TAM A320 crash at Congonhas, Brazil
The discussion drifts back to automation and system design, but these may not be significant contributors to the “cause” of the accident.
Using the description of an accident as “a collection of seemingly unconnected contributing factors, where the absence of any one would have avoided it”, then from the information presented so far there appears to have been a high probability of overrunning without the human-thrust lever problems.
It can be assumed that the crew were familiar with moving the thrust levers rearwards and selecting reverse – they did it on every normal landing. Failure to retard the TL would probably be detected by the inability to select / lack of reverse – similar to other aircraft types. I discount the Retard call as auditory sensing is weak and usually the first sense to deteriorate with high workload, stress, fatigue, etc.
The specific difference in this landing was that one reverse was inoperative. The crew procedure required both TL to be selected to reverse in the same way as in normal operations,this provides normal detecting / monitoring cues for erroneous operation. The ‘error’ appears to originate the use of a non-standard or old procedure. Although the lack of reverse was in the briefing, the exact procedure was not discussed which deprived the handling pilot opportunity to visualise his intended actions (recall and refresh from memory), and for the monitoring pilot to both understand the ‘plan’ (what he would be monitoring) and an opportunity to interject if the briefed procedure was incorrect. The possibility that neither crew member knew of the revised procedure remains open, but they had landed in this configuration previously – what procedure was used then? Thus the error may have involved a failure to recall / monitor actions after touchdown, probably due to human factors issues, which could have been exacerbated by stress induced by a demanding (risky) situation.
Post#1893 reports an earlier A320 incident; considering the previous ATR incident and an earlier excursion with a 737, then the indications of this operation was one of high risk. Only a small change in the circumstances could have resulted in any aircraft experiencing an overrun:- heavier rainfall, worn tyres, a little more rubber on the runway, higher weight, longer touchdown point, less wind, and of course an MEL item effecting retardation.
So why didn’t everyone get upset about the 737 excursion; … non fatal? Were crew fortunate or skilled in being able to turn onto the grass preventing the drop onto the road, which perhaps reflects the difference between an ‘overrun’ incident and a fatal accident? Did the other A320 (#1893) ‘depend’ on reverse for a safe landing or the 737 use a computed landing distance based on reverse (cf Midway)?
Thus from this aspect it could be argued that human-thrust lever interface only contributed to the severity of the accident and was not “a causal” contribution. The MEL’ed reverse and associated procedure appears to be more important.
So why didn’t the 737 overrun (or previous ATR, F100 incidents) ring the safety alarm bells, trigger a risk assessment and the reconsideration of operations during the temporary conditions affecting the runway?
Why did the TAM overrun generate 1900+ PPrune posts vs 11 for the 737? Are we misjudging the important aspects of safety, being biased by fatalities, or incorrectly focussing on the ‘bright’ or emotive aspects of automation?
The apparent discarding of near misses without learning from them will perpetuate the risks for others, and as in this case with more severe results. Are we inadvertently thinking that the 737 event or similar “couldn’t happen to us” or “I wouldn’t make that mistake”; and then when we err, we look to the tools for ‘blame’ and not the human contribution.
The risk assessment reflected in this thread appears to be biased, if true then is this due to a failure in our beliefs, knowledge, training, safety management culture or just another facet of human behaviour?
Using the description of an accident as “a collection of seemingly unconnected contributing factors, where the absence of any one would have avoided it”, then from the information presented so far there appears to have been a high probability of overrunning without the human-thrust lever problems.
It can be assumed that the crew were familiar with moving the thrust levers rearwards and selecting reverse – they did it on every normal landing. Failure to retard the TL would probably be detected by the inability to select / lack of reverse – similar to other aircraft types. I discount the Retard call as auditory sensing is weak and usually the first sense to deteriorate with high workload, stress, fatigue, etc.
The specific difference in this landing was that one reverse was inoperative. The crew procedure required both TL to be selected to reverse in the same way as in normal operations,this provides normal detecting / monitoring cues for erroneous operation. The ‘error’ appears to originate the use of a non-standard or old procedure. Although the lack of reverse was in the briefing, the exact procedure was not discussed which deprived the handling pilot opportunity to visualise his intended actions (recall and refresh from memory), and for the monitoring pilot to both understand the ‘plan’ (what he would be monitoring) and an opportunity to interject if the briefed procedure was incorrect. The possibility that neither crew member knew of the revised procedure remains open, but they had landed in this configuration previously – what procedure was used then? Thus the error may have involved a failure to recall / monitor actions after touchdown, probably due to human factors issues, which could have been exacerbated by stress induced by a demanding (risky) situation.
Post#1893 reports an earlier A320 incident; considering the previous ATR incident and an earlier excursion with a 737, then the indications of this operation was one of high risk. Only a small change in the circumstances could have resulted in any aircraft experiencing an overrun:- heavier rainfall, worn tyres, a little more rubber on the runway, higher weight, longer touchdown point, less wind, and of course an MEL item effecting retardation.
So why didn’t everyone get upset about the 737 excursion; … non fatal? Were crew fortunate or skilled in being able to turn onto the grass preventing the drop onto the road, which perhaps reflects the difference between an ‘overrun’ incident and a fatal accident? Did the other A320 (#1893) ‘depend’ on reverse for a safe landing or the 737 use a computed landing distance based on reverse (cf Midway)?
Thus from this aspect it could be argued that human-thrust lever interface only contributed to the severity of the accident and was not “a causal” contribution. The MEL’ed reverse and associated procedure appears to be more important.
So why didn’t the 737 overrun (or previous ATR, F100 incidents) ring the safety alarm bells, trigger a risk assessment and the reconsideration of operations during the temporary conditions affecting the runway?
Why did the TAM overrun generate 1900+ PPrune posts vs 11 for the 737? Are we misjudging the important aspects of safety, being biased by fatalities, or incorrectly focussing on the ‘bright’ or emotive aspects of automation?
The apparent discarding of near misses without learning from them will perpetuate the risks for others, and as in this case with more severe results. Are we inadvertently thinking that the 737 event or similar “couldn’t happen to us” or “I wouldn’t make that mistake”; and then when we err, we look to the tools for ‘blame’ and not the human contribution.
The risk assessment reflected in this thread appears to be biased, if true then is this due to a failure in our beliefs, knowledge, training, safety management culture or just another facet of human behaviour?
Join Date: May 2002
Location: MA
Posts: 300
Likes: 0
Received 0 Likes
on
0 Posts
Great post, alf! You really hit the nail on the head in many ways. We ignore, for the most part, the near accidents... we learn little from them, we pay so little attention to them. And they would have been serious, fatal accidents but for what... luck? I am so taken back to a book I first read when I was about 12 years old, Ernie Gann's Fate is the Hunter.
Oh, and after reading the Alex Patterson article on the Longbow vs the crossbow, I have finally learned the origin of the digital indicator of displeasure, giving the middle finger!
Oh, and after reading the Alex Patterson article on the Longbow vs the crossbow, I have finally learned the origin of the digital indicator of displeasure, giving the middle finger!
Join Date: Jan 2004
Location: Thailand
Posts: 6
Likes: 0
Received 0 Likes
on
0 Posts
As a SLF and long time lurker I am very hesitant to post - but here goes anyway.
Perhaps there is a problem in the thrust control mechanism that, despite the pilot retarding the TL correctly, the thrust control has stayed at the CLB level.
In post no. 1580 VAPILOT describes the control system as -
Each thrust lever is connected by a pushrod to the
input of an artificial feel unit. This unit provides friction
and the detents throughout the motion of the thrust levers.
The artificial feel unit's output shaft is connected
to the thrust control unit via a second pushrod.
Within each thrust control unit are 6 potentiometers
and 2 thrust angle resolvers.
I presume the artificial feel unit and the thrust control unit are on the same mounting.
Could this mounting have come adrift from its moorings in such a way that, as the TL is retarded the mounting is pulled (or pushed) from its position, but subsequently when the TL is advanced, the mounting is pushed (or pulled) back 'home.' Thus the second pushrod doesn't move after the time the mounting leaves its home position.
I can't recall there being any mention of what the original problem was with the thrust reverser - or when it happened. Could this have been the first time the problem occurred? Say the mounting came loose when the TL was moved from reverse idle to full reverse, and they received only idle reverse. Or if it came loose from the idle position, the reverser would not have deployed at all.
This also explains why in the last three landings there have been apparently three different ways of handling the TL, while probably the pilots followed SOPs.
One problem though. If this is the case, there would be no feedback from the artificial feel unit to the TL once the mounting has left home. Would this be noticed by the pilot? Take into account the faulty TL is being moved in unison with the good TL which is receiving feedback, and this was occurring at the busiest part of the flight.
When the PNF called "look this", was he showing the PF that the TL could be moved without resistance?
Perhaps there is a problem in the thrust control mechanism that, despite the pilot retarding the TL correctly, the thrust control has stayed at the CLB level.
In post no. 1580 VAPILOT describes the control system as -
Each thrust lever is connected by a pushrod to the
input of an artificial feel unit. This unit provides friction
and the detents throughout the motion of the thrust levers.
The artificial feel unit's output shaft is connected
to the thrust control unit via a second pushrod.
Within each thrust control unit are 6 potentiometers
and 2 thrust angle resolvers.
I presume the artificial feel unit and the thrust control unit are on the same mounting.
Could this mounting have come adrift from its moorings in such a way that, as the TL is retarded the mounting is pulled (or pushed) from its position, but subsequently when the TL is advanced, the mounting is pushed (or pulled) back 'home.' Thus the second pushrod doesn't move after the time the mounting leaves its home position.
I can't recall there being any mention of what the original problem was with the thrust reverser - or when it happened. Could this have been the first time the problem occurred? Say the mounting came loose when the TL was moved from reverse idle to full reverse, and they received only idle reverse. Or if it came loose from the idle position, the reverser would not have deployed at all.
This also explains why in the last three landings there have been apparently three different ways of handling the TL, while probably the pilots followed SOPs.
One problem though. If this is the case, there would be no feedback from the artificial feel unit to the TL once the mounting has left home. Would this be noticed by the pilot? Take into account the faulty TL is being moved in unison with the good TL which is receiving feedback, and this was occurring at the busiest part of the flight.
When the PNF called "look this", was he showing the PF that the TL could be moved without resistance?
Join Date: Jul 2007
Location: Germany
Posts: 556
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by Lemurian
1/- I believe, with more than ten years of experience of the airplane, that the non-moving throttle choice was the result of the envelope protection decision, and particularly the Alpha floor, in which an automatic application of go-around thrust, along with the reduction of the AoA happens.
A surprised crew would, in all probability, react first toward grabbing the T/Ls moving to full thrust, thus denying the safety philosophy of the system.
A surprised crew would, in all probability, react first toward grabbing the T/Ls moving to full thrust, thus denying the safety philosophy of the system.
Do you know of any statistics about how often the Alpha-Floor-Protection was activated "in anger"? I. e. to save an aircraft inadvertently manoeuvred into the near-stall region of the flight envelope?
(For those still interested in the Ford Trimotor-type set-up, this can be disabled but the Habsheim accident proves that it is not generally a good idea to do so ).
Bernd
Last edited by bsieker; 27th Aug 2007 at 08:54.
Join Date: Jun 2001
Location: East of the Sun & West of the Moon
Posts: 286
Likes: 0
Received 0 Likes
on
0 Posts
alf5071h,
Definitely some important points to consider. For discussion:
Unless we are looking at different documents there was no briefing included in the CVR Transcript. It starts 30 minutes prior to the event with the Captain's PA to the passengers. There is a 22 minute gap from 18:22:39-18:43:04, but it has to be assumed that this because there was nothing pertinent recorded in this interval. Quite possibly the briefing took place just prior to the PA, which is often the case, and was either no longer on the recording or has not been released for some reason.
The FDR data for the previous landing at Porto Allegre shows that the movement of the 2 TL's was synchronous from CLB to IDLE to REV IDLE to MAX REV and back to IDLE. I believe that it has been established that this landing was accomplished by the same crew with the other pilot handling the aircraft.
How do we know that the bells weren't rung in some quarters? Is it possible that factors other than changes to the runway surface condition were present in the other two incidents (as is the case here) and were quickly determined to have been the deciding factors in those incidents? If so a decision to continue normal operations may not have been unreasonable. How many pilot reports regarding low runway friction were received prior to the event and how were those investigated?
Well, of course there is the "sensational" aspect which attracts a great degree of attention, but the other reason why this accident is generating so many posts is the unusual amount of factual data that has been released publically in advance of the completed investigation. That amount of data is not available with respect to the other incidents so there is nothing there for qualified observers to consider. In the case of the B737 there's a picture of where the aircraft ended up, but very little information about how it actually got there.
Of course we are. Public (as in where there is the attention of the general population as opposed to just industry professionals) attention is always biased towards the tragic results of a process gone wrong and not the indicators of risk that a process is going wrong that appear before the tragic result. That is human nature, but it doesn't preclude that there may have been significant discussions occuring pre-event among the professionals involved in operations at CGH. What those discussions may have been and what conclusions may have been drawn would certainly add a great deal to the discussion here. So far though, aside from a few generally attributed "A XXX pilot said this ...", there has been no real reporting of what was happening at CGH prior to the accident.
I would agree that the focus on "the ‘bright’ or emotive aspects of automation" is for the most part a misplaced one that seems mostly to have been introduced by observers who don't have personal knowledge of the automation. How the automation works in practice for someone trained in its use versus how the automation is supposed by someone who has no experience with it in reality are two very different things, and that split is clearly shown by the difference in comments here between those who have that experience and those that don't.
Perhaps so. Each of our backgrounds biases the direction from where we perceive the greatest risk might have been. For bubbers et al it's clearly simply in flying an Airbus with non-moving thrust levers. For others it relates primarily to the runway length and condition, and some like yourself see the MEL’ed reverse and associated procedure as having a higher level of precedence in the chain of causation. My interpretation of the information available leads in the direction of the braking procedures being a key link in the risk assessment chain.
In a previous post you said:
Personally, I don't think that this case has been made as of yet. To me, the degree to which the availability of the TR's is relevant to the decision is directly related to the degree of certainty that the crew believed they had in the condition of the runway. The TR's don't factor into the aircraft's assessed stopping capability though they do provide an increased margin against limiting conditions. Suggesting that the go/no-go decision should have been made with the availibility of reverse as a primary basis of consideration would be to suggest that the current regulated operating margins are insufficient. Perhaps that is true, but if it is I think it would be a bit unfair to assess a failure of adequate judgement to the crew (as opposed to the manufacturer/regulator/operator) for not demanding a higher margin than regulations require.
To me, a key point in the land/divert judgement was the crew's assessment of the runway condition based on the available information. How often is CGH reported as "wet and slippery" and what meaning did those words have from the crew's perspective? Experience biases our judgement and a man who has done many landings at CGH, and likely received many "wet and slippery" reports there, has probably built a particular model of stopping performance expectations. We'll never know for this particular crew, but important related questions that I see are:
If the pilots had a high degree of certainty about the stopping action they expected and that that level was within the documented safe range for operating the aircraft, then I don't think the aircraft condition with respect to reverse plays much of a factor. However, if the opposite is true, that the pilots had a lowered level of confidence about the stopping action, then I would agree that the aircraft configuration with respect to reverse becomes a key consideration in the risk assessment and decision making process that took place prior to the landing.
This is, in my opinion, an critical set of questions. The answers in this case might tell us alot about the delay in the application of manual braking on landing. The basic performance data available makes it clear that landing at CGH in wet conditions is an operation that approaches the limits of the aircraft's performance, and the pilot's decision to go below the G/S to achieve an early touchdown supports that he was aware of that fact. So, why then did he consider it acceptable to wait for confirmation of autobraking as opposed to considering it neccessary to apply manual braking right from the moment of touchdown?
I don't mean this to imply criticism of the pilot specifically, it may have more to do with manufacturer or company training or standard procedures, but if there's a clear failure of risk assessment evident in the information so far available it is the failure to appreciate the importance of ensuring (not assuming) immediate braking on landing when operating into a runway which is close to the limiting conditions of the day.
Researching what printed guidance there was on the subject I came up with the following from the Airbus FCTM (02.160 P6-8):
So, questions from this might be:
ELAC
Definitely some important points to consider. For discussion:
Although the lack of reverse was in the briefing, the exact procedure was not discussed which deprived the handling pilot opportunity to visualise his intended actions (recall and refresh from memory), and for the monitoring pilot to both understand the ‘plan’ (what he would be monitoring) and an opportunity to interject if the briefed procedure was incorrect.
The possibility that neither crew member knew of the revised procedure remains open, but they had landed in this configuration previously – what procedure was used then?
Post#1893 reports an earlier A320 incident; considering the previous ATR incident and an earlier excursion with a 737, then the indications of this operation was one of high risk. ...
So why didn’t the 737 overrun (or previous ATR, F100 incidents) ring the safety alarm bells, trigger a risk assessment and the reconsideration of operations during the temporary conditions affecting the runway?
So why didn’t the 737 overrun (or previous ATR, F100 incidents) ring the safety alarm bells, trigger a risk assessment and the reconsideration of operations during the temporary conditions affecting the runway?
Why did the TAM overrun generate 1900+ PPrune posts vs 11 for the 737?
Are we misjudging the important aspects of safety, being biased by fatalities, or incorrectly focussing on the ‘bright’ or emotive aspects of automation?
I would agree that the focus on "the ‘bright’ or emotive aspects of automation" is for the most part a misplaced one that seems mostly to have been introduced by observers who don't have personal knowledge of the automation. How the automation works in practice for someone trained in its use versus how the automation is supposed by someone who has no experience with it in reality are two very different things, and that split is clearly shown by the difference in comments here between those who have that experience and those that don't.
The risk assessment reflected in this thread appears to be biased, if true then is this due to a failure in our beliefs, knowledge, training, safety management culture or just another facet of human behaviour?
In a previous post you said:
With hindsight the aircraft should not have made the approach due the combination of runway / airport conditions and aircraft configuration. Thus a conclusion could be that there was a failure in risk assessment.
To me, a key point in the land/divert judgement was the crew's assessment of the runway condition based on the available information. How often is CGH reported as "wet and slippery" and what meaning did those words have from the crew's perspective? Experience biases our judgement and a man who has done many landings at CGH, and likely received many "wet and slippery" reports there, has probably built a particular model of stopping performance expectations. We'll never know for this particular crew, but important related questions that I see are:
- What level of degradation in performance do pilots at CGH practically associate with a "wet and slippery" report and how does that align with the reference values of "wet" in use to determine the aircraft's capability? If they typically associate this with lower performance than "wet" then there's a clear indication of a risk not adequately assessed by the operator as well as the crews.
- What was the actual friction coefficient at the time and how well did it align with the "wet and slippery" report issued by the tower? Does "wet and slippery" have the same meaning for the issuers of the report as it does for the recipients?
- How much effect did the resurfacing work have on braking conditions and how well was this reflected in modifications to braking action conditions reported by the tower or assessed by pilots?
- Overall, what level of confidence did the pilots have in correlating runway condition reported to actual braking action experienced?
If the pilots had a high degree of certainty about the stopping action they expected and that that level was within the documented safe range for operating the aircraft, then I don't think the aircraft condition with respect to reverse plays much of a factor. However, if the opposite is true, that the pilots had a lowered level of confidence about the stopping action, then I would agree that the aircraft configuration with respect to reverse becomes a key consideration in the risk assessment and decision making process that took place prior to the landing.
Much has been said about landing distances, but how often do crews assess their landings against the requirements? Do crews routinely assess if the aircraft was capable of stopping within the safety margins provided for a limiting runway? Do crews check what % of max landing weight they are at, or how much additional runway they have/have not for a normal landing? Most landings are made on non limiting runways thus crews have few references as to how close they were to the required limiting performance, particularly in less than ideal conditions.
I don't mean this to imply criticism of the pilot specifically, it may have more to do with manufacturer or company training or standard procedures, but if there's a clear failure of risk assessment evident in the information so far available it is the failure to appreciate the importance of ensuring (not assuming) immediate braking on landing when operating into a runway which is close to the limiting conditions of the day.
Researching what printed guidance there was on the subject I came up with the following from the Airbus FCTM (02.160 P6-8):
BRAKES
The use of auto brake versus pedal braking should observe the following guidelines:
The use of auto brake versus pedal braking should observe the following guidelines:
- The use of A/BRAKE is usually preferable because it minimizes the number of application of brake and thus reduces brake wear. Additionally, the A/BRAKE provides a symmetrical brake pressure application which ensures an equal braking effect on both main landing gear wheels on wet or evenly contaminated runway. More particularly, the A/BRAKE is recommended on short, wet, contaminated runway, in poor visibility conditions and in Auto land. The use of LO auto brake should be preferred on long and dry runways whereas the use of MED auto brake should be preferred for short or contaminated runways. The use of MAX auto brake is not recommended.
- On very short runways, the use of pedal braking is to be envisaged since the pilot may apply full pedal braking with no delay after touch down.
- How much of this advice makes into line training?
- What differentiates a very short runway from a short runway?
- Did TAM make this distinction with regard to CGH?
- What if any training occurs to help aid the pilot in making the distinction when conditions vary?
ELAC
Per Ardua ad Astraeus
Join Date: Mar 2000
Location: UK
Posts: 18,579
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by ELAC
I think it would be a bit unfair to assess a failure of adequate judgement to the crew (as opposed to the manufacturer/regulator/operator) for not demanding a higher margin than regulations require.
I have to say that like others I would probably not have tried to land there that evening in that aircraft.
An interesting point arises from the AB FCTM: I was always taught (Boeing) to use autobrake when conditions might be marginal (since application of 'manual' braking can be delayed sometimes if you finish up doing a 'soft-shoe-shuffle' on the rudder pedals) and then to apply the required foot pressure. Has this advice now dropped out of the frame?
Join Date: Aug 2007
Location: The Netherlands
Age: 67
Posts: 288
Likes: 0
Received 0 Likes
on
0 Posts
BRAKING and READING
The question of BOAC in post 1916 is interesting because it shows how difficult communication really is at all levels.
The post of ELAC, that BOAC refers to, mentions that on very short runways, manual braking is "envisaged". The question of BOAC seems to imply that this term means that autobraking is not to be used.
NOT SO! There is every reason to set the heaviest practical autobrake level (but Airbus states that MAX should not be used for landing), but then to try to manually win from the autobrakesystem by applying brakes quicker and harder. The "footshuffle" that BOAC mentions, probably leads to the practical result that autobrake applies brakes quicker, but pilot then counters with heavier brake pressure than autobrake would have given (don't managers call that a win-win situation?)
The reading but perhaps not fully understanding of what is written can be observed more often in the postings - I can recall from a long way back that a B-757 driver quoted his FCOM as stating the thrust leverS have to be in idle before the reverse leverS can be raised. He did not quote however a paragraph from a few pages earlier stating that each engine has its' INDIVIDUAL CONTROL (= thrust lever) on the flight deck. (individual means independant of each other).
The post of ELAC, that BOAC refers to, mentions that on very short runways, manual braking is "envisaged". The question of BOAC seems to imply that this term means that autobraking is not to be used.
NOT SO! There is every reason to set the heaviest practical autobrake level (but Airbus states that MAX should not be used for landing), but then to try to manually win from the autobrakesystem by applying brakes quicker and harder. The "footshuffle" that BOAC mentions, probably leads to the practical result that autobrake applies brakes quicker, but pilot then counters with heavier brake pressure than autobrake would have given (don't managers call that a win-win situation?)
The reading but perhaps not fully understanding of what is written can be observed more often in the postings - I can recall from a long way back that a B-757 driver quoted his FCOM as stating the thrust leverS have to be in idle before the reverse leverS can be raised. He did not quote however a paragraph from a few pages earlier stating that each engine has its' INDIVIDUAL CONTROL (= thrust lever) on the flight deck. (individual means independant of each other).
Per Ardua ad Astraeus
Join Date: Mar 2000
Location: UK
Posts: 18,579
Likes: 0
Received 0 Likes
on
0 Posts
It certainly does not read that way. I would have preferred to see clear emphasis on using A/Brake and then, asap, applying 'manual' brakes. What is actually taught by AB?
Join Date: Jun 2001
Location: East of the Sun & West of the Moon
Posts: 286
Likes: 0
Received 0 Likes
on
0 Posts
BOAC,
I think there are good questions to ask about the characteristics of newly paved surfaces. If there are differences that occur in the "curing" process then they should be identified and accounted for in performance planning. I suspect one of the problems would be that different processes in different places will have different results, so a rule based response might not be as good as a test or observation based response.
There is also the matter of the number of ungrooved runways that still exist and the higher risk they impose on operations. Why do regulators allow that risk to continue when there must be some practical grooving methods that can be applied even to older and sub-standard runway surfaces? Your concerns regarding hydroplaning are most particularly apt in respect of the combination of non-grooved, questionably crowned runways in areas of poor drainage, and there are quite a few of those still out there.
Nor likely would I have, but I do respect that specific training and experience with that operation would make me approach the judgement differently. The answer for me might have remained the same, but possibly not.
No, I don't think so. The guidance for the planned use of autobrake in most situations where significant braking is required is sensible since it provides a quicker and more consistent start to braking than the pilot is likely to achieve and can help with directional control issues when braking coefficients are low. I think that the last bit about the use of manual braking on very short runways is meant to cater to instances when you are operating at or near the limits of the aircraft's performance where there may not be a sufficient margin between the required and the available distances to permit a failure of the automated system to occur, be recognized and be responded to safely. Hence the recommendation to plan manual braking which is consistent with what is written a bit later and which applies to all of us whether Airbus, Boeing or of any other stripe:
Personally I take a belt and suspenders approach. If the approach is a difficult one the manual braking can get delayed so I'd want the autobrake backing me up in case my planned manual braking was delayed. For a situation similar to this I would have had the autobrake armed at medium, but intended to use it only as a backup to manual braking commencing at touchdown. If you look at the FDR data for the previous landing at CGH you will see that this is how the pilot who did that landing approached the situation as well. Why the pilot in this case didn't choose the same approach is, to me, a critical question.
ELAC
I support the call for all new runway surfaces to be 'reclassified' when wet particlarly until grooving is complete.
There is also the matter of the number of ungrooved runways that still exist and the higher risk they impose on operations. Why do regulators allow that risk to continue when there must be some practical grooving methods that can be applied even to older and sub-standard runway surfaces? Your concerns regarding hydroplaning are most particularly apt in respect of the combination of non-grooved, questionably crowned runways in areas of poor drainage, and there are quite a few of those still out there.
I have to say that like others I would probably not have tried to land there that evening in that aircraft.
An interesting point arises from the AB FCTM: I was always taught (Boeing) to use autobrake when conditions might be marginal (since application of 'manual' braking can be delayed sometimes if you finish up doing a 'soft-shoe-shuffle' on the rudder pedals) and then to apply the required foot pressure. Has this advice now dropped out of the frame?
Auto-brake does not relieve the pilot of the responsibility of achieving a safe stop within the available runway length.
ELAC
Join Date: Jul 2007
Location: Germany
Posts: 556
Likes: 0
Received 0 Likes
on
0 Posts
The post of ELAC, that BOAC refers to, mentions that on very short runways, manual braking is "envisaged". The question of BOAC seems to imply that this term means that autobraking is not to be used.
NOT SO! There is every reason to set the heaviest practical autobrake level (but Airbus states that MAX should not be used for landing), but then to try to manually win from the autobrakesystem by applying brakes quicker and harder. The "footshuffle" that BOAC mentions, probably leads to the practical result that autobrake applies brakes quicker, but pilot then counters with heavier brake pressure than autobrake would have given (don't managers call that a win-win situation?)
NOT SO! There is every reason to set the heaviest practical autobrake level (but Airbus states that MAX should not be used for landing), but then to try to manually win from the autobrakesystem by applying brakes quicker and harder. The "footshuffle" that BOAC mentions, probably leads to the practical result that autobrake applies brakes quicker, but pilot then counters with heavier brake pressure than autobrake would have given (don't managers call that a win-win situation?)
What can make a (possibly crucial) difference is that manual braking can be commenced with maximum pressure (limited by anti-skid) as soon as MLG touches down, before the nosewheel touches down. (This precedure is explicitly allowed, discouraged only for comfort reasons).
(Leaving aside possible foot shuffle; if necessary the PNF could prepare for manual braking while the PF is keeping the A/C straight with the rudder. Forgive me if this is so far outside SOPs as to be not considered.)
Autobrake MED has a 2 second delay (usually enough for a quick derotation), and LO has a 4 second delay (allowing for a slower, smoother derotation) after MLG touchdown; both apply pressure "progressively", which I read as slowly increasing.
I also understand "use of manual brake should be envisaged" as "watch autobrake closely and use manual braking as soon as possible when necessary". Except in the case of an autobrake failure I don't see the benefit of this course of action on slippery surfaces, since it will not give higher deceleration (assuming the friction coefficient tlimits deceleration to less than 3.0 m/s^2, and autobrake MED selected).
Bernd
Last edited by bsieker; 27th Aug 2007 at 13:05. Reason: Spelling
Paxing All Over The World
(non-pilot speaking) Yesterday I has a most interesting example of the way in which human audio processing is inhibited during times of sudden crisis.
In the car approaching a complicated, but to me well known, traffic intersection. I was listening to a spoken word radio programme and was following the conversation. As I moved into the junction, a car on my left made an erratic movement and threatened to enter the road space that I was driving into. At the same moment, I saw a Police car parked on the far side with it's blue lights on and I had to assess what the problem was and how it would affect me, as well as avoiding being hit by the car on my left.
Fortunately, all went well and I exited from the junction without incident. This was not a crisis, just a momentary every day traffic problem but, as I drove away, I realised that I had 'lost' about 7 seconds of the radio programme as my brain focused on the problem.
Professional pilots are, of course, trained rigorously to be able to maintain sensory input but it was a fascinating example of how easily the hearing function is 'downgraded' by the brain. Which led me to think that enhanced audio prompting as suggested in this thread, "Retard Two, Retard Two" may not have the desired effect. Of course, that is no reason not to implement it as we cannot know how we are going to react when faced with 'the real thing'.
In the car approaching a complicated, but to me well known, traffic intersection. I was listening to a spoken word radio programme and was following the conversation. As I moved into the junction, a car on my left made an erratic movement and threatened to enter the road space that I was driving into. At the same moment, I saw a Police car parked on the far side with it's blue lights on and I had to assess what the problem was and how it would affect me, as well as avoiding being hit by the car on my left.
Fortunately, all went well and I exited from the junction without incident. This was not a crisis, just a momentary every day traffic problem but, as I drove away, I realised that I had 'lost' about 7 seconds of the radio programme as my brain focused on the problem.
Professional pilots are, of course, trained rigorously to be able to maintain sensory input but it was a fascinating example of how easily the hearing function is 'downgraded' by the brain. Which led me to think that enhanced audio prompting as suggested in this thread, "Retard Two, Retard Two" may not have the desired effect. Of course, that is no reason not to implement it as we cannot know how we are going to react when faced with 'the real thing'.
Sun worshipper
Join Date: Dec 2001
Location: Paris
Posts: 494
Likes: 0
Received 0 Likes
on
0 Posts
TOGA lock
the locked TOGA thrust ("TOGA LK" FMA display after Alpha floor condition is resolved), unlike other thrust-lock situations, cannot be cancelled be simply moving the thrust levers: autothrust has to be disconnected explicitly. (I could not find whether instinctive disconnect and/or moving levers to idle will suffice -the latter might be impossible, since Alpha-floor protection will activate even with levers in idle-, or if disarming it with the A/THR pushbutton is required.)
ex-Tanker
Join Date: Apr 2000
Location: Luton Beds UK
Posts: 907
Likes: 0
Received 0 Likes
on
0 Posts
Cars and planes...
Pax Boy,
A nice analogy, which just shows how the brain prioritises events.
However the likely scenarios on the road are myriad - on a sterile runway much less so - and those that do exist are often trained for in detail.
Also there are two pilots but only one "pilot" in your car, so the back up system is not in place (unless your mother in law is in the back seat...)
Here are two professionals, with an out of the ordinary situation, who have to assess the situation on the basis of trained emergencies and system knowledge and come up with a procedure, possibly also based on trained procedures to deal with it.
If they had managed it, this thread would not be here. As they didn't, it is. It is a fine line...
A nice analogy, which just shows how the brain prioritises events.
However the likely scenarios on the road are myriad - on a sterile runway much less so - and those that do exist are often trained for in detail.
Also there are two pilots but only one "pilot" in your car, so the back up system is not in place (unless your mother in law is in the back seat...)
Here are two professionals, with an out of the ordinary situation, who have to assess the situation on the basis of trained emergencies and system knowledge and come up with a procedure, possibly also based on trained procedures to deal with it.
If they had managed it, this thread would not be here. As they didn't, it is. It is a fine line...
Last edited by Few Cloudy; 27th Aug 2007 at 17:02.
Join Date: May 2000
Location: Glorious West Sussex
Age: 76
Posts: 1,020
Likes: 0
Received 0 Likes
on
0 Posts
Lemurian
Not true. You use the A/THR disconnect pushbutton on the thrust levers.
TP
The only way of exiting TOGA LK is by pressing the A/THR switchlight.
TP
Join Date: Nov 2004
Location: Dubai
Posts: 81
Likes: 0
Received 0 Likes
on
0 Posts
Good Reason
Looks like some pretty good info here. I tend to agree.
http://brazil.suite101.com/article.c..._investigation
The data shows important information that will most likely be listed as a primary contributor to the cause of the accident.
* The aircraft failed to decelerate due to failure of the brakes and ground spoilers to actuate early in the landing roll. This was caused by failure to retard the #2 engine to idle thrust.
http://brazil.suite101.com/article.c..._investigation
The data shows important information that will most likely be listed as a primary contributor to the cause of the accident.
* The aircraft failed to decelerate due to failure of the brakes and ground spoilers to actuate early in the landing roll. This was caused by failure to retard the #2 engine to idle thrust.
Join Date: Sep 2000
Location: Bielefeld, Germany
Posts: 955
Likes: 0
Received 0 Likes
on
0 Posts
I'm having a little bit of a problem; maybe someone can help. The TAM president told Congress recently that TAM was going to implement the latest SB from Airbus, which includes a warning about mismatched thrust levers. The operation of the warning was published by, for example, Veja about a week ago. The SB is supposedly 31-1267, issued 13 November 2006. It replaces FWC standard H2-F2 with standard H2-F3.
Revision 2 of SB 21-1267 is dated 16 July 2007, the day before the Congonhas crash. But I cannot find anything about a warning system for thrust-lever mismatch in the description. Can anybody who *knows* please say whether it is there or not in 31-1267, or Revision 1 or Revision 2?
If not, is there by any chance a Revision 3 which includes it? With which date?
PBL
Revision 2 of SB 21-1267 is dated 16 July 2007, the day before the Congonhas crash. But I cannot find anything about a warning system for thrust-lever mismatch in the description. Can anybody who *knows* please say whether it is there or not in 31-1267, or Revision 1 or Revision 2?
If not, is there by any chance a Revision 3 which includes it? With which date?
PBL
Join Date: Jul 2007
Location: Brasilia - Brazil
Posts: 10
Likes: 0
Received 0 Likes
on
0 Posts
PBL - Airbus Service Bulletin
PBL- TAM distributed Rev 2 to the press, to "prove" that they were not to blame for not "knowing" about the new TL ABV IDLE alert. That is because, as you noted, it is not explicit in Rev 2, which is classified "desirable". I don´t know if it would be in the original SB (NOV 13 06) or first revision (MAY 21 07), but i don´t think it is very likely to be explicit anywhere. This is why:
The alert was announced by Airbus after the Taiwan accident and to be issued "soon" in the H2F3 standard. But according to Yannick Malinge, certification authorities did not see the alert as efficient and practical, in terms of creating situational awareness for the pilot in the split second scenario of TL ABV IDLE.
Please let me know if you advance on this.
The alert was announced by Airbus after the Taiwan accident and to be issued "soon" in the H2F3 standard. But according to Yannick Malinge, certification authorities did not see the alert as efficient and practical, in terms of creating situational awareness for the pilot in the split second scenario of TL ABV IDLE.
Please let me know if you advance on this.
I support PPRuNe
Join Date: Jul 2007
Location: Belo Horizonte, Brazil
Posts: 162
Likes: 0
Received 0 Likes
on
0 Posts
Software
The Airbus software that TAM is going to buy and install in all A320s is called FW3.
Excuse me for saying this, since I am not a commercial pilot. Small fish
that never got there. But I did fly Cherokees and before Piper Tripacers.
Now the question: this is the third similar accident. Do we really think they are only human errors?...
Excuse me for saying this, since I am not a commercial pilot. Small fish
that never got there. But I did fly Cherokees and before Piper Tripacers.
Now the question: this is the third similar accident. Do we really think they are only human errors?...
Last edited by marciovp; 27th Aug 2007 at 23:13. Reason: Adding something