TAM A320 crash at Congonhas, Brazil
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Originally Posted by bsieker
A/THR is a lot more complex than I imagined. 
Instead, the big picture will be handled differently, and the safety net of statistics "there is no evidence to suggest that..." will be relied upon while everyone gets up to speed to varying degrees. Hidden fingers will be kept on pulses, lawyers will have a superbly lucrative couple of years and the patient will be declared to be in reasonable continuing health I guess.
I am not dismissing those thoroughly experienced pilots who do understand all the foibles, nor the statistics of hundreds of thousands of hours of relative normality, but you Bernd are a member of a world leading working group of scientists, are you not, whose main field of expertise is Safety of Computers and Automation in Commercial Aircraft Systems? And you have been studying the factors in this a full 7 days a week lately, yet you too are confused by this particular A/THR system?
And to PBL, thank you for coming back here to respond. Does the A/THR logic confuse you too?
Professional Pilots don't have to understand realtime embedded safety critical systems theory in any real depth, but they are supposed to understand Boolean logic. That said, I am pretty certain they can pass ATPL exams and AB type ratings without really understanding more than just some of the rudiments. If I am right, when it comes to the logic in these Thrust Lever circuits those pilots are trusting somewhat blindly on a whole raft of non-absolutes in their knowledge i.e. latest FCOM not Warsaw FCOM as PBL points out, instruction, their own observations, a comprehensive set of system warnings of error states, reputation and 'safety in numbers' of the particular type, and finally that virtual safety net of statistics of hundreds of thousands of hours of relative normality. Fair enough, if their trust is well placed. We can't all be rocket scientists, brain surgeons or top-flight engineers who "know" what they are doing versus "know" what they were told had to be learned.
So is this culture where we carry on with the same rules, but just market/change the emphasis on the product small print a little bit, really conducive to the sort of aviation industry we all want right now? Or do we want money spent on more highly qualified pilots or on more gracefully failsafe systems interfaces, or on less unforgiving runways ? So far, it seems we can't even afford a day on the ground to compare notes, such is the need for the flywheel of progress to keep turning.
PBL introduces the concept of prioritisation or ranking of uncertainties. It wasn't of course intended to be an answer to my "what is the desired culture" question just now, but I would say that I think the Frank Ramsay concept plays too soon into the hands of the accountants and lawyers when used in summarising this kind of investigation, at this stage anyway.
Earlier I indicated some small common ground between systems development (or rather 'developers') in the financial world and in aviation. I would hate to see the two cultures converge even further. To use the gambling terminology, I used to say I could without fear or stress bet my life on all my activities in one and that I respected the other, but now I am not quite as certain as I once was. I shall read on with interest.
Last edited by slip and turn; 13th Aug 2007 at 11:43. Reason: ... almost forgot the unforgiving runways for a moment.
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What chance do mere pilots have of fully understanding it before they go to work today?
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Originally Posted by slip and turn
What chance do mere pilots have of fully understanding it before they go to work today?
The particular case that puzzles me is an abnormal situation, in which an "unvoluntary A/THR disconnect" occurs. Pilots wouldn't need to know anything other than that it did occur and what to do about it (signalled by the FMA and ECAM messages "THR LK" and "THRUST LEVERS .... MOVE"). The internal workings aren't in the FCOM, and neither should they be, since this is the "operating" manual. The only information on this I could get was from the Airbus response in the Appendix of the GE 536 (Taipei over-run) report. It is very concise, and I have to read and re-read it to fully understand.
I still noticed another thing: Unvoluntary A/THR disconnect should produce a single chime; A/THR disconnected at or around 18:48:29, but no chime is in the CVR transcript. Maybe only an oversight in the transcription.
but you Bernd are a member of a world leading working group of scientists, are you not, whose main field of expertise is Safety of Computers and Automation in Commercial Aircraft Systems?
Last edited by bsieker; 13th Aug 2007 at 12:42. Reason: Straightened some paragraphs.
How many airbus pilots had even heard of the Transasia accident before this one happened. Following that, the only way most people would see the post TAM airbus telex would have been through PPrune. If the TAM pilot had been aware of the Transasia accident the chances are that this one would never have happened. I reckon there is a lot of info that is not getting down the chain from the manufacturers/investigation boards!
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A/THR again
I understand that at diminishing airspeed there is an increasing EPR target that A/THR tries to set to set on the engine(s),
but #2 was in CL detent, and surely one engine at CLIMB power would be enough to maintain 140kts even in CONF FULL.
So I deduce that the limiting thrust lever EPR limit must have been that from thrust lever #1.
I don't have the ball park figure values on the Delta needed to trigger the A/THR disconnect (flying a different engine), I estimate it ~.2 EPR.
In resume, you would have to consider :
1.FMGS-->EIU-->FADEC--> = FADEC Target EPR
2.TLA---------->FADEC computed TLA/EPR
3.ADR--> + TLA----------> = EPR limit (depends on ambient conditions )
and compare them permanently.
People who can be confused with this architecture are people whose job is not a permanent contact with it. What is needed is a modicum of open-mindedness - sorely lacking in some parts of this forum !
The basic philosophy is "if you want the automatics, set them properly. If you don't, there are some warnings that will remind you to follow the correct procedure. If you insist,the automatics will disconnect and will deliver a configuration that's as safe as it can so that you can sort it out. And make sure that the warnings are unmissable and unmistakable".
Finally, there is still around the misconception that the CLB detent will deliver *Climb thrust*. Just treat it as a TLA at which the max achieved thrust will be CLB EPR on the conditions of the day.
In normal operations, a pilot will never see a climb EPR except after take-off, and then for a few moments, as the A/THR will then have engaged.
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Each engine has its own -independent- two-channel FADEC.What is computed on #1 FADEC may be - and generally is - different from what #2 does.
I don't have the ball park figure values on the Delta needed to trigger the A/THR disconnect (flying a different engine), I estimate it ~.2 EPR.
The bottom line is: A/THR disconnects when a thrust reverser is deployed.
It goes as follows:
- TLA readout corresponds to a certain EPR value
- TLA target EPR value is upper limit for autothrust
- A/THR working normally in speed mode, using engine #2
- TL #1 set to idle. No problem, just limits thrust usable by A/THR to idle
for that engine.
- TLA EPR value for Eng #1 becomes 0.98
- TL #1 set to reverse:
. TLA EPR becomes NCD ("no computed data")
. FMGC continues to use last valid value (0.98)
. FADEC uses a value of 0.75 with engine in reverse (FADEC EPR target feedback is upper limited to EPR TLA, EPR IDLE is reduced by 0.2 when reverser is deployed more than 15% (0.98 - 0.2 makes 0.78, but I assume that's close enough))
. comparison of the two values (0.98 and 0.75) is greater than 0.15.
. if that condition persists for more than 1.8s, A/THR disconnects.
This is consistent with the observed behaviour in the FDR graphs that A/THR disconnects about 2s after the thrust reverser was fully deployed on engine #1, at which time also EPR on engine #2 freezes.
Finally, there is still around the misconception that the CLB detent will deliver *Climb thrust*.
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I have enjoyed remaining a silent lurker throughout this thread. Until now that is... so stand by for yet another non-pilot sounding off, albeit in the hope that he won't be knocked on his ass for doing so.
My field of study was Psychology, and whilst I don't presume to judge what occurred in this crash I do have a couple of observations to offer from my own perspective.
Human cognition (taken as the psychological result of perception and learning and reasoning) is complex and fascinating. At times it can be at least as counter-intuitive as any other complex system, even though it has been endlessly refined towards human survival. There is no more effective demonstration of what an inside knowledge of human cognition can achieve than to see a good up-close magician - through deliberate mis-cues and misdirection an apparently intuitive situation can become bizarre, with the impossible apparently occurring or the inevitable failing to occur. In such situations you arrive knowing someone will try to fool you, on your guard, but still end up bamboozled.
Effective cognitive misdirection is typically founded in extremely familiar scenarios or easy tasks, in which confusion is created between cause and effect. When the magician urges you to check very very carefully that the cup is empty and there is nothing in his pocket, it's because the ball is pinched between two fingers at the back of his hand. Yet the more carefully he gets you to check, the more amazed you are when the ball appears. A secondary part of this technique is momentum - the magician will stand very close, keep talking, showing, pointing, setting tasks and suggesting conclusions to draw. There is 'no time to think'.
It's not surprising that experienced pilots are incredulous that an experienced pilot could possibly fail in a safety-critical task which is elementary to every landing, especially given that the same crew had already landed successfully with a rev inop. I'm sure that certainty was shared by the unfortunate crew of the aircraft which crashed. Whatever truly happened, that's the kind of everyday certainty which both cognitive psychologists and magicians know to be the mainstay of misdirection. Without that certainty, the misdirection could not occur, it is what fuels it.
So here's a hypothetical from a psych viewpoint.
Crew learn rev inop. This is fairly unusual and thus gets some attention. Undertake flight, on approach there is the reminder 'rev inop'. Upon landing everything seems fine. It is fine. 'Rev inop' is no big deal.
Next flight. Rev inop. OK, mustn't forget but it's no longer news. The new task (rev inop) is becoming familiar and is being incorporated in a very very familiar task (TL retard at landing). This is where human cognition can offer pitfalls: making alterations to an everyday task which is genuinely, in itself, simple. If a momentary task is muddled through a complex blend of familiarity with unfamiliarity, it is the very simplicity and ease of the task in itself which contributes both to the error and to the difficulty of later diagnosing what has gone wrong.
If we allow that this could occur (not that it is likely to happen on any one flight but that it is conceivable to ever happen at all) we are now in a whole world of classic misdirection. The runway is flagged as slippery, so expectation of this possibility is conscious. Also known is that the runway is short. The TLs are not a concern, they are familiar and proven good, even with the rev inop. On landing, there is an immediate and alarming DECEL problem. Where will attention go? Slippery runway. Length of runway. Now systems are not triggering: spoilers, auto-braking. Why are they not deploying? TLs are in the past, before everything went crazy.
It seems that in this rare situation, auto-thrust is giving an extra push to a fast closing door: not only are braking systems not being triggered but one engine is spooling up. This is a consequence of the TL error which is, in the moment, entirely outside the crews sphere of awareness. Circumstances have misdirected them to lack of braking rather than over-thrust, both because of
1. where in the time line the problems occur
2. the warning of a slippery runway
3. the implicit belief that 'TLs are so easy and obvious that nobody gets them wrong'.
One Pontification (which I am unqualified to make but heck this is only the internet):
If the the above described human error did occur, the Airbus system exacerbated an error for which circumstances left little margin. That does not mean that Airbus are necessarily in error or inferior, but there is surely a case for examining whether the auto thrust / braking logic trees could be refined. Of course, many may believe that this apparent crew error did not occur...
Final Pontification (from a psych viewpoint of which I really am quite confident):
Being absolutely certain you would never ever make an elementary mistake is in itself dangerous.
My field of study was Psychology, and whilst I don't presume to judge what occurred in this crash I do have a couple of observations to offer from my own perspective.
Human cognition (taken as the psychological result of perception and learning and reasoning) is complex and fascinating. At times it can be at least as counter-intuitive as any other complex system, even though it has been endlessly refined towards human survival. There is no more effective demonstration of what an inside knowledge of human cognition can achieve than to see a good up-close magician - through deliberate mis-cues and misdirection an apparently intuitive situation can become bizarre, with the impossible apparently occurring or the inevitable failing to occur. In such situations you arrive knowing someone will try to fool you, on your guard, but still end up bamboozled.
Effective cognitive misdirection is typically founded in extremely familiar scenarios or easy tasks, in which confusion is created between cause and effect. When the magician urges you to check very very carefully that the cup is empty and there is nothing in his pocket, it's because the ball is pinched between two fingers at the back of his hand. Yet the more carefully he gets you to check, the more amazed you are when the ball appears. A secondary part of this technique is momentum - the magician will stand very close, keep talking, showing, pointing, setting tasks and suggesting conclusions to draw. There is 'no time to think'.
It's not surprising that experienced pilots are incredulous that an experienced pilot could possibly fail in a safety-critical task which is elementary to every landing, especially given that the same crew had already landed successfully with a rev inop. I'm sure that certainty was shared by the unfortunate crew of the aircraft which crashed. Whatever truly happened, that's the kind of everyday certainty which both cognitive psychologists and magicians know to be the mainstay of misdirection. Without that certainty, the misdirection could not occur, it is what fuels it.
So here's a hypothetical from a psych viewpoint.
Crew learn rev inop. This is fairly unusual and thus gets some attention. Undertake flight, on approach there is the reminder 'rev inop'. Upon landing everything seems fine. It is fine. 'Rev inop' is no big deal.
Next flight. Rev inop. OK, mustn't forget but it's no longer news. The new task (rev inop) is becoming familiar and is being incorporated in a very very familiar task (TL retard at landing). This is where human cognition can offer pitfalls: making alterations to an everyday task which is genuinely, in itself, simple. If a momentary task is muddled through a complex blend of familiarity with unfamiliarity, it is the very simplicity and ease of the task in itself which contributes both to the error and to the difficulty of later diagnosing what has gone wrong.
If we allow that this could occur (not that it is likely to happen on any one flight but that it is conceivable to ever happen at all) we are now in a whole world of classic misdirection. The runway is flagged as slippery, so expectation of this possibility is conscious. Also known is that the runway is short. The TLs are not a concern, they are familiar and proven good, even with the rev inop. On landing, there is an immediate and alarming DECEL problem. Where will attention go? Slippery runway. Length of runway. Now systems are not triggering: spoilers, auto-braking. Why are they not deploying? TLs are in the past, before everything went crazy.
It seems that in this rare situation, auto-thrust is giving an extra push to a fast closing door: not only are braking systems not being triggered but one engine is spooling up. This is a consequence of the TL error which is, in the moment, entirely outside the crews sphere of awareness. Circumstances have misdirected them to lack of braking rather than over-thrust, both because of
1. where in the time line the problems occur
2. the warning of a slippery runway
3. the implicit belief that 'TLs are so easy and obvious that nobody gets them wrong'.
One Pontification (which I am unqualified to make but heck this is only the internet):
If the the above described human error did occur, the Airbus system exacerbated an error for which circumstances left little margin. That does not mean that Airbus are necessarily in error or inferior, but there is surely a case for examining whether the auto thrust / braking logic trees could be refined. Of course, many may believe that this apparent crew error did not occur...
Final Pontification (from a psych viewpoint of which I really am quite confident):
Being absolutely certain you would never ever make an elementary mistake is in itself dangerous.
Last edited by robdean; 13th Aug 2007 at 14:21.
I still noticed another thing: Unvoluntary A/THR disconnect should produce a single chime; A/THR disconnected at or around 18:48:29, but no chime is in the CVR transcript. Maybe only an oversight in the transcription
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robdean... I have commented above that this is going to be "trick cyclists" investigation 
Your analysis is probably along the right lines IMHO... and deeper than most of us aeroplane types can understand
This Airbus system has been around a long time... and generally successful. Changing it introduces other risks, and what's more takes a long time (and £££ / $$$$)
I am unaware of any other "failure to close TL(s)" incidents / accidents except with the TR Inop scenario. You have given us the psychobabble of how that drill maybe led to the next "error"... If one was to change, as Airbus have done, the first part - namely a "non-standard operation involving just 1 TL" - does this maybe solve the human factors part?
In fact, the new Airbus procedure says to select both TLs to Full Reverse. This also applies the current logic trees in a different way, making the chance of no ABrk / Gnd Spoliers less likely...
NoD
Your analysis is probably along the right lines IMHO... and deeper than most of us aeroplane types can understand
If the the above described human error did occur, the Airbus system exacerbated an error for which circumstances left little margin. That does not mean that Airbus are necessarily in error or inferior, but there is surely a case for examining whether the auto thrust / braking logic trees could be refined.
I am unaware of any other "failure to close TL(s)" incidents / accidents except with the TR Inop scenario. You have given us the psychobabble of how that drill maybe led to the next "error"... If one was to change, as Airbus have done, the first part - namely a "non-standard operation involving just 1 TL" - does this maybe solve the human factors part?
In fact, the new Airbus procedure says to select both TLs to Full Reverse. This also applies the current logic trees in a different way, making the chance of no ABrk / Gnd Spoliers less likely...
NoD
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Robdean,
thank you for that insightful post.
I think I've seen some of the things I've posted before reflected here.
The main theme to me would be: build the automation around human capabilities rather than try to teach humans to accept the way the automation works.
When you say that by the time they were on the ground and spoilers were not deploying and brakes were not working, the thrust lever was a thing of the past, I think this should lead to a critical design rule when working with security related systems where a human has to decide in seconds:
One function - one dedicated control.
In this critical situation, asking people to memorize the GS/AB logic as solely coupled to the thrust levers clearly requires more brain cycles and, more than that, higher brain functions than "no spoilers - manual spoiler override lever". We are extremely good at learning simple "stimulus - action" tasks into what is called "procedural memory" while situational analysis requires knowledge that is accessed in "declarative memory". Much slower, much more prone to error and forgetfulness (we don't forget what is in declarative memory, like riding a bicycle or, actually, flying a plane) but sometime we do forget how things are tied together under the hood.
pj
thank you for that insightful post.
I think I've seen some of the things I've posted before reflected here.
The main theme to me would be: build the automation around human capabilities rather than try to teach humans to accept the way the automation works.
When you say that by the time they were on the ground and spoilers were not deploying and brakes were not working, the thrust lever was a thing of the past, I think this should lead to a critical design rule when working with security related systems where a human has to decide in seconds:
One function - one dedicated control.
In this critical situation, asking people to memorize the GS/AB logic as solely coupled to the thrust levers clearly requires more brain cycles and, more than that, higher brain functions than "no spoilers - manual spoiler override lever". We are extremely good at learning simple "stimulus - action" tasks into what is called "procedural memory" while situational analysis requires knowledge that is accessed in "declarative memory". Much slower, much more prone to error and forgetfulness (we don't forget what is in declarative memory, like riding a bicycle or, actually, flying a plane) but sometime we do forget how things are tied together under the hood.
pj
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http://www-verimag.imag.fr/SYNCHRONE/history.pdf
The logic was written in a real-time language formulated especially for the task. I'm nowhere near as current or academic as bsieker or PBL, but my Software Reliability lecturer was Peter Mellor, who was about as knowledgeable about the subject as anyone.
I do know enough to say that the concept of programming that kind of realtime system is about as far away from the Imperative or Declarative paradigms used in 99% of everyday computing applications as it is possible to get.
My experience of the A320 story was that the problems came about as much from knee-jerk reactions from a certain breed of pilot...
as it did the assumption by Airbus's sales people (*not* their engineers) that the human brain would not be able to find a way around their 'failsafe' system.
In this particular case, it looks like a split-second mistake by an experienced crew may have had tragic consequences. You can try to dig for faults in the logic and the design all you like, but it's going to work out the same every time - for whatever reason they did it, leaving the TL significantly forward of the IDLE position sealed their fate.
The logic was written in a real-time language formulated especially for the task. I'm nowhere near as current or academic as bsieker or PBL, but my Software Reliability lecturer was Peter Mellor, who was about as knowledgeable about the subject as anyone.
I do know enough to say that the concept of programming that kind of realtime system is about as far away from the Imperative or Declarative paradigms used in 99% of everyday computing applications as it is possible to get.
My experience of the A320 story was that the problems came about as much from knee-jerk reactions from a certain breed of pilot...
I'm not a schoolboy, I'm a trained 727 captain. In that case I do not need to be here. I'll go back to Hamburg and fly your crate.
In this particular case, it looks like a split-second mistake by an experienced crew may have had tragic consequences. You can try to dig for faults in the logic and the design all you like, but it's going to work out the same every time - for whatever reason they did it, leaving the TL significantly forward of the IDLE position sealed their fate.
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Originally Posted by Right Way Up
A quick look in my FCOM shows an ECAM of "AUTO FLT A/THR OFF" with a chime if autothrust is disconnected any way other than instinctive disconnect or BOTH thrust levers idle. However this message is inhibited between touchdown & 80 kts
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<<<leaving the TL significantly forward of the IDLE position sealed their fate.>>>
Dozy:
it would be bad for any kind of plane, not just an airbus...but one wonders if the spoilers could be deployed regardless of thrust lever position if some poor souls might still be breathing.
I just imagine if every car maker in the world, suddenly decided that the gas peddle should be operated by the left foot, instead of the right, that we would soon see more accidents.
Dozy:
it would be bad for any kind of plane, not just an airbus...but one wonders if the spoilers could be deployed regardless of thrust lever position if some poor souls might still be breathing.
I just imagine if every car maker in the world, suddenly decided that the gas peddle should be operated by the left foot, instead of the right, that we would soon see more accidents.
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ECAM Takeoff Memo
ELAC,
I had to think about that for some time ...
I'm looking at the page in the FCOM now.
T.O Memo consist of:
AUTO BRK ... MAX
SIGNS ... ON
CABIN ... CHECK
SPLRS ... ARM
FLAPS ... T.O
T.O CONFIG ... TEST
These are the items shown in the FCOM screen shot. Are there more?
If I do all the stuff (how do I tell the computer I've checked the cabin, btw?) that is displayed, except arm the ground spoilers, you say then that, although the SPLRS line may remain blue (to do), T.O Config might still change to "NORMAL", since it only checks for "Spoilers retracted", but not for "Ground Spoilers Armed"?
Bernd
I had to think about that for some time ...
Originally Posted by ELAC
The armed condition of the spoilers is shown on the ECAM Takeoff Memo and checking it is a part of every take-off. The line "SPLRS.......Arm" is shown in blue until the PNF arms them at which time the memo becomes green.
Also a part of the memo is the line "T/O Config.....Test". This simulates a takeoff and checks the configuration of required systems, including spoiler position, but not whether the ground spoilers are armed. If all items are correctly configured the line changes to "T/O Config....Normal" in green.
Also a part of the memo is the line "T/O Config.....Test". This simulates a takeoff and checks the configuration of required systems, including spoiler position, but not whether the ground spoilers are armed. If all items are correctly configured the line changes to "T/O Config....Normal" in green.
T.O Memo consist of:
AUTO BRK ... MAX
SIGNS ... ON
CABIN ... CHECK
SPLRS ... ARM
FLAPS ... T.O
T.O CONFIG ... TEST
These are the items shown in the FCOM screen shot. Are there more?
If I do all the stuff (how do I tell the computer I've checked the cabin, btw?) that is displayed, except arm the ground spoilers, you say then that, although the SPLRS line may remain blue (to do), T.O Config might still change to "NORMAL", since it only checks for "Spoilers retracted", but not for "Ground Spoilers Armed"?
Bernd
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TripleBravo Post #1587:
And in addition you have 6 potentiometers whitch give the TLA to the SECs (for flight control system)
The position information is transmitted by 6 cables per sensor, which allow to cross-check for cable breaks and potentiometer breakups for each sensor. These analog signals are fed into one channel of FADEC (A), the other 6 from the second sensor are treated completely separate in channel B. The arbitration between the two FADEC channels takes place after input check and evaluation of the signals. Each channel is capable to control the engine on its own if the other fails. They are independent, also physically, which means that every chip is only responsible for one of the two channels.
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These are the items shown in the FCOM screen shot. Are there more?
If I do all the stuff (how do I tell the computer I've checked the cabin, btw?) that is displayed, except arm the ground spoilers, you say then that, although the SPLRS line may remain blue (to do), T.O Config might still change to "NORMAL", since it only checks for "Spoilers retracted", but not for "Ground Spoilers Armed"?
If I do all the stuff (how do I tell the computer I've checked the cabin, btw?) that is displayed, except arm the ground spoilers, you say then that, although the SPLRS line may remain blue (to do), T.O Config might still change to "NORMAL", since it only checks for "Spoilers retracted", but not for "Ground Spoilers Armed"?
Some items, notably the cabin item are pin selectable. Some airline's have them on the takeoff memo, some don't. Two companies I've worked for did not use this item, the third uses a slightly modified version where the item is not on the takeoff memo but signalled seperately by the purser producing a "CABIN READY" advisory message which shows up on the rights side of the upper ECAM. Where the cabin check item is on the takeoff memo I would expect that it would turn green in response to the same purser input that is used to generate the "CABIN READY" message.
Regarding whether the Config test will turn green if the spoilers are not armed, I am doing recurrent sim at the moment so I will try to remember to try it out tomorrow and let you know the result.
ELAC
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To A320 flyers out there: Would risking stowage problems on #1 (plus the precious seconds it takes) be better on a take off attempt or would it be better in this case to shut down #1 and TOGA on #2. Would this plane have been able to lift off at 62tons from the remainder of the runway (being at the speed it was at already). I understand wasted seconds and disaster should a T/R not stow are the main reasons that its not usually a good idea to attempt to take off once T/R is activated.
Perhaps with moving TLs, the AT would have advanced TL#1 as thrust was added to maintain airspeed as TL#2 was brought to idle and provided a peripheral vision clue at the time the mistake was being made.
While considerable incredulity has been expressed that both TLs were not brought to idle, we see that other crews have fallen into the same trap, albeit with lesser consequence.
Suppression of the AT disconnect chime at this time contributes to the insidious nature of landing with an advanced TL. There do not seem to be any obvious immediate clues.
The record shows it takes several seconds for a crew in such a situation to realise they are not slowing down properly. There does not seem to be enough time to diagnose the problem before going off the end, although it would be interesting to hear from any crews who have effectively recovered from this situation.
I disagree that the crew's fate was sealed by not idling TL#1 as until reverse was selected, they had the option of taking it back up.
Not being able to select reverse unless both TLs were in idle might prevent a crew from painting itself into a similar corner.
While considerable incredulity has been expressed that both TLs were not brought to idle, we see that other crews have fallen into the same trap, albeit with lesser consequence.
Suppression of the AT disconnect chime at this time contributes to the insidious nature of landing with an advanced TL. There do not seem to be any obvious immediate clues.
The record shows it takes several seconds for a crew in such a situation to realise they are not slowing down properly. There does not seem to be enough time to diagnose the problem before going off the end, although it would be interesting to hear from any crews who have effectively recovered from this situation.
I disagree that the crew's fate was sealed by not idling TL#1 as until reverse was selected, they had the option of taking it back up.
Not being able to select reverse unless both TLs were in idle might prevent a crew from painting itself into a similar corner.
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To A320 flyers out there: Would risking stowage problems on #1 (plus the precious seconds it takes) be better on a take off attempt or would it be better in this case to shut down #1 and TOGA on #2. Would this plane have been able to lift off at 62tons from the remainder of the runway (being at the speed it was at already). I understand wasted seconds and disaster should a T/R not stow are the main reasons that its not usually a good idea to attempt to take off once T/R is activated.
In professional flying, there is no answer to some things. I might have my opinions of the questions you ask, but they are not relevant. It is not a trained for procedure, there are no performance guides for it, it should not be considered (especially in advance) by anyone.
Hope my viewpoint is clear enough
NoD
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Rananim,
Last time I looked if you fail to set QNH corrrectly on either a Boeing or an Airbus, there is absolutely nothing to stop you flying into the ground is there (assuming you choose to ignore your EGPWS warnings....but that is another story)?
That is the fault of who exactly?
You'd think in this day and age altimeters would set themselves wouldn't you?
If you import English idiom into French, you get gobble-de-gook.
Use FORTRAN syntax when coding Matlab and your code will not execute.
I think robdean is about right....because, as PBL mentions, the chances of the other options being considerations are, statistically, about nil.
Personally I think the thread has run its course because in the absence of a member(s) from the Airbus FCS system design team, the speculation by some on the low level design isn't helping anyone.
However, at a higher level, I'm impressed by some of the minds on the thread and their contributions, and the absence of much of the normal "if you're not a pilot you don't understand" vitriole that seems to emanate from some quarters.
Personally, as a long time member of the PPRune WWW site (first came across it when doing my own PhD), I reckon its one of the best threads I've read in ~10 years of membership.
I've always been of the opinion as a pilot, that, you can never have too much knowledge of your aircraft, or for that matter, someone elses.
One day that small bit of information might save you.
Now I'm off to study the Why-Because? technique!
Last time I looked if you fail to set QNH corrrectly on either a Boeing or an Airbus, there is absolutely nothing to stop you flying into the ground is there (assuming you choose to ignore your EGPWS warnings....but that is another story)?
That is the fault of who exactly?
You'd think in this day and age altimeters would set themselves wouldn't you?
If you import English idiom into French, you get gobble-de-gook.
Use FORTRAN syntax when coding Matlab and your code will not execute.
I think robdean is about right....because, as PBL mentions, the chances of the other options being considerations are, statistically, about nil.
Personally I think the thread has run its course because in the absence of a member(s) from the Airbus FCS system design team, the speculation by some on the low level design isn't helping anyone.
However, at a higher level, I'm impressed by some of the minds on the thread and their contributions, and the absence of much of the normal "if you're not a pilot you don't understand" vitriole that seems to emanate from some quarters.
Personally, as a long time member of the PPRune WWW site (first came across it when doing my own PhD), I reckon its one of the best threads I've read in ~10 years of membership.
I've always been of the opinion as a pilot, that, you can never have too much knowledge of your aircraft, or for that matter, someone elses.
One day that small bit of information might save you.
Now I'm off to study the Why-Because? technique!