TAM A320 crash at Congonhas, Brazil
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Originally Posted by donstim
I realize that English may not be your native language, but when "because" is used the way you used it (with a single cause and effect), it does indeed imply "only."
I am sorry you didn't understand what I meant, but now that you do, could we possibly drop the subject?
[I just tried to send you a private message with the reason why your claim that use of "because" implies enumerating all causes is false. But you don't receive private messages. What a shame. I'm not going to belabor the thread with it.]
PBL
Last edited by PBL; 7th Sep 2007 at 16:56.
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(By the way: Yes, it would)
Why are you continually trying to push the 'Innocent pilots let down by faulty aircraft' angle? What do you have to gain?
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Yes after the autothrust disconnect, at 18:48:29, cf. p. 3, FDR graphs). In case of an "involuntary disconnect" of autothrust, i. e. any mode of disconnect other than bringing both levers to idle or pressing the pushbutton on the lever side, thrust remains locked. Until the levers are moved.
First let me just make a summary:
No controversy about A/THR behaviour. It worked as expected in any case in which one of the TLA readings remained in climb.
The right engine thrust never surpassed climb power as expected. It remained locked at ca. 1.18 EPR. after A/THR desengaged therefore below CLB power.
From here we have four possibilities:
1 - The right TL wasn´t physically brought to idle and remained "untouched" until the very end;
2 - The right TL was brought to idle but the TLA reading remained at CLB. The right TL remained "untouched" ever since. The crew didn't figure out right engine EPR was above idle;
3 - The right TL was brought to idle but the TLA reading remained at CLB. The crew tried to put the right engine thrust back to idle moving the right TL but the thrust remained locked;
4 - The right TL was physically locked, meaning that the FP couldn't phisically move it even when he tried to do so.
Last edited by flyingnewbie10; 7th Sep 2007 at 16:46. Reason: typo
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Why are you continually trying to push the 'Innocent pilots let down by faulty aircraft' angle? What do you have to gain?
Now back to you...Why do you resist that much to consider other explanations for the accident ?
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...because he's thinking logically and you are not!
Let me review some facts:
1 - The crew followed the right procedure in the previous landing (maybe they changed seats in Congonhas what could explain the FP "forgetting" the TL at climb);
2 - There is an (apparently) anomalous right TLA reading at idle stop in the previous landing in Porto Alegre;
3 - An Audio Spectrum Analysis could show whether both or a single TL was pulled to idle;
4 - There isn't a sufficiently detailed explanation of the A320's TCU mechanism and its software interface to rule out a mechanical/electronical failure yet.
Do yout think it is logical in a context of an accident investigation to rule out the possibilitly of a mechanical/electronical failure from the beginning ?
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Originally Posted by flyingnewbie10
First let me just make a summary:
[...]
[...]
Here's the article in our compendium, here's the actual PDF file of the analysis.
I recommend PBL's introductory article, as it contains a lot or explanatory remarks on the Why-Because Graph. To those unfamiliar with the Why-Because-Analysis I also highly recommend the the Why-Because-Analysis web pages.
Your comments will be appreciated.
Bernd
Last edited by bsieker; 7th Sep 2007 at 17:11. Reason: Added URL to PDF file.
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Here's the article in our compendium, and here is an introduction to the analysis technique we use, called the Why-Because-Analysis.
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Come on, guys! Let's at least give newbie credit for knowing something about law and courts; it is his profession.
All kinds of analysis, including analysing the sounds on a recording and what they might meant, are admissible in evidence. Usually, it requires the analyst turning up in court and verifying that the piece of evidence is, indeed, hisher analysis and explaining hisher conclusions. And it requires that the piece of evidence (the analysis) satisfy the rules of evidence, which suffice to ensure for example that the presented analysis is indeed of the CVR of the actual accident being discussed and not of some other accident, or a simulation, and so on.
Whether the court believes anything of what is said is, of course, entirely another matter.
Newbie wants to leave open the possibility that the signal recorded on the FDR and interpreted by the FADECs may have had some other cause than that the thrust lever was left voluntarily near the CL detent. That is his privilege. Let us please recognise that, at this stage, nobody has the evidence to contradict him.
PBL
All kinds of analysis, including analysing the sounds on a recording and what they might meant, are admissible in evidence. Usually, it requires the analyst turning up in court and verifying that the piece of evidence is, indeed, hisher analysis and explaining hisher conclusions. And it requires that the piece of evidence (the analysis) satisfy the rules of evidence, which suffice to ensure for example that the presented analysis is indeed of the CVR of the actual accident being discussed and not of some other accident, or a simulation, and so on.
Whether the court believes anything of what is said is, of course, entirely another matter.
Newbie wants to leave open the possibility that the signal recorded on the FDR and interpreted by the FADECs may have had some other cause than that the thrust lever was left voluntarily near the CL detent. That is his privilege. Let us please recognise that, at this stage, nobody has the evidence to contradict him.
PBL
Per Ardua ad Astraeus
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By no means my first go at this question and so far only one 'interested party'.
I am puzzled by the low (recorded) EPR on the number 1 engine in reverse in the final landing at CGH. If I were landing on a limiting (and possibly) slippery runway with 1 (or 2 reversers) I would be using full reverse until my stop was assured. This to me would give me a clue to the (sadly) missing mindset/briefing for the landing.
I wonder if some kind EPR driven 320 pilot could (at a suitably calm moment, of course
) note the EPR for idle reverse and another time for full reverse? Please either post here or PM me with the results if you would be so kind.
I am puzzled by the low (recorded) EPR on the number 1 engine in reverse in the final landing at CGH. If I were landing on a limiting (and possibly) slippery runway with 1 (or 2 reversers) I would be using full reverse until my stop was assured. This to me would give me a clue to the (sadly) missing mindset/briefing for the landing.
I wonder if some kind EPR driven 320 pilot could (at a suitably calm moment, of course
) note the EPR for idle reverse and another time for full reverse? Please either post here or PM me with the results if you would be so kind.
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PBL:
Newbie wants to leave open the possibility that the signal recorded on the FDR and interpreted by the FADECs may have had some other cause than that the thrust lever was left voluntarily near the CL detent. That is his privilege. Let us please recognise that, at this stage, nobody has the evidence to contradict him.
Newbie wants to leave open the possibility that the signal recorded on the FDR and interpreted by the FADECs may have had some other cause than that the thrust lever was left voluntarily near the CL detent. That is his privilege. Let us please recognise that, at this stage, nobody has the evidence to contradict him.
Flyingnewbie10, I apologise if I've come across as combative - I just want to make sure that we're not going back over old ground.
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Reverse EPR
To BOAC,
EPR at full reverse seems to be approximately 1.05.
Number seems not very high, but EPR measurement is apparently not very realistic in the disturbed flow situation during reverse application.
EPR at idle, either forward or reverse would be about 1.00
The 1.05 I have gathered from QAR data readouts of a couple of my own landings.
A better indication of engine output during reverse would be N1, but to tell you the truth, I have never checked those numbers. I just hear the noise and feel the deceleration, and look out in front to judge whether deceleration satisfies me.
The thrust lever angle for full reverse is (-)22.5 degrees, perhaps you can deduce that number from the FDR readout.
EMIT.
(added line about full reverse TLA).
EPR at full reverse seems to be approximately 1.05.
Number seems not very high, but EPR measurement is apparently not very realistic in the disturbed flow situation during reverse application.
EPR at idle, either forward or reverse would be about 1.00
The 1.05 I have gathered from QAR data readouts of a couple of my own landings.
A better indication of engine output during reverse would be N1, but to tell you the truth, I have never checked those numbers. I just hear the noise and feel the deceleration, and look out in front to judge whether deceleration satisfies me.
The thrust lever angle for full reverse is (-)22.5 degrees, perhaps you can deduce that number from the FDR readout.
EMIT.
(added line about full reverse TLA).
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Evidence...Logic...Facts...Truth
FlyingNewbie10, PBL,
I agree, but some might interpret PBL's latest as damning FN with faint praise.
Let me try to say this again in the hope of getting through to some who seem uncomfortable with contemplating any possible explanation except blaming the pilots, without recourse to any logical process, mentioning no names (Dani).
From the FDR evidence in the public domain one can infer only the following concerning the TLs:
"The FDR recorded a valid commanded No.2 TLA of CLB throughout the landing roll."
My best guess is that the FDR TLA commanded signal comes from the EEC in command of the subject engine. Dual FADEC has 2 EECs (engine electronic control) per engine.
Two (a subset of all) possible reasons for this occurring are:
(1) The pilots left No.2 TL at CLB
(2) No.2 TL was brought to idle but the thrust control unit (TCU) continued to provide a valid TLA commanded = CLB signal.
From anecdotes on this thread, reason (1) appears to have contributed to several previous incidents. It is possible (some are of the opinion that it is overwhelmingly likely) that this happened in this case.
It is not acceptable to state that (2) did not happen at Congonhas unless you have the evidence to prove it. There are several failure modes that could produce this effect (see my post 1981).
I agree, but some might interpret PBL's latest as damning FN with faint praise.
Let me try to say this again in the hope of getting through to some who seem uncomfortable with contemplating any possible explanation except blaming the pilots, without recourse to any logical process, mentioning no names (Dani).
From the FDR evidence in the public domain one can infer only the following concerning the TLs:
"The FDR recorded a valid commanded No.2 TLA of CLB throughout the landing roll."
My best guess is that the FDR TLA commanded signal comes from the EEC in command of the subject engine. Dual FADEC has 2 EECs (engine electronic control) per engine.
Two (a subset of all) possible reasons for this occurring are:
(1) The pilots left No.2 TL at CLB
(2) No.2 TL was brought to idle but the thrust control unit (TCU) continued to provide a valid TLA commanded = CLB signal.
From anecdotes on this thread, reason (1) appears to have contributed to several previous incidents. It is possible (some are of the opinion that it is overwhelmingly likely) that this happened in this case.
It is not acceptable to state that (2) did not happen at Congonhas unless you have the evidence to prove it. There are several failure modes that could produce this effect (see my post 1981).
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Facts, etcetera.
To SYENG,
Good post about what can be taken as fact and what is deduction.
Having said that, I trust the investigators enough to leave the microscopic testing of wreckage parts to them, and to trust their impartiality in the final report.
Next point is, as a pilot, I think that the most valuable point to ponder is, the question how or why did the PF leave the T/L #2 in CLB detent?
EMIT.
Good post about what can be taken as fact and what is deduction.
Having said that, I trust the investigators enough to leave the microscopic testing of wreckage parts to them, and to trust their impartiality in the final report.
Next point is, as a pilot, I think that the most valuable point to ponder is, the question how or why did the PF leave the T/L #2 in CLB detent?
EMIT.
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Originally Posted by flyingnewbie10
It leaves approach thrust and surpasses climb EPR (apparently).
There is no such thing as "approach thrust" as a fixed value, which can be "left".
Unlike "maximum climb thrust" ("CLIMB", the highest thrust used after thrust reduction on a normal flight), "maximum continuous thrust" ("MCT", the highest thrust used during single-engine operation after thrust reduction) and "maximum take-off-thrust ("TOGA"), which are more or less constant.
Approach thrust is whatever is necessary to maintain approach speed.
Obviously, with both engines operating that is a lot less than if a single engine has to achieve that, so consequently EPR rises.
As you can see, during the approach, the EPR value fluctuated between 1.1 and 1.06.
Bernd
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EMIT,
As I've said before, my feeling (and that's not worth anything, really) is that it is more likely (but not overwhelmingly) that the TL was left in the climb detent than there was a mechanical disconnection between the TLs and the TCU.
It is humbling to witness the infallibility which pilots seem to attribute to those who design and those who maintain the systems of mechanical, electrical and electronic linkages which you never see, but rely on for the lives of yourselves and your trusting passengers.
The formal enquiry needs to rule out a linkage failure (based on evidence) if it is to safely conclude that the TL was left at CLB. Even if it doesn't, Airbus would be as well to re-visit the ATA76 FMEA.
I've had enough of re-iterating the same old points and I concede that I'll never get through to those who have already made their minds up, so I'll shut up now.
As I've said before, my feeling (and that's not worth anything, really) is that it is more likely (but not overwhelmingly) that the TL was left in the climb detent than there was a mechanical disconnection between the TLs and the TCU.
It is humbling to witness the infallibility which pilots seem to attribute to those who design and those who maintain the systems of mechanical, electrical and electronic linkages which you never see, but rely on for the lives of yourselves and your trusting passengers.
The formal enquiry needs to rule out a linkage failure (based on evidence) if it is to safely conclude that the TL was left at CLB. Even if it doesn't, Airbus would be as well to re-visit the ATA76 FMEA.
I've had enough of re-iterating the same old points and I concede that I'll never get through to those who have already made their minds up, so I'll shut up now.
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Bsieker,
I will dare to post a preliminary comment about your why-because graph. My apologies If I say any nonsense:
1 - Factor 11 (assumption) could well be the one you pointed out (F/C did not expect autobrake not to operate) to explain F/C not commencing "Loss of Braking" procedure immediatelly. But if "Loss of Braking" implies using full manual braking (is it ?) I suppose it could also be explained by the fact that the crew at least thought that the runway was slippery and did not start using braking immediatelly to avoid an hydroplanning as the speed was still high;
2 - Is there a way to have a more detailed description of factor 18 (Thrust Lock after A/THR disconnected) just to contemplate the fact that it worked exactly as designed and the "locked" thrust was within the range of the right TLA reading ?;
3 - Does the graph accept multiple assumptions ? Could Factors 36 and 42 have parallel hypothesis ?
I will dare to post a preliminary comment about your why-because graph. My apologies If I say any nonsense:
1 - Factor 11 (assumption) could well be the one you pointed out (F/C did not expect autobrake not to operate) to explain F/C not commencing "Loss of Braking" procedure immediatelly. But if "Loss of Braking" implies using full manual braking (is it ?) I suppose it could also be explained by the fact that the crew at least thought that the runway was slippery and did not start using braking immediatelly to avoid an hydroplanning as the speed was still high;
2 - Is there a way to have a more detailed description of factor 18 (Thrust Lock after A/THR disconnected) just to contemplate the fact that it worked exactly as designed and the "locked" thrust was within the range of the right TLA reading ?;
3 - Does the graph accept multiple assumptions ? Could Factors 36 and 42 have parallel hypothesis ?
Last edited by flyingnewbie10; 7th Sep 2007 at 21:58. Reason: considering only speed as a factor in acquaplanning
Mistrust in Management
flyingnewbie10
I suppose it could also be explained by the fact that the crew at least thought that the runway was slippery and did not start using full braking power immediatelly to avoid an hydroplanning
Hydroplaning (or aquaplaning) will occur regardless of brake application - it is a function of tyre pressure, speed and depth of water. The relevant point is that if the criteria for aquaplaning are present then the application of brakes will be very ineffective; the application of braking does not in itself cause aquaplaning.
Regards
Exeng
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I've had enough of re-iterating the same old points and I concede that I'll never get through to those who have already made their minds up, so I'll shut up now.
Please remember that not everybody here has made his mind up
This is just a guess (probably flawed)
I saw the picture you posted about the TL mechanism and I tried to figure out how a "broken" or "loose" link between the pushrods, artificial feel unit and TLA sensor box could eventually yield that wrong TLA reading at the right TL idle stop.
Maybe the artificial feel unit and the TLA sensor box pushrod link was somehow loose (The last pushrod from top to bottom being "below" his correct position) thus marking a "negative" TLA reading.
But this would not explain the correct TLA reading for the other TL positions (CLIMB, etc).
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Trust in engineers
SYENG,
Although I have trust in engineers, I know that things can and will break or go wrong. Just 2 weeks ago I had a case of a blocked pitot tube, but because we (my copilot and I) played the game the way it should be played, we didn't make any headlines like e.g. Birgenair in POP.
I think it is not a case of being levelheaded if the pilots on this forum are more inclined to view this affair from the human factors side, which is their daily bread and butter, while leaving the detailed analysis of the wreckage to the technical experts.
good night now.
Although I have trust in engineers, I know that things can and will break or go wrong. Just 2 weeks ago I had a case of a blocked pitot tube, but because we (my copilot and I) played the game the way it should be played, we didn't make any headlines like e.g. Birgenair in POP.
I think it is not a case of being levelheaded if the pilots on this forum are more inclined to view this affair from the human factors side, which is their daily bread and butter, while leaving the detailed analysis of the wreckage to the technical experts.
good night now.