TAM A320 crash at Congonhas, Brazil
Join Date: Jul 2007
Location: BRU
Posts: 82
Likes: 0
Received 0 Likes
on
0 Posts
PBL wrote
No, I don t in any case, but it is clear that during the three last landings TL were handled inconsistently. (The 3054 crew flew the to last legs - the junior TAM pilot was PF at Porto Alegre and apparently performed according to latest Airbus instructions)
Do we know that that was not TAM 1-TR-INOP SOP at the time?
No, I don t in any case, but it is clear that during the three last landings TL were handled inconsistently. (The 3054 crew flew the to last legs - the junior TAM pilot was PF at Porto Alegre and apparently performed according to latest Airbus instructions)
Join Date: Jan 2001
Location: UK
Posts: 2,044
Likes: 0
Received 0 Likes
on
0 Posts
What is also disturbing (or the FDR is not telling the truth due to some underlying problem in the TLAs?) to see is that in their 2nd previous landing they only set the TL2 to IDLE (while reversing TL1 as should). But in the previous landing (ie just before the accident) they reversed both TLs as one would with both TRs operating?
If you find that disturbing, you must be perfect
I think you will find most A320 series pilots forgot this quite a lot of the time... 
As to why they did it 3 different 3 ways in 3 different landings, I could make a set of guesses. However, lets leave that to the pros, and the trick cyclists they may bring in to analyse human behaviour... which I still contend is the likely basis of this accident.
PPRuNe supporter
Join Date: Dec 2003
Location: Planet Earth
Posts: 1,677
Likes: 0
Received 0 Likes
on
0 Posts
If you find that disturbing, you must be perfect I think you will find most A320 series pilots forgot this quite a lot of the time...
Not trying to be an investigator, just enjoying the discussion as seen from the different points of view.
D.L.
Join Date: Jul 2007
Location: Germany
Posts: 556
Likes: 0
Received 0 Likes
on
0 Posts
Rough stopping distance estimate from FDR graphs
This is a very rough estimate, based on the deceleration shown in the FDR graphs.
If I read that right, the achieved deceleration at full manual brake application was around 1.5m/s^2.
When noticing "no spoilers" they were still going at around 140kt, which is about 72m/s.
The stopping distance (SD) for a known (assumed constant) deceleration (a) and known initial speed (v0) is:
SD = v0^2 / 2a, thus
SD = (72 m/s)^2 / (2*1.5m/s^2)
= 1728m.
In practice probably a bit shorter, since with less lift, WoW and thus normal force, and thus deceleration will become higher.
Still, this looks worse than earlier estimates.
It is interesting to note that, contrary to what I said above, deceleration at the onset of manual braking reached about 2m/s^2 for a few seconds, and then decreased to between 1 and 1.5.
(1g is 9.81m/s^2, so 0.1g is roughly 1m/s^2, precise enough for this estimate)
Bernd
If I read that right, the achieved deceleration at full manual brake application was around 1.5m/s^2.
When noticing "no spoilers" they were still going at around 140kt, which is about 72m/s.
The stopping distance (SD) for a known (assumed constant) deceleration (a) and known initial speed (v0) is:
SD = v0^2 / 2a, thus
SD = (72 m/s)^2 / (2*1.5m/s^2)
= 1728m.
In practice probably a bit shorter, since with less lift, WoW and thus normal force, and thus deceleration will become higher.
Still, this looks worse than earlier estimates.
It is interesting to note that, contrary to what I said above, deceleration at the onset of manual braking reached about 2m/s^2 for a few seconds, and then decreased to between 1 and 1.5.
(1g is 9.81m/s^2, so 0.1g is roughly 1m/s^2, precise enough for this estimate)
Bernd
Last edited by bsieker; 10th Aug 2007 at 10:58. Reason: minor correction in the units.
Join Date: Sep 2000
Location: Bielefeld, Germany
Posts: 955
Likes: 0
Received 0 Likes
on
0 Posts
Danny suggested
Doesn't show in the braking figures. They went from 130 kts at 18:48:36, when brakes were first registered full, to 95 kts by 18:48:50, end of data.
That is 66 m/s to 48.3 m/s in 14 seconds.
So 48.3 = a.14 + 66, giving a = -1.26 m/s/s which is, if I remember rightly, better than the target deceleration with Autobrake MED.
PBL
Originally Posted by Danny
there is a very strong chance that the a/c was aquaplaning when brakes were applied.
That is 66 m/s to 48.3 m/s in 14 seconds.
So 48.3 = a.14 + 66, giving a = -1.26 m/s/s which is, if I remember rightly, better than the target deceleration with Autobrake MED.
PBL
Join Date: Jul 2007
Location: Germany
Posts: 556
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by PBL
So 48.3 = a.14 + 66, giving a = -1.26 m/s/s which is, if I remember rightly, better than the target deceleration with Autobrake MED.
LO is 1.7 m/s^2
MED is 3.0 m/s^2
Still, 1.26 m/s^2 is a lot better than aquaplaning.
Bernd
PPRuNe supporter
Join Date: Dec 2003
Location: Planet Earth
Posts: 1,677
Likes: 0
Received 0 Likes
on
0 Posts
Well it's amazing how all the experts here seem to be indicating to us that deceleration was fine, and the runway was adequate in lieu of the fact that spoilers were not deployed, maybe they could please shed some light on the fact that, if braking was so effective, why did the aircraft leave the airport at approximately 94 KTS? 
Join Date: Dec 2001
Location: Finland
Age: 44
Posts: 121
Likes: 0
Received 0 Likes
on
0 Posts
hetfield,
No, probably not. But now that it has been published, it allows us to view the "picture" of what happened more clearly. Albeit with absolutely no information on other critical aspects, or more detailed information on what was going on inside the aircraft systems at that time. So basically all the speculation here is "useless", and just speculation. Without knowing all of the details available to the investigators.
Still, I don't quite see the problem of discussion either. This is a topic that might teach somebody something in the end. Maybe something so useful that it will prevent an incident or accident in some future circumstances. There's nothing here to require secrecy, I think.
Tero
No, probably not. But now that it has been published, it allows us to view the "picture" of what happened more clearly. Albeit with absolutely no information on other critical aspects, or more detailed information on what was going on inside the aircraft systems at that time. So basically all the speculation here is "useless", and just speculation. Without knowing all of the details available to the investigators.
Still, I don't quite see the problem of discussion either. This is a topic that might teach somebody something in the end. Maybe something so useful that it will prevent an incident or accident in some future circumstances. There's nothing here to require secrecy, I think.
Tero
Per Ardua ad Astraeus
Join Date: Mar 2000
Location: UK
Posts: 18,579
Likes: 0
Received 0 Likes
on
0 Posts
Can any AB folk comment on the No1 EPR on both displayed traces? It indicates near 'idle' to me, but is this just a function of the way the FDR or engine measures it in reverse?
Join Date: Mar 2006
Location: Choroni, sometimes
Posts: 1,974
Likes: 0
Received 0 Likes
on
0 Posts
@teropa
Flight recorder data haven't leaked to this forum accidently. Anonymous user fed it in, piece by piece.
If you look to the pprune home page you can find this:
As these are anonymous forums the origins of the contributions may be opposite to what may be apparent. In fact the press may use it, or the unscrupulous, to elicit certain reactions.
Think about it......
If you look to the pprune home page you can find this:
As these are anonymous forums the origins of the contributions may be opposite to what may be apparent. In fact the press may use it, or the unscrupulous, to elicit certain reactions.
Think about it......
Join Date: Sep 2000
Location: Bielefeld, Germany
Posts: 955
Likes: 0
Received 0 Likes
on
0 Posts
hetfield, Right Way Up,
it seems that you object somehow to a public technical discussion of what went on in the accident.
I may suppose that you think that appropriate behavior is for a designated set of "official" investigators to consider data in camera and then to decide on their conclusions and issue them some months to years later.
We don't need to discuss this here, and possibly we shouldn't, but (ignoring this point I would like to point out that there are many weaknesses in this procedure.
First, like all of us, designated investigators are humans and may make mistakes, as investigators themselves know. A wider informed technical discussion helps to avoid some of these mistakes. As many, but not all, investigators also know.
Second, there may be, and often are, special interests which attempt to influence the designated investigators, sometimes successfully, often to the detriment of the scientific quality of the investigation. A wider discussion mitigates the effects of such influence.
Third, the increasing criminalisation of accidents means that when an "official" investigation is finished, sometimes some poor souls receive criminal indictments, based on the official report or other official investigation. They may get off, if various experts can persuade the court that the official report does not tell quite the right story, or the story that the prosecution want to read into it, but even if they do the years that this takes can often destroy their lives. (I have tried already to avoid this particular theme here, but it does seem to have a way of bubbling over.)
And fourth, in this case the Brazilian polity apparently needs to take a collective decision about the future use of Congonhas airport. Figuring out quickly what did and did not go wrong with this accident is likely to support a passable collective decision. Basing such a decision on speculative information, such as would happen if all data on this accident were secret, is unlikely to be as productive for the society as a whole.
Do I also detect a sense that discussing accidents is somehow disrespectful to the victims? I have not found that to be the case. More often, I have found that surviving family members try to make contact with other people who might help them, because they have little or no access to "official" proceedings.
PBL
it seems that you object somehow to a public technical discussion of what went on in the accident.
I may suppose that you think that appropriate behavior is for a designated set of "official" investigators to consider data in camera and then to decide on their conclusions and issue them some months to years later.
We don't need to discuss this here, and possibly we shouldn't, but (ignoring this point
I would like to point out that there are many weaknesses in this procedure. First, like all of us, designated investigators are humans and may make mistakes, as investigators themselves know. A wider informed technical discussion helps to avoid some of these mistakes. As many, but not all, investigators also know.
Second, there may be, and often are, special interests which attempt to influence the designated investigators, sometimes successfully, often to the detriment of the scientific quality of the investigation. A wider discussion mitigates the effects of such influence.
Third, the increasing criminalisation of accidents means that when an "official" investigation is finished, sometimes some poor souls receive criminal indictments, based on the official report or other official investigation. They may get off, if various experts can persuade the court that the official report does not tell quite the right story, or the story that the prosecution want to read into it, but even if they do the years that this takes can often destroy their lives. (I have tried already to avoid this particular theme here, but it does seem to have a way of bubbling over.)
And fourth, in this case the Brazilian polity apparently needs to take a collective decision about the future use of Congonhas airport. Figuring out quickly what did and did not go wrong with this accident is likely to support a passable collective decision. Basing such a decision on speculative information, such as would happen if all data on this accident were secret, is unlikely to be as productive for the society as a whole.
Do I also detect a sense that discussing accidents is somehow disrespectful to the victims? I have not found that to be the case. More often, I have found that surviving family members try to make contact with other people who might help them, because they have little or no access to "official" proceedings.
PBL
PBL,
I do not object to technical discussion on a public board. What I do object to is the release of information that should not be released to the public domain especially before an official investigation is completed. I'd be surprised if there are not some legal ramifications for Pprune for publishing such data. Personally I prefer the idea that people investigating the accident have some sort of qualification other than tapping into the internet.
I do not object to technical discussion on a public board. What I do object to is the release of information that should not be released to the public domain especially before an official investigation is completed. I'd be surprised if there are not some legal ramifications for Pprune for publishing such data. Personally I prefer the idea that people investigating the accident have some sort of qualification other than tapping into the internet.
Join Date: Jul 2007
Location: Germany
Posts: 556
Likes: 0
Received 0 Likes
on
0 Posts
Right Way Up,
It wasn't PPRuNe, who originally put the data in the public domain (i. e. some web site). Once it is out it cannot be put back into the bottle.
So do I. But that group is not limited to the official investigators. Many people here are qualified to interpret the data correctly and draw conclusions from it.
There are many other very important items, such as interviews with involved people (managers, ATC, authorities, ...), inquiries into day-to-day operations at TAM and at the airport, which are not available to us, and these are best left to the people officially tasked with this job.
I agree with PBL's reasons why it may be beneficial to discuss the accident, and all available data, publicly early on [disclaimer: I know PBL personally and have the highest respect for his work].
Bernd
I'd be surprised if there are not some legal ramifications for Pprune for publishing such data.
Personally I prefer the idea that people investigating the accident have some sort of qualification other than tapping into the internet.
There are many other very important items, such as interviews with involved people (managers, ATC, authorities, ...), inquiries into day-to-day operations at TAM and at the airport, which are not available to us, and these are best left to the people officially tasked with this job.
I agree with PBL's reasons why it may be beneficial to discuss the accident, and all available data, publicly early on [disclaimer: I know PBL personally and have the highest respect for his work].
Bernd
Join Date: Sep 2000
Location: Bielefeld, Germany
Posts: 955
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by Right Way Up
What I do object to is the release of information that should not be released to the public domain especially before an official investigation is completed.
Do you have any argument for that "should" that outweighs the points I made?
Originally Posted by Right Way Up
I'd be surprised if there are not some legal ramifications for Pprune for publishing such data
Personally I prefer the idea that people investigating the accident have some sort of qualification other than tapping into the internet
PBL
Join Date: Jul 1999
Location: 58-33N. 00-18W. Peterborough UK
Posts: 3,040
Likes: 0
Received 0 Likes
on
0 Posts
I suspect the real reason for the unease, from some, of the FDR data release is simply because it breaks with tradition. But think it through. Traditionally, FDR data has been kept confidential until an accident report is issued, sometime years. We’d be naive to think that investigators, even with the best will in the word, didn’t use this confidentiality to allow delays – and to, unwittingly, colour their conclusions to suit their personalities.
Far better to get the data out into the open, earliest. After all, it simply reveals what the aircraft was doing at the time. Why it was doing it is another question - for the formal investigation to answer. There’s enough aviation nous on this web, and others, to gain useful and early information from the TAM FDR which may just prevent the analysis of another FDR.
Far better to get the data out into the open, earliest. After all, it simply reveals what the aircraft was doing at the time. Why it was doing it is another question - for the formal investigation to answer. There’s enough aviation nous on this web, and others, to gain useful and early information from the TAM FDR which may just prevent the analysis of another FDR.
Join Date: Aug 2007
Location: The Netherlands
Age: 67
Posts: 288
Likes: 0
Received 0 Likes
on
0 Posts
Investigations
To PBL, on #1473
Excellent analysis of the performance of the crew as far as braking is concerned. The "11 seond delay to start of manual braking" had annoyed me from the first time I encountered it. Didn't have time yet to elaborate on that though, because the job and the wife need some attention too.
To those who seem to view this open source analysis as sort of indecent towards crew or victims- see how PBL described how this crew performed well in most aspects of their task, that is more a way of giving them respect than of dishonouring them.
A belated answer to one who was wondering how a female voice could be registered on the CVR (unfortunately a scream): the cockpit door may be bulletproof these days, but soundproof it is not, to sounds from the (near) cabin.
Best regards.
Edited for typo.
Excellent analysis of the performance of the crew as far as braking is concerned. The "11 seond delay to start of manual braking" had annoyed me from the first time I encountered it. Didn't have time yet to elaborate on that though, because the job and the wife need some attention too.
To those who seem to view this open source analysis as sort of indecent towards crew or victims- see how PBL described how this crew performed well in most aspects of their task, that is more a way of giving them respect than of dishonouring them.
A belated answer to one who was wondering how a female voice could be registered on the CVR (unfortunately a scream): the cockpit door may be bulletproof these days, but soundproof it is not, to sounds from the (near) cabin.
Best regards.
Edited for typo.
Thread Starter
Join Date: May 2005
Location: Brasil
Posts: 351
Likes: 0
Received 0 Likes
on
0 Posts
Gents
Please remember that, although CVR/FDR data is sometimes released once an investigation is completed, this case is a political hot potato and several parties are more interested in backing up their arguments than actually getting at the truth of the matter.
The air force, charged with the investigation, are not at all happy with the interference that they are getting, the refusal of a senior officer to testify before one of the political inquiries shows that. The air force will conduct a thoroughly professional accident investigation, asking for international assistance when they feel that it is needed, and their final report will be all that the aviation community expects. It will, as these things always do, take months to complete.
Public interest will have waned long before that date, and many parties are using this tragedy to further their own interests, so we are seeing the release of normally confidential data in a way that is bordering on the repugnant.
However, once it is in the public domain there is no putting it back, and at least on Pprune it can be discussed in a relatively professional manner, thanks to individuals like ELAC, PBL, PJ2 and several others. I, for one, find this discussion interesting and educational (having been involved in a number of accident investigations over the years) but I can quite understand those who think that this shouldn't be a topic for armchair investigators.
Please remember that, although CVR/FDR data is sometimes released once an investigation is completed, this case is a political hot potato and several parties are more interested in backing up their arguments than actually getting at the truth of the matter.
The air force, charged with the investigation, are not at all happy with the interference that they are getting, the refusal of a senior officer to testify before one of the political inquiries shows that. The air force will conduct a thoroughly professional accident investigation, asking for international assistance when they feel that it is needed, and their final report will be all that the aviation community expects. It will, as these things always do, take months to complete.
Public interest will have waned long before that date, and many parties are using this tragedy to further their own interests, so we are seeing the release of normally confidential data in a way that is bordering on the repugnant.
However, once it is in the public domain there is no putting it back, and at least on Pprune it can be discussed in a relatively professional manner, thanks to individuals like ELAC, PBL, PJ2 and several others. I, for one, find this discussion interesting and educational (having been involved in a number of accident investigations over the years) but I can quite understand those who think that this shouldn't be a topic for armchair investigators.
I suspect the real reason for the unease, from some, of the FDR data release is simply because it breaks with tradition. But think it through. Traditionally, FDR data has been kept confidential until an accident report is issued, sometime years.
We’d be naive to think that investigators, even with the best will in the word, didn’t use this confidentiality to allow delays – and to, unwittingly, colour their conclusions to suit their personalities.
Investigating teams release the information after the various personalities feel that they agree that the data points are valid. There are no lingering personality traits left in the agreed data points.
Far better to get the data out into the open, earliest. After all, it simply reveals what the aircraft was doing at the time. Why it was doing it is another question - for the formal investigation to answer. There’s enough aviation nous on this web, and others, to gain useful and early information from the TAM FDR which may just prevent the analysis of another FDR.
Join Date: Sep 2000
Location: Bielefeld, Germany
Posts: 955
Likes: 0
Received 0 Likes
on
0 Posts
A certain amount of discussion of the whys and wherefores of putting data in the public domain is worthwhile. However, we should recognise that the Congonhas FDR data release itself is a moot point. I have been informed that it has been released to the public by the Brazilian aviation authorities.
PBL
PBL