warning triggering threshold then suddenly increased to values of about 10°, much greater than the recorded angles of attack, which led to the warning stopping.
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when of course, everything they say has political / legal implications and will be phrased in a particular way
It is through this alliance that most of the rumour surrounding these cases seems to have been established, and on thorough investigation, few if any of these rumours turn out to be credible - however they've done their work, as the rumours tend to be propagated years or even decades later
Not only for what they say but in particular, what they don't.
With respect, to be truly impartial, you need to question a lot more, rather than appearing as an apologist at every turn :-)...
The fact is that the motivation behind a lot of the "questions" on here is based on incorrect information relating to the BEA, and a quixotic desire to hurt Airbus because of a misunderstanding of the motivation behind the introduction of FBW - as well as an incident more than two decades ago that didn't go their way.
[EDIT : In addition, those clamouring for the BEA to release information on aspects of the investigation that led to potential causes being ruled out seem to forget that this information is not released within the reports themselves, but tends to come in the years following, from interviews conducted with the investigators for books like MacArthur Job's - or for TV/film purposes. I noted a while back that the Mayday/ACI series on NatGeo has blocked it's final show of the 2012 season to be on AF447 - could be interesting, even if it's a high-level overview. ]
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Stall warning not real?
Originally Posted by DozyWannabe
And the evidence indicates that the actual AoA of the aircraft was not consistent with stall at that point.
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HN39 - that's sort-of what I was saying. The threshold was exceeded in a transient sense (due to "G" loading and possibly turbulence), but the aircraft was not in danger of actually approaching stall until the apex of the climb.
The point I was trying to make was that while the warning was caused by exceeding the threshold, the aircraft was not in danger of stalling at that point - I was trying to head off another flight of fancy.
The point I was trying to make was that while the warning was caused by exceeding the threshold, the aircraft was not in danger of stalling at that point - I was trying to head off another flight of fancy.
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the aircraft was not in danger of actually approaching stall until the apex of the climb
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Which is why (quite correctly) the warning does not differentiate between transient and non-transient. However because we have the full DFDR traces we can say with a measure of certainty at which points during the incident timeline the aircraft was approaching stall and stalled and when it was not.
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the idea that the BEA are somehow politically motivated to protect Airbus.
The BEA is certainly not politically motivated to protect anyone
By cons .. number of politicians (or government) are often highly motivated to protect the interests of the country (economy .. defense .. prestige .. etc)
It should probably not be recalled here that the BEA is a body under the french Ministry of Transport (sous tutelle)
In fact .. Mr Troadec (chief of staff BEA) and all are civil servants
If one day he (Troadec) would disagree with the Ministry of Transport .. the only way he could know would be to resign
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@jcj:
But civil servants are not politicians - by and large they just do the job that they have been asked to do. Accident investigation has always been something of a unique case in that regard, because the purpose must always be to find what went wrong and prevent it from happening again.
The one time in living memory when it was proven that an aviation authority colluded with politicians and a manufacturer to soft-pedal design problems (overriding the accident investigators in the process), it ended up blowing up in their faces, and condemning the airliner involved (the DC-10) to a chequered reputation in perpetuity. To do so is clearly not worth the risk.
But civil servants are not politicians - by and large they just do the job that they have been asked to do. Accident investigation has always been something of a unique case in that regard, because the purpose must always be to find what went wrong and prevent it from happening again.
The one time in living memory when it was proven that an aviation authority colluded with politicians and a manufacturer to soft-pedal design problems (overriding the accident investigators in the process), it ended up blowing up in their faces, and condemning the airliner involved (the DC-10) to a chequered reputation in perpetuity. To do so is clearly not worth the risk.
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Hi,
DW
This is ignoring the fact that politicians can take risks at any price with no fear
Courtesy .. with the help of the press ... see under ..
For the frenchs .. just remind the Rainbow Warrior case
They made it before .. why no make it after ... ( this is actually some cases pending ... )
DW
The one time in living memory when it was proven that an aviation authority colluded with politicians and a manufacturer to soft-pedal design problems (overriding the accident investigators in the process), it ended up blowing up in their faces, and condemning the airliner involved (the DC-10) to a chequered reputation in perpetuity. To do so is clearly not worth the risk.
aided and abetted by a press who have an insatiable appetite for a juicy scandal.
For the frenchs .. just remind the Rainbow Warrior case
They made it before .. why no make it after ... ( this is actually some cases pending ... )
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(And you're talking about a military operation, which is a far cry from accident investigation)
I'm reminded of an anecdote I once read that took place during the Comet investigation - no less a politician than then-PM Winston Churchill (who I have no special regard for, but respect his tenacity) asked for the ambassador to Italy, only to be told he was off 'showing the flag'. Churchill's response was along the lines of "Tell him to get back at once and sort out this Comet problem, or there won't be a flag to wave!".
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HazelNuts39
Was there any evidence of preStall buffet with the first SWs? I am wondering if it is at all possible that PNF had felt or heard buffet consonant with the warning? I am willing to agree his comment was related to the SW only, but is it eliminated in the traces it could be something else? I think the BEA have left this open?
Thanks HN
Was there any evidence of preStall buffet with the first SWs? I am wondering if it is at all possible that PNF had felt or heard buffet consonant with the warning? I am willing to agree his comment was related to the SW only, but is it eliminated in the traces it could be something else? I think the BEA have left this open?
Thanks HN
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Which is why (quite correctly) the warning does not differentiate between transient and non-transient. However because we have the full DFDR traces we can say with a measure of certainty at which points during the incident timeline the aircraft was approaching stall and stalled and when it was not.
Do the pilots had the full DFDR unfolding under their eyes ... ?
And if he had been .. do they have had time to analyze it?
How pilots could have known the difference ?
This shows the gap that exists between an analysis of the actions (pilots and plane) ... and actions in real time
Reconciling the two is difficult
PS
BTW it's unfortunate that the full DFDR (listing) is not annexed to the BEA report
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@jcj:
It doesn't matter in this case, because even if the transient warnings were acknowledged as a sign of imminent stall, to pull the nose up to 15 degrees and hold it there is not and never has been the correct response.
It doesn't matter in this case, because even if the transient warnings were acknowledged as a sign of imminent stall, to pull the nose up to 15 degrees and hold it there is not and never has been the correct response.
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Originally Posted by Lyman
Was there any evidence of preStall buffet with the first SWs?
DozyWannabe
HN39 - that's sort-of what I was saying. The threshold was exceeded in a transient sense (due to "G" loading and possibly turbulence), but the aircraft was not in danger of actually approaching stall until the apex of the climb.
The point I was trying to make was that while the warning was caused by exceeding the threshold, the aircraft was not in danger of stalling at that point - I was trying to head off another flight of fancy.
HN39 - that's sort-of what I was saying. The threshold was exceeded in a transient sense (due to "G" loading and possibly turbulence), but the aircraft was not in danger of actually approaching stall until the apex of the climb.
The point I was trying to make was that while the warning was caused by exceeding the threshold, the aircraft was not in danger of stalling at that point - I was trying to head off another flight of fancy.
BEA Final report 1.16.3.2 Analysis of the operation of the stall warning
The activations of the warning picked up by the CVR were identified as occurring at between 2 h 10 min 10.4 and 11.3 and between 2 h 10 min 13 and 13.4. The short duration of activation did not make it possible to detect it from the “Stall warning” parameter, but the FWC 1’s “Master warning” parameters were triggered on one point at this time. However, this warning should have continued until about 2 h 10 min 15.5, and then have been triggered again between 2 h 10 min 17 and 19. The disabling of this warning was probably due to the fact that, between 13.4 and 15.5 and then between 17 and 19, and possibly at other times, the three Mach values were abnormally low (three Pitot probes iced up). The warning triggering threshold then suddenly increased to values of about 10°, much greater than the recorded angles of attack, which led to the warning stopping.
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@franzl
We're talking at cross-purposes here. The BEA say they should have sounded for longer based on the data they have - I'm not disagreeing with that. The nature of that warning seems to be that it would have stopped during the brief period the nose starts to come down after the initial 15 degree pitch-up. Had 15 degrees been held it would have definitely approached actual stall earlier. However. after bringing it back down for a few seconds the PF pulled the nose up again - to just shy of 20 degrees this time, and the stall warning sounded continuously until the indicated speed bled off to the AoA vane cutoff point (i.e. <60kts).
Note that the BEA are referring to transient bursts of the stall warning which do not correlate with the DFDR graphs. The transient warning I was referring to does indeed appear on the graph.
We're talking at cross-purposes here. The BEA say they should have sounded for longer based on the data they have - I'm not disagreeing with that. The nature of that warning seems to be that it would have stopped during the brief period the nose starts to come down after the initial 15 degree pitch-up. Had 15 degrees been held it would have definitely approached actual stall earlier. However. after bringing it back down for a few seconds the PF pulled the nose up again - to just shy of 20 degrees this time, and the stall warning sounded continuously until the indicated speed bled off to the AoA vane cutoff point (i.e. <60kts).
Note that the BEA are referring to transient bursts of the stall warning which do not correlate with the DFDR graphs. The transient warning I was referring to does indeed appear on the graph.
Last edited by DozyWannabe; 31st Jul 2012 at 15:38.
@DW
I do not agree, please recheck.
BEA is talking about the identical two warnings in the same timeframe. It adresses the logic of the stall warning, and that it should have sounded longer than it did and three times instead of two times. And it didn´t sound that long, because the threshold, at which the stall warning is activated, increased to about 10° AOA (which is not depicted in the FDR- trace with the green line) due to the abnormal (not actual) Mach number. The threshold is lower at high mach, higher at lower mach. As mach was wrong due to the iced pitots, the warning threshold was set too high and therefore the warning sounded too short.
If you compare the mentioned times from BEA with the figure 62 of Final report, you will see that the warning sounded shorter than depicted looking like spurious and thus not understood by the crew. And that is exactly what BEA states under 1.16.3.2 Analysis of the operation of the stall warning.
Why the wrong movement of the threshold like mentioned by BEA is not depicted in Figure 62 FDR traces with the green line, i dont know. But the faulty mach is depicted above. Maybe this line has a different origin and is not mach dependent.
The warning was valid, however it was not presented to the crew in the apropriate long time frame due to the iced pitots.
I do not agree, please recheck.
BEA is talking about the identical two warnings in the same timeframe. It adresses the logic of the stall warning, and that it should have sounded longer than it did and three times instead of two times. And it didn´t sound that long, because the threshold, at which the stall warning is activated, increased to about 10° AOA (which is not depicted in the FDR- trace with the green line) due to the abnormal (not actual) Mach number. The threshold is lower at high mach, higher at lower mach. As mach was wrong due to the iced pitots, the warning threshold was set too high and therefore the warning sounded too short.
If you compare the mentioned times from BEA with the figure 62 of Final report, you will see that the warning sounded shorter than depicted looking like spurious and thus not understood by the crew. And that is exactly what BEA states under 1.16.3.2 Analysis of the operation of the stall warning.
Why the wrong movement of the threshold like mentioned by BEA is not depicted in Figure 62 FDR traces with the green line, i dont know. But the faulty mach is depicted above. Maybe this line has a different origin and is not mach dependent.
The warning was valid, however it was not presented to the crew in the apropriate long time frame due to the iced pitots.
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Nevertheless it does not alter the fact that it appears the crew did not respond in the correct manner to either the transient or sustained stall warnings, instead keeping the nose up.
Last edited by DozyWannabe; 31st Jul 2012 at 16:41.
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