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TAM A320 crash at Congonhas, Brazil

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TAM A320 crash at Congonhas, Brazil

Old 1st Aug 2007, 10:01
  #801 (permalink)  
 
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Before this accident happened, asking ten 320-drivers what would happen during landing with one TR inop, that TL in CLB notch and reverse activated on other engine.

I assume we would have get 10 different answers....
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Old 1st Aug 2007, 10:07
  #802 (permalink)  
 
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Spoilers didn't work
AutoBrakes didn't work
as is to be expected, giving the spoilers/autobrake diagram. One input FALSE, output FALSE (not in that it is the wrong output, but as in the logical value FALSE).

The FP tried to stop the plane with manual brakes...
strikes me as odd that I have not seen a "manual brakes applied" input in the abovementioned logic diagram.. have I overlooked it?

But an AB's computer system failure is not descarded by investigators, who said that it is possible that the system failed to identify the actual right engine TL position
now that's one thing that has bugged me for a few days now.
Can anyone shed some light on how the T/L readout is done actually? Are there redundant sensors? How many? Different physical principles?

pj
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Old 1st Aug 2007, 10:08
  #803 (permalink)  
 
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Originally Posted by hetfield
Before this accident happened, asking ten 320-drivers what would happen during landing with one TR inop, that TL in CLB notch and reverse activated on other engine.

I assume we would have get 10 different answers....
I assume you would get 10 pilots saying that they'd never do that...
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Old 1st Aug 2007, 10:11
  #804 (permalink)  
 
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I assume you would get 10 pilots saying that they'd never do that...
which is even more scary, and I actually thought we'd be beyond neglecting the fact that we all err at times.

pj
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Old 1st Aug 2007, 10:47
  #805 (permalink)  
A4

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Quote: My whole point is that the sequence following from this is made possible by the way the AB systems work, and maybe by the fact that pilots are trained to accept the counter-intuitive fact that under normal operating conditions, the T/L setting has no direct relationship with the actual engine thrust setting.
All you AB pilots out there, hasn't that been counter intuitive to you when you got your first AB rating? It would seem so for me.
After all, what we call intuitive is often just our past experience that has gone subconcious.


I think the only counter intuative thing that occurred here was (to be confirmed or not by FDR) that ONLY ONE THRUST LEVER WAS RETARDED!!!!. Now that has to be one of the most counter intuative things for any pilot to do. If this does prove to be the case, I fear we will never know why because the crew are not here to explain

For non pilots - if you approached a junction in your car and there was another vehicle in front would you apply the brakes? OF COURSE you would - it would be counter intuative not to would it not? If you didn't apply the brakes and then hit the other car ... would it be the cars fault?

I fear that the crew would have had all the cues that things were normal i.e increasing engine noise associated with selection of reverse - except that No2 was not providing reverse........ but the only cue would be lack of deceleration.

The AB THR LVRs are "unconventional" but simple in their operation. There have been many comments about design and logic but if you disconnect A/THR and move the lever to, say 30°, what would you expect to get? Right - commanded thrust by TLA (Thrust Lever Angle). That's why during conversion you are taught the correct way to disconnect A/THR - match the "donuts" THEN hit the disconnect button- otherwise you will get TLA thrust straight away.......... so on landing when BOTH levers are moved to idle, the autothrust disconnects (automatically) and your TLA (i.e. "Commanded thrust") is..... 0°, hence idle.

Awaiting the FDR data.

A4
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Old 1st Aug 2007, 11:05
  #806 (permalink)  
 
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Thanks, A4, for the car example.
They work exeptionally well in all forum discussions.

To be a little more fair to the situation:

If as a motorist and owner of a specific brand, you were taught never to touch the brakes or gas pedal other than upon leaving/entering the driveway and entering/exiting the motorway, would that make you more prone to forget something at some point?

I am not at all questioning the fact that leaving one T/L in a forward position is completely outlandish. But, unless there's evidence that it was a TLA sensor malfunction, it seems that it has happened.

And the point I am, once again, trying to make is: some of the design decisions in the AB system seem to have contributed to the fatal chain of events that has been started by this one mistake.

You point out the procedure to disconnect the A/T
-match the donut
-disconnect

If the T/L were moving, that procedure would not be required, the thrust commanded by the TLA would always match the thrust commanded by the A/T. No need for a procedure. (and btw, TLs moving back into idle as by A/T would also have avoided the spoiler/autobrake inhibition).

So to me, again, no professional pilot but very used to many kinds of complex software and computer systems, the AB system seems to be less than forgiving for this specific error.

pj
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Old 1st Aug 2007, 11:22
  #807 (permalink)  
 
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flyingnewbie10 and Dreamland are now entering into the realm of fantasy flight safety, where the ultimate solution is to ban flight altogether.

On a fully serviceable A320, if you leave one T/L in the CL detent and select reverse on the other on landing, you will get exactly the same result in terms of engine thrust behaviour and operation/non-operation of stopping devices. One thrust reverser inop makes no difference.

By denying the use of A/THR on approach and landing you take away a proven safety system for no reason, and increase the level of risk.
Airliners have been flying for years with various items of equipment inop, subject to MEL rules, and always at the Captain's discretion.
TP
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Old 1st Aug 2007, 11:29
  #808 (permalink)  
A4

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Quote: So to me, again, no professional pilot but very used to many kinds of complex software and computer systems, the AB system seems to be less than forgiving for this specific error.


Ok. But how far do you take it? This design is now almost 20 years old. It has been used millions of times without incident. There are now 4 instances of "mishandling" leading to accidents. Is it reasonable to now re-design what is actually a very safe system?

Your analogy to the car brand where you only touch gas/brake when leaving the driveway is not representative here. There is NO DIFFERENCE in the way you land a Boeing or an Airbus. Upon landing, at approx 20 feet, reduce thrust to idle. Period. No difference.

If you drive a manual car what happens when you put your foot on the clutch but leave it on the gas pedal - commanded "thrust". When you learn to drive what is one of the fundamental things you are taught........ clutch down - gas off..........

I have to go... will pick this up later.

A4
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Old 1st Aug 2007, 12:02
  #809 (permalink)  
 
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Ok. But how far do you take it? This design is now almost 20 years old. It has been used millions of times without incident. There are now 4 instances of "mishandling" leading to accidents. Is it reasonable to now re-design what is actually a very safe system?
if investigation did show that this specific design decision did not actually increase security but has contributed to catastrophic accidents like this one? Yes, absolutely.

I do, however, not know what the original decision was. Was it to spare the cost and weight of the TL actuators? Not very probable, but maybe. Was it in the hope to make the cockpit more ergonomical? Then it might have the be thought over.

Your analogy to the car brand where you only touch gas/brake when leaving the driveway is not representative here. There is NO DIFFERENCE in the way you land a Boeing or an Airbus. Upon landing, at approx 20 feet, reduce thrust to idle. Period. No difference.
yes, I know it was irrelevant. Any car analogy is irrelevant. Cars are by far less complex than any airplane.

If you drive a manual car what happens when you put your foot on the clutch but leave it on the gas pedal - commanded "thrust". When you learn to drive what is one of the fundamental things you are taught........ clutch down - gas off..........
And I'll be the first to say that I've already managed to kill off the engine by letting go the cluch with one foot on the brakes. I've scared everybody in the car by firmly stepping onto the clutch pedal, only that it was the brake pedal as I was driving an automatic car. It doesn't happen every day, but it has happened.

We all make mistakes and it should be the top design rules/goals of any complex system to #1 prevent error whereever possible, #2 tolerate single errors where #1 is impossible and #3 fail gracefully if #1 and #2 are impossible.

In this case, the design change could be that a "manual brakes applied" overrides the "one TLA >22.5°" ground spoilers/autobrakes inhibition and maybe at the same time idles the engine, while I'm not too sure about that.

pj
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Old 1st Aug 2007, 12:08
  #810 (permalink)  
 
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http://www1.folha.uol.com.br/fsp/cot...0108200701.htm
(It requires login/password, therefore I'll copy/translate here the most important things)

1 - FDR confirm one TL above idle (1st possible mistake)
2 - Only working T/R was activated. (2nd possible mistake)
3 - Pilot tried manual break

About the VDR (only press trancripts, so until I can hear the original audio we can't be sure of anything)

1 - At touchdown, one of the pilot says "Reverser one only".
2 - After that, they say "Spoilers?? nothing..."
3 - Them "Stop it !! Stop it !! I can't.. I can't... Turn... Turn..."
Last words were not released and surely won't help us...

The most important thing, but as I said before can't be take as guaranteed yet, is that someone said it's possible to hear in the VDR: "I can't move the TL, it's rolled."

If that's true it could mean they were aware of the TL in the wrong position but couldn't do anything about it...

Let's wait untill a full FDR/VDR is leaked so we can see/hear for ourselves...
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Old 1st Aug 2007, 12:13
  #811 (permalink)  
 
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What is a "rolled" thrust lever? Haven't seen those anywhere yet.
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Old 1st Aug 2007, 12:16
  #812 (permalink)  
 
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hmm.. duwde, what's the portuguese expressen for "it's rolled"?
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Old 1st Aug 2007, 12:18
  #813 (permalink)  
 
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Question

Just a thought.What was the crews duty times at the time of the accident.?
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Old 1st Aug 2007, 12:22
  #814 (permalink)  
 
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Pira - Thanks for the Gen.
The call "Reverser 1 only" if a command, is incorrect according to the latest MEL.
Both Reversers are now pulled. At least that is what has been posted here.
As regards the a/c 'Retard Retard' call out maybe AB can program the software to say 'Retard Number 2(1) Retard Number 2(1)". if that TL was still above idle.
Jim

Last edited by James7; 1st Aug 2007 at 13:18.
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Old 1st Aug 2007, 13:26
  #815 (permalink)  
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Let's wait untill a full FDR/VDR is leaked so we can see/hear for ourselves...
At the moment the FDR/CVR data has not been OFFICIALLY released, that question is being argued by the Parliamentary Inquiry right now, along with blaming each other for the leak. The data was "supposed" to be locked in the Committee safe until the Inquiry convened this morning at 0900 local.

So, while Folha is relatively trustworthy, we don't know who leaked the data, how much of it they leaked, and why they leaked it. There are a lot of vested interests at work here, so I would be very cautious about drawing any conclusions from this data, which may or may not be complete.

As duwde says, better to wait for the official release.

ab
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Old 1st Aug 2007, 13:49
  #816 (permalink)  
 
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-translated from duwde 's link


Black Box of the Airbus indicates pilot error

Computer registered imperfections in the operation of the thrust levers of the turbines; hypothesis of mechanical error is not discarded

Without control, the pilot tried to stop the airplane pressing the two pedals in its front, braking the tires of the landing gear


FERNANDO RODRIGUES OF THE BRANCH OF BRASILIA

The black box of the TAM Airbus-A320 that crashed in Săo Paulo on the 17th indicates that it had error from the pilot in the operation of the thrust levers, besides catching the desperation of the pilots in trying to brake the airplane on the ground. Although less probable, one pane in the computer of the airplane also cannot be discarded, separately or in set with the probable human error.
A Folha had access to the data, that had arrived yesterday at the Congress in a CD-ROM with about 60 archives of data and audio. The first failure, whose hypothesis had been anticipated by A Folha last week, occurred little before the landing, when the thrust lever of the right engine was kept in an acceleration position. It would have to be in idle, as the other lever.
When landing, the electronic systems had interpreted this procedure as a desire of the pilot to speed up. The two turbines had started to speed up automatically. The air brakes had not been set in motion. The automatic brakes from the landing gear also did not function.
A second mistake may have contributed for the abnormal acceleration: only the left turbine thrust lever was placed in the position of maximum reverse. This turbine had the reverser functioning, equipment that assists the braking when inverting the air flow in the turbine, - the other one not.
Even with the inoperative reverser in the right turbine, the correct procedure must have been to place both thrust levers in reverse. But the right remained speeding up, according to register. Airbus divulged a message last week alerting operators of its airplanes exactly on the necessity to fulfill these two operations, established already in preliminary data of the black box. It had other similar accidents with the A320 attributed the pilot error. The airplane of TAM had the right reverser deactivated for four days, because of a hydraulic problem.
Losing the control, the pilot then tried manual braking to stop the airplane. At the same time, with the hands, he held hard the internal mechanism could that controls the direction the front wheel. But the turbines had continued to speed up.
Last week, the responsible Brigadier General for the inquiry, Jorge Kersul, said that the hypothesis of failure in the computers is not excluded. “The data of the parameter can indicate that lever was in such position, but who can say that the problem was not electronic? Thrust lever can be in another position and the problem could be the electronic signal that the computer is emitting. People can hear something [in the voice recorder] that “thrust lever does not leave the place, its locked”, said to the CPI of the Aerial Apagăo. The audio archive that A Folha had access discloses that the pilot and the copilot emit laconic but important phrases. When touching the ground in the main runway of Congonhas, a voice in the cabin says: “Reverse one only”. That is, the pilot and the copilot knew that only a reverser was operative. After that, another phrase: “Spoiler nothing…”. That is, spoilers (air brakes in from above part of the wings), that they open automatically in the landing, had not functioned. The tone is dramatic: “slow down, slow down, slow down”. It increases the panic: “It does not, it does not, it does not”. Finally, the known phrase already: “turn, turn, turn”. Who heard the complete recordings and passed the content to A Folha did not want to disclose the final words caught at the flight deck, seconds before the airplane blowing up, killing 199 people.
The data will be analyzed today by the members of the house of representatives with aid of technician of the BAF. Beyond the human error and eventually of computers, a third hypothesis has derived from the previous ones. The pilot would have really pulled the two levers to the correct position at the time of the landing - the known position of “idle”, or “dead spot”, in Portuguese. For some defect, the right lever would not have been pulled back enough to emit the electronic signal for the computer. When an airplane as the Airbus-A320 approaches the runway to make a landing, the pilot and the copilot must introduce the data regarding to the landing. At this moment, levers can still be in the so called “climb” position, which means “to go up”. The computer knows that the flight is in the end and decelerates the turbines. However, when touching the ground, it’s important that the two levers are then in the “idle” position. The black box indicates that the right lever was still in the “climb” position, or “near idle” (almost decelerated) when the Airbus touched down. At this time, when the weight of the aircraft sets in motion the hydraulic systems of the landing gear, the computer is programmed to set in motion the air brakes (flaps and spoiler) and the wheel brakes. Nothing of this happened. As soon as the Airbus touched the ground, the two turbines spooled up. One of them had the reverser out (of the left side) and the air flow started to be inverted, helping the airplane to brake a little. On the right side, however, the turbine continued to increase the force, as if the airplane was making a new take-off.
For the attempt of the pilot in “holding” the airplane, it is possible that it has careened to the left at the start of the landing. Regarding Congonhas airport, black boxes have not yet ended up the controversy.
But the fact that the pilot managed to keep the airplane on the track indicates that the track couldn’t be that much below standard.
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Old 1st Aug 2007, 13:49
  #817 (permalink)  
 
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3 - Pilot tried manual break
IIRC, TAM has/had as a procedure to use manual braking, instead A/B whenever it is wet, mainly due actuation delay time. Well, at least that's what I heard through the grapevine.

Let's wait until a full FDR/VDR is leaked so we can see/hear for ourselves...
ditto!

BF
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Old 1st Aug 2007, 14:44
  #818 (permalink)  
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“thrust lever does not leave the place, its locked”,
- puzzled as I am by this 'quote', albeit from an incomplete release from an unofficial source, could an AB pilot tell me please:

What actions are required to move the AB 320 T/L from 'CLB' to 'IDLE'? Is there a latch that needs to be released or should it be a straight easy movement?

How is reverse actuated ie what is the actuating mechanism on the throttle quadrant?

How is reverse N1 adjusted?

Is there any mechanical 'drive' to the T/Ls in any mode?

When the CVR has been fully analysed, the timing of that 'quote' could be very significant.
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Old 1st Aug 2007, 15:00
  #819 (permalink)  
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is it possible for the thrust lever to be locked into the climb detent, perhaps as a function of landing with thrust lever in climb?
No
and again, will someone confirm that you cannot manually deploy spoilers in config-full?
Today 14:44
Yes you can, but the logic is you don't need to.
Yet again, we must acknowledge the fact that for whatever reason, they appeared to disregard the MEL operational procedures.
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Old 1st Aug 2007, 15:17
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Pira:
I have just finished seeing a CBT presentation on AB auto flight systems and it looks as the A/TH will do exactly what you suggested: if A/TH is disconnected with TL on CL detent, the engines will follow the TL position and accelerate. On approach, this kind of logic, may easily induce the crew to a feeling that the TL are at idle position (or almost there) as the engines will be running at lower power. The pilot had on is mind the RH REV problem and got himself ready to T/Rev the LH engine only (..." I have to remember that after touch down the RH engine should not be touched"). As there is no visual clue on TL quadrant what automation is doing at any time, I really feel that must be software changes to avoid that human factor and automation might be out of sync and cause this sort of tragedies.
In my opinion, AFT just landed, on ground, with a T/REV FULL DEPLOYED IN ONE ENGINE, IS COMMITED TO LAND. THE OPOSITE ENGINE SHOULD NEVER BE ALLOWED TO ACELERATE and BRAKING RESOURCES SHOULD BE FULL AVAILABLE TO PILOTS...in addition, the faulty REV on RH engine was known before the accident. Must be a way to tell the computer that a certain Engine Rev is INOP so that the automation follow a routine in such way that even if the pilot try to reverse a declared faulty engine it will never accept and braking capabilities are not limited....a lesson should be learned from previous tragedies, with very similar reasons.
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