TAM A320 crash at Congonhas, Brazil

[ChristiaanJ]

SyEng,

I've had enough of re-iterating the same old points and I concede that I'll never get through to those who have already made their minds up, so I'll shut up now.

We must be a very small minority having been through all the 2100 posts so far. So yes, the same old points have been re-iterated, but let's try and give a hand to the late-comers. They also want to learn.

EMIT,

Next point is, as a pilot, I think that the most valuable point to ponder is, the question how or why did the PF leave the T/L #2 in CLB detent?

If you start looking back through the earlier posts, you will find mostly two answers.

1) Somehow, somewhere, landing on a short slippery runway, with one TR locked out, with none-to-clear SOPs about how to handle TL and TR in that case, with a vague memory of having to leave the TL concerned in idle, not reverse idle, etc. etc. the PF did not move the #2 TL but left it in CLB detent.
The ensuing chaos was not something the average human mind could sort out in the 90 seconds remaining.
Some of the posts on that subject are really worth reading.

2) The pilot pulled both TLs to idle, but there was a mechanical or electrical failure, so the engine controls still saw "CLB detent".

Personally, I've seen so many well-reasoned posts on the subject, that I tend towards 1). "Pilot error"? Yes. But that "pilot error" was only the end of a long chain of "causal factors", that should be addressed.

2) ? As an engineer, I find it improbable at just that moment. But, again as an engineer, I will not discard that answer until there is evidence to the contrary.

[marciovp]

ANAC´s Normative Instruction IS 121-189

Things get a little complicated. A Federal Judge had issued an order to close Congonhas Airport. Then ANAC (National Agency Civil Aviation) published in their website the "Instrução Normativa IS-121-189" stating that for an airplane to land in Congonhas both reversers should be on and working. Gilberto Schittini who elaborated the IS said today that it was in force. This was shown to the judge who after reading it allowed Congonhas do open. Then a director from ANAC Denise (she asked to leave) said that the IS was not enforced and was published in the site of ANAC by mistake. That it was just an internal discussion not to be promulgated as valid. Not so, said Gilberto Schittini, saying that he cried when he realized that if TAM followed his IS-121-189 the disaster would not happen. TAM said that it followed the Airbus directives not ANAC´s...

Here is the news (portuguese-brazilian):
http://si.knowtec.com/scripts-si/Mos...ata=2007-09-07

In case you all want to know, I am not a lawyer and I have no agenda. I just love aviation. I am a psychiatrist/psychoanalyst who used to fly Piper Tripacers and Cherokees (ah, also a Cessna 150). In my work with patients I prepare them to "fly solo" in this world...

[Lemurian]

the WBA graph

bsieker,
There are a few points that seem to be absent in the graph :

1. Between 11 and 12, there is no *No Decel* call out, whether it is in the SOPs or not, that call, in the airlines where it is SOP is a trigger for manual brake application,
2. Looking at the rudder displacement print-out, it appears that there was some rather drastic application of rudder pedal, hence the assumption that, combined with 26 -*persistent significant forward thrust*- and 28 -*lower friction coefficient* -, there was some directional control difficulties which would have participated in 25 -*lower than expected wheel brake deceleration*-, or even 20 -*wheel brake application is delayed*-.
3. I think that the "flatness" of the captain's 'stick inputs cannot be discarded, especially when we observe that quite early the F/O flight controls seem to be very active and that he is the one going aggressively with the braking.There is, from the FDR a glaring takeover by the F/O.
   (I'm going to hate myself for this but it looks as if F/C suffered some incapacitation of some sort , whether mental -approach / landing /weather stress combined with a rapidly deteriorating situation -, psychological - bowing to the F/O' apparently strong personality - or plain physical ).

Sorry, I'd have preffered someone to pick on my earlier hints but nobody seemed interested.
Need to rest now.
Regards.

[Dani]

Thank you to the two Engineers (SyEng and ChristiaanJ) for repeating the technical reasoning. I'm sad that SyEng won't take part anymore because he showed the way of thinking with much more patience than I could.

For our Brazilian friends, who joined us later, two more points have to be added:

1. Technical failure:

If there was a broken TL or any associated system there would have been a failure/warning produced by the FWC/ECAM. The system is so heavily electronified that several sensors watch each other, and if one sensor fails you also get a warning. This has been explained before but I couldn't find it anymore. I'm aware that we don't possess the FDR data from the ECAM but it can be assumed with high certainty that if there had been such failures, the Brazilian authorities would be the first to publish it, and Airbus would have also given out bulletins to their operators, maintenance personal and pilots.


2. Human aspect:

If there would have been a failure in the TL, its associated system, in the EEC, the FADEC, the trust revers system or any other relevant system, the pilots would have reacted differently. In case their intention was to stop (as they were) and a TL failure occurs, they would cut a trusting engine, i.e. put Master Switch 2 to off.
If their intention was not to cut engine 2, go around, they would have to put both TL to TOGA, would have gone around and problem would also be solved. Remember that with only minimal higher speed than they had at the end of the runway, they could have attempted a GA.

These two aspects lead most of us to believe that we can falsify the other reasons just brought up again by our Brazilian friends and the Brazilian Parliament committee.

[Sorry for my convinced way of arguing now and in all my previous posts. It doesn't mean that I have evidence but that I follow the most likely causes and put them together. If I use the words certainty and likelihood, it doesn't imply that I have the absolute solution.]

Can we finally agree with that and come back to a more needed discussion about what to do to avoid further accidents like these?

Dani

[bubbers44]

Dani, On a short slick runway as soon as you touch down you will be in reverse thrust and the go around option is not recommended. A system failure, broken linkage is not something that can be easily detected by electronic detection so probably doesn't exist. If they brought both TL's to idle but the computer only sensed #1 at idle because of a linkage failure or electronic failure they would have little time to sort out the problem and shut down the #2 engine while sliding down the runway with no brakes because for some reason they didn't use manual brakes. Without ground spoilers and auto brakes they were in a desperate situation but if they didn't push on the brake pedals why would they shut down an engine to help their situation? 11 seconds is a very long time to not try to save yourself by simply pushing on the brake pedals. Only when manual braking is applied would the thought of shutting down an out of control engine enter your mind.

[bsieker]

Originally Posted by flyingnewbie10

I will dare to post a preliminary comment about your why-because graph. My apologies If I say any nonsense:

Thank you very much for your comments.

1 - Factor 11 (assumption) could well be the one you pointed out (F/C did not expect autobrake not to operate) to explain F/C not commencing "Loss of Braking" procedure immediatelly. But if "Loss of Braking" implies using full manual braking (is it ?)

As much as you deem necessary. Since it is often an emergency situation, I would guess that it usually implies full braking. (On less than optimal surface conditions brake performance will be limited by anti-skid anyway.)

I suppose it could also be explained by the fact that the crew at least thought that the runway was slippery and did not start using braking immediatelly to avoid an hydroplanning as the speed was still high;

I don't think so. As someone has pointed out, hydroplaning is independent of braking, it happens even with spinning wheels. (In driver-training one common exercise is to accelerate in (low) standing water and experience the onset of loss of control (steering) that happens at hydroplaning. Don't try this on public roads!) For all we know anti-skid was operative, so would prevent wheel-locking. (I have to admit I don't know if or how well it works during hydroplaning.)

The strongest argument, though, is that they had selected autobrake MED, which would commence braking 2s after MLG touchdown, even though they perhaps suspected the runway to be slippery and maybe anticipated some degree of hydroplaning.

I don't think it makes any sense to delay braking because one anticipates hydroplaning.

2 - Is there a way to have a more detailed description of factor 18 (Thrust Lock after A/THR disconnected) just to contemplate the fact that it worked exactly as designed and the "locked" thrust was within the range of the right TLA reading ?;

Since it worked as designed, I don't think there is a need for that. I may add an annotation that the locked thrust was well below the maximum allowed by A/THR operation.

3 - Does the graph accept multiple assumptions ? Could Factors 36 and 42 have parallel hypothesis ?

Not normally. The usualy way to deal with differing possible explanations for one event is to create a set of subgraphs for the event in question.

I have included the one (of many) hypothesis that I consider the most likely. Others may disagree, which is why I have marked the nodes as assumptions.

Both (6) and (36) have alternative explanations, and, of course, (42) also requires an explanation. Be it crew action, or a mechanical problem impeding free movement of the levers. After the final report is released, this may be amended.

The stopping rule in WBA, i. e. when to leave nodes as leaves, is variable and depends on the intended scope, the available information, and other factors. I have decided in this case that I have too little information to decide why (42) might have been the case.


Bernd

[Jorge_Vilarrubi]

bubbers44 said:
"If they brought both TL's to idle but the computer only sensed #1 at idle because of a linkage failure or electronic failure they would have little time to sort out the problem and shut down the #2 engine"

If there is a hardware failure in the TLs linkage and the computer senses Eng. #2 at CLB, let's suppose the pilots become aware of the failure and shut eng#2 down, would this action lead to Spoilers Deployment?

I apologize for my total ignorance on flying machines, I'm just a computer experienced guy.

Jorge.

[bsieker]

If there would have been a failure in the TL, its associated system, in the EEC, the FADEC, the trust revers system or any other relevant system, the pilots would have reacted differently. In case their intention was to stop (as they were) and a TL failure occurs, they would cut a trusting engine, i.e. put Master Switch 2 to off.

In case of a detected problem with the thrust levers, the engine would have been put to idle anyway, if on the ground or if in flight with slats extended, and if not during take-off/go-around (iirc FLEX or TOGA will be maintained in case of TL fault, since these settings are only used if very high thrust is crucial ...)

I'm not arguing that I believe there was an undetected fault, I also think that possibility is very remote, but my intention with making my analysis public is to have a common ground, which all can agree to, and go on from there, without having to explain everything over again.

These two aspects lead most of us to believe that we can falsify the other reasons just brought up again by our Brazilian friends and the Brazilian Parliament committee.

I mostly agree with you, but falsify is too strong a word, that would require positive evidence, that nothing was wrong mechanically, which we do not have yet.

Can we finally agree with that and come back to a more needed discussion about what to do to avoid further accidents like these?

It may be a good starting point if we could agree to the Why-Because-Graph, or if someone does not agree, modify it such that all interested parties agree that this is what we know, and other aspects are some of the most likely hypotheses.

I hope that this will give a clear overview, and eliminate a lot of questions and repetitive back-and forth on this thread.


Bernd

[bsieker]

Lemurian,

thanks a lot for your feedback.

Between 11 and 12, there is no *No Decel* call out, whether it is in the SOPs or not, that call, in the airlines where it is SOP is a trigger for manual brake application,

There are some guidelines on the incorporation of so-called "un-events" in a Why-Because Graph. It requires that the missed event is prescribed in regulations/laws, is a standard operating procedure, or at least common practice. it is not clear that this was the case in TAM operations. I may add it as an assumption, though, togehter with the missing "DECEL" light, in the same way as the missing Spoilers-indication.

Looking at the rudder displacement print-out, it appears that there was some rather drastic application of rudder pedal, hence the assumption that, combined with 26 -*persistent significant forward thrust*- and 28 -*lower friction coefficient* -, there was some directional control difficulties which would have participated in 25 -*lower than expected wheel brake deceleration*-, or even 20 -*wheel brake application is delayed*-.

Very interesting point.

Directional stability issues caused by asymmetric thrust are not in the graph, but may have played a role in brake application delay. Maybe I should add this as assumptions, together with a node about thrust asymmetry (having 26 (modified to read "... on engine #2") and 39 (or an effect of 39: "Reverse thrust on engine #1") as causal factors.)

I think that the "flatness" of the captain's 'stick inputs cannot be discarded, especially when we observe that quite early the F/O flight controls seem to be very active and that he is the one going aggressively with the braking.There is, from the FDR a glaring takeover by the F/O.

Yes, but this is most likely not a causal factor in this accident, although very interesting to note in itself, and will be subject of investigation into training procedures, etc. at TAM.

I think we cannot say who made the brake pedal inputs, and L and R here does not refer to the Captain's and F/O's pedals, but left MLG and right MLG brakes.

Sorry, I'd have preffered someone to pick on my earlier hints but nobody seemed interested.

I'm sorry, I must have missed that. Which post are you referring to?


Bernd

[Dani]

Originally posted byBsieker:
In case of a detected problem with the thrust levers, the engine would have been put to idle anyway

Bernd, I agree with you completly. I just mentioned this very unlikely cause for our Brazilian friends, who still believe that there is a great likelyhood in the scenario of the pilots fighting with TL 2. If there had been a problem in TL 2, they mostly likely wouldn't have left it in CLB. And if it had been stuck in CLB they would have simply switched it off. There was enough time.

The same I have to answer to bubber44. I do not think that GA would have been a very good solution after TR 1 on, but I add it to the scenario to show the unlikeliness. I was critizised for saying "you are not thinking logically". Our engineers repeated all technical backgrounds, I added the procedural aspects from a pilot's point of view. So we have brought up all scenarios and can assume all theirs probabilities.

Ergo there is only one reasonable answer what happened, and this is: They left it in CLB - initially most probably intentionally.

[slip and turn]

Bernd
Your continued work is I am sure extremely well regarded and much appreciated. It is very heartening to see esteemed members and indeed a broad spectrum of the PPRuNE community responding to excellent chairmanship, summation and guidance from PBL and yourself.

One point about hydroplaning/aquaplaning, if I may - I am not up with the discussion enough to understand the full significance of it now, but I hesitate to accept that the "function of the square of tyre pressure only" theory was as well known/accepted in practice as it has become with recent hindsight.

I learned the 9 x version in ATPL theory I think, but it wasn't dwelled upon in class or study notes. You really have to be a good physicist to fully understand why it is so I think. So, at least in ATPL theory, this 'phenomena' was almost treated as just one of those interesting things worth an extra mark or two. The only consequence of failing to 'know' was the loss of a mark or two. As a piece of theory, it certainly didn't receive the same attention as the speed of sound being a function of temperature only, for example.

As I said, I am however no expert, so I don't know if type-rated pilots are expected to be much more aware of consequences of the theory than I was.

So I wonder if it might still be fair to say that any hesitation in braking was a natural reaction to the knowledge couplet of a reported slippery runway and any 'feeling' after touchdown that indeed it was so.

Certainly until reading the thread, and despite being taught enough about the tyre pressure angle to answer a simple exam question correctly, I would have been one who was tempted to stay off the brakes at higher speeds in the (false) assumption that I was improving my chances of a controlled stop by allowing the one reverser to do the lion's share of the initial deceleration work first. It's moot if the brakes aren't effective anyway of course, but might explain any hesitation.

My apologies if this is too simplistic to be useful.

[bsieker]

S&T,

thank you for your kind words.

(I don't know about chairmanship and guidance, I only try to figure out facts, and enjoy much of the very contentful discussion in this thread. We also found it useful to provide a concise summation of the known (and some speculated) facts and causal relationships in this accident with the help of a WB-Graph.)

So I wonder if it might still be fair to say that any hesitation in braking was a natural reaction to the knowledge couplet of a reported slippery runway and any 'feeling' after touchdown that indeed it was so.

I think the most important fact why we can dispel this theory, is that the pilots selected autobrake MED, which would have started applying brake pressure two seconds after being triggered.

If they had envisaged careful or delayed braking to avoid hydroplaning and/or its consequences (brake asymmetry comes to mind), they would have opted for manual braking from the start.


Bernd

[Rob21]

Please, correct me if I'm wrong.

1- From the "spoiler nada" call to manual brakes application five seconds went by, not ten. Why apply manual brakes before the spoiler status call?

2- The pilots "cycled" the ground spoilers armed switch almost at the same time they started applying manual brakes. This is probably because they knew braking would not be effective with no ground spoilers.

3- Autobrakes at medium is the correct (or recommended) selection for slippery runway (I learned this here).

[Lemurian]

of directional problems

Bernd,
Looking at the FDR print-out, between time tags 18:48:30 and :47, there are two very definite instances of a combination of

• an application of right *almost* full rudder
• an application of *almost* full right brake pedal application
• a release of left pedal brake

The pilot was perfectly capable of maintaining max braking on both pedals outside these instances, and others that are less obvious,considering the *apparent 1°/second sampling rate.
The only conclusion is that these instances indicate attempts -successful - at using differential braking for directional control, which seems to confirm the slipperiness of the runway (I still haven't given-up on the presence of aquaplaning ).

Directional stability issues caused by asymmetric thrust are not in the graph,

It seems that the general application of right rudder is another indication.

There is, from the FDR a glaring takeover by the F/O.
Yes, but this is most likely not a causal factor in this accident, although very interesting to note in itself, and will be subject of investigation into training procedures, etc. at TAM.

Can't it be also a factor in the delayed application of pedal brakes ? The time tags for stick inputs and braking seemed to indicate that possibility.

we cannot say who made the brake pedal inputs, and L and R here does not refer to the Captain's and F/O's pedals, but left MLG and right MLG brakes.

Yes. I've had this idea about F/O taking over so strongly and for so long that I overlooked this fact. Thanks, and apologies .

I'm sorry, I must have missed that. Which post are you referring to?

I started as early as the 10th of august : See posts 1410, 1508, 1525.
Have to go now, but I submit this document to your perusal and study, as it covers most of the oPs and H/F sides of this discussion in depth. It is really worth a read.
Getting to grips with ALAR

Regards.

Roland

P.S I understand that prevention is different ! But good SOPs should be universal.

[bsieker]

Originally Posted by Lemurian

There is, from the FDR a glaring takeover by the F/O.

Originally Posted by bsieker

Yes, but this is most likely not a causal factor in this accident, although very interesting to note in itself, and will be subject of investigation into training procedures, etc. at TAM.

Originally Posted by Lemurian

Can't it be also a factor in the delayed application of pedal brakes ? The time tags for stick inputs and braking seemed to indicate that possibility.

We have too few facts about the mode of this Takeover. In the CVR transcript there is no "I have control" or similar callout, which, particularly in a side-stick cockpit, must be called out in one form or another during a transfer of control.

So it is almost impossible to say what, if any, effect this may have had on delaying braking. So it is not included in the graph. But I think I'll give it some more thought. Thanks for pointing me to it again.

The only conclusion is that these instances indicate attempts -successful - at using differential braking for directional control, which seems to confirm the slipperiness of the runway (I still haven't given-up on the presence of aquaplaning ).

At 100+ knots the rudder would still have significant influence on directional control, I assume?

We still consider aquaplaning a possibility (so it is in the graph), but again, this has yet neither been confirmed nor denied. A comparison of wheel speed (if recorded), actual (A/S-limited) brake pressure and possibly other factors will tell.

I started as early as the 10th of august : See posts 1410, 1508, 1525.

Oh, yes, I remember, about the stick-control take-over. But, now as then, I cannot comment on that, other than that I find it interesting to see a complete takeover without callout.

Would be interesting to know if the priority-takeover pushbutton was pressed, and, if so, if the deactivated stick's inputs are still recorded, or suppressed even on the FDR?

Have to go now, but I submit this document to your perusal and study, as it covers most of the oPs and H/F sides of this discussion in depth. It is really worth a read.

Getting to grips with ALAR

Thanks a lot for this, it looks indeed very interesting.


Bernd

[Flight Safety]

What follows is a timeline analysis of the few seconds before and after touchdown, that might explain how a failure to retard ENG2 TL may have occurred, by failure to recognize thrust lever mode (or state) change from a switch function to a throttle function for ENG2 TL (left in the CLB detent), as I've discussed in previous posts. There have been several good theories discussed as to why ENG2 TL was left in the CLB detent, and I thought it prudent to attempt to "apply" the theory I've put forward to the actual CVR and FDR data. I also think theories that there was an electrical or sensor fault in detecting ENG2 TLA cannot be discounted at this point either. Hopefully we'll know the actual causes once the investigation is complete.

I assume from reading the CVR transcript that HOT-1 is PF and HOT-2 is PNF.

18:43:04 - HOT-1 (PF) remember, we have only one reverse.
18:43:06 - HOT-2 (PNF) yes...only the left.

Verbal reminder for both pilots that they only have one reverser discussed about 5 minutes 20 seconds before touchdown. Auto Thrust is activated and remains activated until after touchdown. Everything seems normal until close to touchdown, so I'm picking it up at the RA twenty callout.

18:48:21.0 - FWC twenty.
18:48:21.6 - FWC retard
18:48:22 - FDR - beginning of ENG1 TL movement to idle
18:48:23 – FDR – beginning of ENG2 increase in power
18:48:23.0 - FWC retard
18:48:23 - FDR - L-MLG WOW
18:48:24 - FDR - R-MLG WOW
18:48:24.5 - CAM [sound of thrust lever movement]
18:48:24.9 - CAM [sound of increasing engine noise]
18:48:25.5 - GPWS retard
18:48:26 - FDR - beginning of ENG1 TL movement to reverse
18:48:26.3 - CAM [sound similar to touchdown]
18:48:26 (between 26 and 27) - FDR - NG WOW
18:48:26.7 - HOT-2 (PNF) reverse number one only
18:48:27 - FDR - ENG1 TL in reverse

If I understand the A320 correctly, the retard callout should occur at RA twenty (it's RA thirty for the A340). According to the FDR data the movement of the ENG1 thrust lever begins about 1 second after the retard callout begins, around 18:48:22. Perhaps this movement didn't make a sound loud enough to be picked up by the CAM until 18:48:24. From the FDR data, this movement is the ENG1 TL being moved to idle, which is reached around 18:48:24.

It seems strange to me that the sound of increased engine noise at 18:48:24.9, which corresponded with a rise in engine power of ENG2 from the FDR, does not seem to get the attention of the pilots, as they make no comment about it, nor do they seem to take any action regarding it, because increasing engine power in the flare just prior to touchdown is pretty abnormal, unless your attempting a go-around from the flare. I think the pilots should have both heard and felt the increase in engine power.

The engine noise increase (as picked up by the CAM) occurred about the same time as the ENG1 TL reached the idle position. The FDR data shows the engine power started to increase about a second before the CAM picked it up, during the thrust lever movement to idle. The ENG2 power increase makes sense in light of the fact that the Auto Thrust System was still engaged at this point and a decrease in power on one engine would cause an increase in power of the other engine to maintain airspeed. Some have commented about the spike in power of ENG2 to EPR 1.24 or 1.25 at around 18:48:27 before settling to EPR 1.19 This looks like simple overshoot to me, common in many automatic systems.

Since according to the CVR and FDR, the pilots made no comment and took no action regarding the increasing engine power (which I think they would have heard and felt), I wonder if they were expecting it?

One possibility to explain why they might have been expecting it could be they got "creative" with the thrust levers (outside of Airbus procedures to retard both TLs) by trying to deploy ENG1 TR as soon as possible after touchdown. Both their actions taken and the comment made at 18:48:26.7, strongly suggest that getting ENG1 TR out as soon as possible was the goal of the PNF. Could he (PNF) have thought that the Auto Thrust System was still engaged when he started to move ENG1 TL back to idle (just above touchdown), thus leaving the ENG2 TL in the CLB detent on purpose so the ATS would continue to maintain airspeed (which the ATS did until ATS disconnect after touchdown)? Perhaps he didn't want to unsettle the flare just prior to touchdown, in order to get a good touchdown in the prevailing conditions, while still deploying the TR as soon as possible.

Another possibility is that the sound and vibrations of engine power increasing could have been associated with Reverse Thrust on ENG1 in the pilot's mind, as insidious as this scenario sounds.

18:48:29 (between 29 and 30) – FDR – Auto Thrust System disconnects
18:48:29.5 – HOT-2 (PNF) spoilers nothing
18:48:30.8 – HOT-1 (PF) aaiii [sigh]

The timeline at 18:48:29 and 18:48:30 re-enforces my belief that the pilots missed the state change from the thrust levers changing their mode (or state) from being selector switches to throttle levers. The state change happened at about the same time that the PNF called out “spoilers nothing”. This callout would have been shocking to the pilots, as both of these very experienced pilots would know in an instant what no ground spoilers meant in the prevailing conditions. The “sigh” from the PF suggests immediate recognition of those consequences.

This shocking and immediate turn of events could easily take the mind away from recognizing any state change in the working of the thrust levers, or recognition that the ATS has just disconnected and thus the ENG2 TL HAD to be pulled back to idle to activate the ground spoilers and auto brakes. If the increased engine power noise from ENG2 was associated with the TR from ENG1, how insidious this would have been, as it would sound and feel close to normal for thrust reverse.

I still argue that one habituated reason to leave an A320 thrust lever in the CLB detent is because it “lives” in that detent (as a selector switch) most of the time while an A320 is operating. It is also THE most common position to leave the thrust lever in when the Auto Thrust System is operating. On an all moving throttle lever system, the thrust levers don’t “live” in any particular position in the quadrant, and are thus habitually always thought of as throttles.

[Dani]

Very good theory.

I must add that pilots don't "feel" trust but rather hear noises and feel accelerations. So for me it's obvious that they heard the noise of spooling up and assumend that it was the reverser. What they felt was the missing deceleration. That's why they concentrated immediately to the available means of breaking, i.e. spoilers, reversers and breakes (auto and manual). In this order, since it is to be checked according SOP.

My theory goes this way: The captain had a plan in his head: I must go assymetric, 1 in revers, 2 in idle. He knew that there would be an assymetric power constellation on his pedestral. In time stress of the flare towards the short and slippery (?) runway he got it wrong: instead of 1 in revers 2 in idle, he did 1 in revers, 2 in clb. Which is just one little mistake for the hand, but one huge error that killed them.

I think in real life I would go both in reversers, although AI doesn't recommends it, but you avoid such assymetric manipulations. It's been proven by the junior captain one sector before. I do the same in OEI cases as soon as the failed engine is secured and stopped. AI is generally biased towards "double protection" (e.g. switching of a transponder on gnd altough it's connected to WOW, or putting out the nose light altough its off if gear is retracted, aso). This is also one of these cases. Makes technically sense. But is a possible cause for errors for some pilots not completly sure about SOPs.

Dani

[bsieker]

Originally Posted by Flight Safety

Could he (PNF) have thought that the Auto Thrust System was still engaged when he started to move ENG1 TL back to idle (just above touchdown), thus leaving the ENG2 TL in the CLB detent on purpose so the ATS would continue to maintain airspeed (which the ATS did until ATS disconnect after touchdown)? Perhaps he didn't want to unsettle the flare just prior to touchdown, in order to get a good touchdown in the prevailing conditions, while still deploying the TR as soon as possible.

The flare is supposed to be performed at idle thrust.

Reducing thrust doesn't "unsettle" the flare, it is an integral part of performing it.

Having higher positive thrust instead will cause the aircraft to float longer, and touch down later, faster and lighter. None of this could have been desirable here.


Bernd

[bomarc]

there is one small advantage to having had some thrust at flare...the engines will be slightly more quick to spool up once reverse thrust is selected.

[SIDSTAR]

Outstanding discussion, especially from ELAC, Bernd, ChristiaanJ, Flight Safety et al. I'm sure we have all learned a huge amount about both the accident itself and the workings of the A320 (auto) thrust system. The whole 100+ pages should be compulsory reading for all Airbus pilots. Danny, the whole reason for having Pprune in the first place is eloquently proved by the contributions of the above gentlemen - thank you all.
If one discounts the possibility of a fault in the thrust/thrust lever system (I'm not discounting the possibility but it is a long shot), then the investigation must centre on the "WHYs."
Why did the PF leave the lever in the climb detent?
Why was his mind set in that direction?
What was it about the system that had him thinking in that way?
Why did Airbus design it that way?
Having flown both Airbus and Boeing types in the past 5 years including the 320, I am convinced that the non-moving thrust levers are not a good idea. Someone asked a long way back why it is that Airbus designed the system this way. I seem to remember that one of their sales brochures mentioned that it was simpler (no back-drive mechanism to go wrong), thus lighter and of course cheaper but I cannot find the reference now.
Having also watched many pilots new to this system, operate the aircraft very poorly in both sim and aircraft, with little or no idea of what actual thrust the system was giving them, I am convinced that the design is inherently faulty. The essential cues of a moving lever are missing from the pilot's sensory system particularly in the most critical areas - approach and landing.
I've lost count of the number of times I've covered the EPR/N1 gauges and asked the other pilot what his power setting was, only to discover he had absolutely no idea. The system sucks you into believing that it will always look after you.
The tactile, aural and visual cues given by the thrust lever position cannot be over-emphasised, in my opinion. Having read the whole thread from day one, I find it very difficult to believe that this is not seriously implicated in whatever thinking led to the No 2 being most probably left in the CLB position. This is not anti-Airbus - one has to remember merely the ridiculous config/cabin altitude warning horn on the 737 to see that bad design affects both manufacturers - but it surely is an area that must be looked at in a critical manner after a number of such incidents/accidents. If not, I fear we will be discussing a similar accident in a few years time. The confusion that reigned on the TAM flight deck after touchdown should not be possible on any modern airliner. Unfortunately, such mode/situational confusion is common on many types. Professional pilots and the travelling public deserve better. Airbus and Boeing please do not forget the fallible humans at the front end and design man/machine interfaces that take full account of our human frailties. Your machines are technically excellent in most areas and rarely fail catastrophically. Can the same be said for the humans?
SID
ps It is also worth bearing in mind that Airbus and Boeing are not above using forums such as this for their own purposes, especially after an accident such as this. Major corporations don't have morals or scruples - only 'interests'.