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TAM A320 crash at Congonhas, Brazil

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TAM A320 crash at Congonhas, Brazil

Old 2nd Oct 2007, 15:15
  #2641 (permalink)  

Sun worshipper
 
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Mäx Reverse,
When the A320, it's ECAM/FWC and the basic ECAM-Handling were designed, a couple of warnings/procedures dind'nt yet exist, either because AI didn't know or admit they were necessary. These warnings/procedures found their way into the books 'the hard way'. Unfortunately some of them didnt't fit into the procedural model of the FCOM-preface. Of course they were introduced anyway.
Isn't that what product improvement is about ?
In my experience with the 'Bus, the *Loss of Braking* procedure is one of the only two design improvements that led to a procedure, the other one being the recommendation of config 3 for approach in gusty conditions on a 321. Both procedures are now fading away as the new constructions and new FMGC software have corrected the defect (318-type of steering / brake system and relaxation of the AoA trigger for rapid sidestick inputs, post the Bilbao incident).
As far as I know, even the event that has been a lasting impact in Germany has been corrected by a change in the air/ground logic, not by a new procedure.
But still, we are talking about emergency here : Memory items, of which the only phase 8, 9... item is the loss of braking. No alarm for it.
The rest of the memory procedures are :
  • Emergency Descent
  • Pull-up TOGA
  • Windshear TOGA
  • TCAS resolution
  • Aborted T/O
  • Unreliable IAS
  • Compressor stall
Of these, only Windshear TOGA and TCAS relate to a specific warning, out of the original design.

Last edited by Lemurian; 2nd Oct 2007 at 15:38.
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Old 2nd Oct 2007, 17:44
  #2642 (permalink)  
 
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Lemurian said:
Of these, only Windshear TOGA and TCAS relate to a specific warning, out of the original design.
And none of these (in the A310, and I believe in the A320 as well) are ECAM warnings. They are other type of warnings or noticeable events.

In the QRH we can find the note that regulates the Memory Items initiation:

Note: Memory Items may be carried out by either pilot, since response time may be important for success. However, initiation of Memory Items must be called out by the PF.

In practical terms, this works like this: Either the PF calls for the memory items, or he performs them himself (calling simultaneously to be correct), because there are cases like a EGPWS or TCAS warning that require PF immediate action. But these aren't ECAM warnings.

I think the *RETARD* autocallout is itself more than sufficient warning to retard the throttles. If someone wants to come up with a new warning, I suggest that if after a while, only one throttle has been retarded, a 2nd autocallout should sound, louder: *BOTH, YOU DUMB ASS!*

That should do it.

(I'm not insulting the TAM pilots, let that be clear)
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Old 3rd Oct 2007, 01:47
  #2643 (permalink)  
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Originally Posted by 3Ten
think the *RETARD* autocallout is itself more than sufficient warning to retard the throttles. If someone wants to come up with a new warning, I suggest that if after a while, only one throttle has been retarded, a 2nd autocallout should sound, louder: *BOTH, YOU DUMB ASS!*
That (minus the extra wording! ) was basically what the Taiwan investigators recommended, 3Ten; that the 'Retard' call should just continue until it was complied with.

Instead, no doubt for good reasons, Airbus designed (but did not at that time introduce) a separate warning including an ECAM notice, a chime, and the Master Warning Light:-

"Airbus has developed a specific warning when one throttle is set to reverse while the other is above idle. This warning generates an ECAM warning "ENG x THR LEVER ABV IDLE", a continuous repetitive chime (CRC), and lights the red master warning light."

Presumably that is the ($5,000 cost) warning system that Airbus are now offering, and that TAM (and no doubt other airlines) will be installing. Hopefully it will be standard on new construction as well.

Personally I can't see any good reason not to install it. It has no potential to confuse anyone since (like the 'undercarriage not down' alert) it will only sound if someone has made a really basic mistake. The vast majority of pilots will never see it operate, except perhaps in training.
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Old 3rd Oct 2007, 01:54
  #2644 (permalink)  
 
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there are ECAM warnings, but what is more important, if we are talking about this accident, in case of a thrust lever angle sensor problem, the FADEC commands idle power for the affected engine, if the aircraft is on the ground and not in a take-off run (i. e. thrust before failure was above CLIMB).

The Thrust lever fault warning is not inhibited during landing. I don't know if the thrust lever disagree (if any or not equal to the thr lever fault warning) is not inhibited after touchdown, though.

Regarding the FADEC putting the engine in idle could one state whether or not this would happen even with a faulty desengagement and disconnection of the A/THR ?
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Old 3rd Oct 2007, 09:43
  #2645 (permalink)  
 
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A lot of points

On warnings.

For the people who consider new or revised warnings to be the solution -

What would you consider the highest priority warning that can occur in an aircraft?
I would say “WHOOP WHOOP – PULL UP!”
Boeing and Airbus agree with me, because that warning indeed has the highest priority in their warning schemes.

Read from an actual occurrence in a B-767:

Less than 2 minutes into the flight, GPWS warnings begin: “TERRAIN TERRAIN – PULL UP PULL UP – TERRAIN TERRAIN!”

The First Officer reacts with a gentle pull up from 9.3 to 12.5 degrees. After gaining 200 feet, he lowers the nose to 11.2 degrees, just before the airplane’s left wing clips the last 20 feet off a 300 foot antenna tower on top of a 3,000 foot mountain! After the impact, the crew raises the nose to 16.9 degrees and applies full thrust. (Luckily the airplane could be landed at the airport of departure).

OK, so you are convinced that a warning during a high workload phase such as touchdown and landing roll will solve the problem?

Additional concerns would be: an ECAM caution is inhibited at that stage, a warning not inhibited, but action is delayed until landing is complete, so you would have to seek it in a modification of the RETARD callout.
But if you make the mistake in the first place, the little green man uttering that call may well be correct in his estimation of your mental capacities and there is a good chance that his adapted message will not hit home.


On the subject of “gates” –


Yes, that is a good description of what goes on and it also will illustrate that a go-around from the given situation is not so likely as some people consider it to be.

As a pilot, you constantly evaluate what is happening.
Of course, you have evaluated the airport and weather situation and you have deemed the situation suitable for approach and landing. Gate satisfied, passed.
During the approach you evaluate whether you are within the normal bracket to continue the approach (speed, altitude versus distance, configuration, LOC and G/S deviation margins, etcetera). At the gate, approach must be stabilized (e.g. at 1.000 ft in IMC, at 500 ft in VMC). Gate satisfied, passed.
At approach minimum, visual requirements must be satisfied (e.g. runway sighted). Gate satisfied, passed.
Landing clearance must have been received. Gate satisfied, passed.
Landing must be in touchdown zone. Gate satisfied, passed.

All the above gates, if not satisfied, will lead to a decision to NOT LAND, but Go Around.

Instances where errors are made are often:
- The violation of the stable approach window if the unstable condition is due to crew error. If the error is due to external conditions, pilots seem to be easier inclined to go around. If they caused the problem themselves, they are usually very busy trying to correct their own error and the high workload deteriorates their estimate of the situation. Also, there may be a subconscious unwillingness to admit defeat.

- Not recognizing that the approach becomes unstable after passing the window (example: the Air France 747 at Tahiti).

- Not aborting the landing, if touchdown is going to be (way) passed the touchdown zone (example: Lufthansa A-320 in Warsaw).

Now, if the perfectly good airplane has been nicely landed right at the desired touchdown point, what else is there but to bring the aircraft to a full stop?
Landing gate satisfied, passed.

Of course, stopping attributes are checked for proper operation, but why should they fail, if the aircraft was in perfect order just a few seconds ago?
Spoiler deployment? Yes, the spoilers may hesitate if the touchdown is extremely smooth. Solution in Boeing, pull back speedbrake handle manually. Solution in Airbus, deploy reversers and Ground Spoilers will deploy.
Reverser deployment? Of course, one might fail, but both simultaneously, that falls into the 10 to the –9 times regime. Moreover, it would only be a slight nuisance, requiring perhaps a little directional correction.
Autobrakes (if selected) not functioning? Solution, manual braking.
Failure of all stopping attributes at the same time – that is gonna catch you by surprise!
Is every pilot ready for that event, making a touch and go out of a perfect landing with a perfect aircraft that all of a sudden seems to be completely broke? I am afraid not.

The Australian A-330 crew (details can be found on PBL’s website), they made an excellent decision to break off the landing attempt when their aircraft was suffering from the effect of water ingestion into the radio altimeter antennae. But please take into account that due to multiple bouncing touchdowns they fell into the situation that touchdown no longer was going to be properly in the touchdown zone!

In other words, once the good landing gate has been satisfied, passed, it is very hard to turn a crew’s intention 180 degrees around into a go around again.

Making such a decision is about the same as expecting a pilot to break off his take-off after passing VeeOne. That too is not impossible, imagine a very light aircraft on a 4.000 meters runway, but it is beyond the scope of normal line operations.



Now, something on books and procedures.

Many remarks have been made on why the pilots did not just follow SOP’s?

SOP means Standard Operating Procedure.

Flying with one Thrust Reverser de-activated is NOT SOP. It happens, not very often and it is no big deal, but it is not SOP.
What is SOP, is the procedure that you consult the MEL (Minimum Equipment List) to check whether you are allowed to operate with the deficiency and under what conditions. The MEL is a book that is not ready knowledge, it is a book that is consulted! (SOP’s are ready knowledge).
The MEL is a book that is not studied by pilots, so you will not know whether a certain procedure has recently been changed, what has been changed or why it may have been changed – you just follow the procedure as presently written down.

At this moment, …., well we have read it often enough by now, how to handle the thrust levers if a T/R is de-activated.

How do you use the MEL physically? In some companies it will be a thick book, in some it is accessed via the LPC laptop. Do you keep one or the other on your lap during approach and landing for consultation? Don’t think so. Either you jot down the important items on a piece of paper, or you commit them to memory.

In memory, more pieces of information are stored, perhaps the FCOM remarks about the (slight) increase in forward thrust when the T/L of a de-activated T/R is pulled into reverse range; perhaps a recollection of a simulator session in which both T/R’s were unavailable due to an hydraulic Green and Yellow failure and landing had to be made on the only available runway that happened to have reduced braking action as well and where stopping just prior to or just over the end of runway was determined by having yes or no pulled the T/L’s into reverse range or not.

Forget about MEL now and just look at a failure that occurs during flight: an hydraulic system Yellow failure. One of the consequences will be stated on the STATUS page: INOP SYSTEMS – REV 2.
Guess what kind of guidance you get on thrust lever handling? NADA.
Neither ECAM nor QRH nor FCOM 2 will give you any special procedures as to T/L handling. Do you consult MEL? No, you are not required, because MEL is a document to determine whether you can be dispatched with an un-rectified failure. MEL by definition is not for use once a flight has commenced.
So, thrust lever handling can then be determined by pilot knowledge – just do like always, both T/L’s into reverse, or, use your knowledge about thrust increase and do not pull the “faulty T/L” into reverse (remember when pulling faulty T/L’s into reverse was a bad thing during that SIM session).

So, IF pilots did decide to not pull T/L 2 into reverse range on a short and wet runway, would that decision have been “non SOP” or “a wise decision based on excellent system knowledge”?

Of course, if they had made a decision to not pull T/L 2 back from CLB detent, that would have been an appalling lack of system knowledge. We cannot ask the TAM guys anymore, but I have missed the answer to this question in the Bacolod and Tai Peh accident reports. Did the pilots consciously or accidentally leave the T/L in CLB detent. Was their intention to leave the T/L behind in the CLB detent, or at the idle stop?

To quantify the increased idle (approximate values):

Normal idle: N 1 - 22 % N - 2 57 %

Reverse idle: N 1 - 27 % N - 2 66 %

Note: values with a reverser deployed. Can not state with absolute certainty that values will be exactly the same if reverser was de-activated.


Now on FAA SAFO and JAA OD.

A couple of pages ago, someone has posted a copy of an FAA Safety Alert For Operators (SAFO). I have read no comments on this.

Perhaps everybody thought, yeah, we have seen that before, it is just copy number umpteen of that Airbus Accident Information Telex that 4 HolerPoler posted a month and a half ago.
Not so! (I’ll explain in a minute).

Just prior to the FAA SAFO, the Chief Executive of the Joint Aviation Authorities issued to all National Aviation Authorities a recommendation to issue an Operational Directive concerning the handling of thrust levers on the A-320 family in case of de-activated thrust reversers. The SAFO is the FAA response to that recommendation. Pilots in European countries may by now have been issued an OD by their national authorities – that depends on how quickly the paper mills churn.

What is the significance of this OD / SAFO?
Well, although the final report of Congonhas is not yet out, the Chief EXEC of the JAA clearly links CGH to “the other accidents” (no need in this forum to explain which ones) and states unequivocally that T/L’s were inappropriately left in the CLB detent.
So it must be pretty certain that all the mysterious failure scenarios can be shelved by now. Please acknowledge that the JAA is not a part of Airbus Industries.
Furthermore, the OD gives the long sought after answer to the question why the MEL procedure for de-activated reverser was changed and it explains painfully accurate the philosophy behind the increase by 55 metres of the required landing distance for contaminated runways.
****************************************
A copy of the JAA OD.

RECOMMENDATION BY THE CHIEF EXECUTIVE OF THE JOINT AVIATION AUTHORITIES TO NATIONAL AVIATION AUTHORITIES TO CONSIDER THE ISSUE OF AN OPERATIONAL DIRECTIVE CONCERNING THE HANDLING OF THRUST LEVERS DURING LANDING WITH A DEACTIVATED THRUST REVERSER FOR AIRBUS A318/319/320/321 AEROPLANES
The issuance of an Operations Directive (OD) is described within the JAA Administrative & Guidance Material under Section Four: Operations, Part Two, Procedures (JAR-OPS), Point 9.3.
EU Member States’ attention is drawn to Regulation (EC) No. 1899/2006 and 1890/2006, which amend 3922/91 Article 8. These measures affect ODs issued by NAAs.
Point 9.3.2 repeats the essence of JAR-OPS 1.015, namely, that OD's only may be issued by an (National Aviation) Authority.
Point 9.3.3 refers to information available to JAA on operational procedures or a type of operation which is thought to incur an unacceptable risk and how to deal with such information. In such cases, advice will be given to all Authorities that an OD should be issued with the aim of forestalling a suddenly perceived risk or danger. Details about origin and quality of information provided to JAA LO will be made generally available.
1. General
Based on the information provided to JAA LO Operations that is summarised below, JAA National Authorities are recommended to issue an Operations Directive (OD) for their respective operators.
2.
Reason for issue

The purpose of this OD is to emphasise the manufacturer’s recommended operational procedure to select idle thrust on both engines during a landing conducted with one deactivated thrust reverser.
Background:
There have been at least three similar accidents/incidents that have occurred because the flight crew failed to retard both thrust levers to the IDLE detent for the flare and landing when the A320 aircraft were dispatched with one thrust reverser deactivated as allowed by the MEL. The thrust lever corresponding to the engine with the deactivated thrust reverser was left in the CLIMB detent during the flare and touchdown. MAX REVERSE thrust lever position was selected on the engine with the operative thrust reverser. In each instance, the auto thrust system remained engaged in the speed mode until selection of reverse on one engine disconnected the autothrust system, and the thrust system reverted to the manual mode. This resulted in the thrust increasing within the range of the CLIMB limit thrust setting in order to maintain the selected speed. When the auto thrust disconnected, the thrust remained at the last commanded thrust level per the lockout feature. Ground spoilers did not deploy and autobrakes, if selected, did not activate. The most recent accident resulted in 199 fatalities.
The A320 autothrust system utilizes six detents: TOGA, FLEX/MCT, CLIMB, IDLE, REV IDLE, and MAX REVERSE to establish the maximum full authority digital engine control (FADEC) computed thrust for the ambient conditions. The thrust levers do not move automatically but are manually placed in one of the detents by the pilot. The A320 design requires that both thrust


JAA LO Page 1 of 2 13 September 2007 JAA LO Page 2 of 2 13 September 2007
levers be retarded to the IDLE detent by the pilot on landing to disconnect the auto thrust system, to initiate the system logic for the deployment of ground spoilers and the activation of autobrakes, and to avoid an undesired increase in thrust during the landing roll. In the case of dispatch with one thrust reverser deactivated, the MMEL and the recent Airbus Accident Information Telex (TAM JJ3054 AIT 4, August 2, 2007) each call for the pilot to set both thrust levers to idle for the flare and to set both thrust levers to maximum reverse at touchdown. In all cases, the system designed logic requires that both thrust levers be retarded to the IDLE detent for flare and landing. Pilots should follow operator specific procedures for the selection of reverse thrust.
It should be noted that the MMEL ops procedure was amended in 2006 to require both levers to be set to maximum reverse at touchdown when operating with one thrust reverser deactivated. This revised procedure was introduced to standardise and harmonise with the normal operating techniques when both reversers are serviceable, thereby minimising normal and MMEL dispatch procedural differences.
As can be seen from the MMEL procedure, this standardised procedure incurs an additional 55m to be added to the scheduled landing distance required, which is caused by the slightly increased N1 of the engine with deactivated thrust reverse. In practice, this increase in landing distance will not be observed since it will be more than cancelled out by the maximum reverse thrust selected on the engine with the serviceable reverser, but this effect cannot be acknowledged in the calculation of landing distance required as credit for the use of reverse thrust during landing is not permitted.
The MMEL Operational Procedures also contain the instruction that reverse thrust must not be selected when both thrust reversers are inoperative.
3. Applicability and duration
This OD is applicable to those aircraft dispatched in accordance with the MMEL for Airbus A318/319/320/321 item 78-30
This OD will be applicable until further notice.
4. Recommended actions in regard to Operations Manuals
Operators should take note of and ensure that all affected personnel are familiar with the content of this OD and of the relevant section of the MMEL.
Operations manuals should be amended to reflect current Airbus procedures in this respect.
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Old 3rd Oct 2007, 10:02
  #2646 (permalink)  
 
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Originally Posted by xulabias_bent
The Thrust lever fault warning is not inhibited during landing. I don't know if the thrust lever disagree (if any or not equal to the thr lever fault warning) is not inhibited after touchdown, though.
TLA fault is inhibited only between lift-off and thrust reduction altitude, TLA disagree is inhibited between 80kts and thrust reduction during take-off, and between touchdown and 80kts during landing.

Regarding the FADEC putting the engine in idle could one state whether or not this would happen even with a faulty desengagement and disconnection of the A/THR ?
The A/THR involuntary disconnection in this case was not "faulty". It was due to a failure condition, but one that is handled in the software. After that, A/THR is simply disengaged and disarmed, with a thrust lock situation, as if it had been disconnected with the FCU pushbutton.

I haved described the complete behaviour in case of the thrust lever angle sensor problems in an earlier post, but here are the relevant bits:

- With TLA (at time of failure) below FLEX/MCT, on the ground or in flight with slats extended, FADEC commands idle power, regardless of autothrust engagement status.


Bernd
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Old 3rd Oct 2007, 14:05
  #2647 (permalink)  
 
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Great post EMIT, 99.9% agree with you.

Now, if the perfectly good airplane has been nicely landed right at the desired touchdown point, what else is there but to bring the aircraft to a full stop?
Landing gate satisfied, passed.


This is it, and from that moment on, after reverse thrust deployement, the aircraft is in a very low energy condition to decide to fly again, so there's an almost irreversible commitement to a full stop. If the runway was big enough to accelerate again, it would be big enough to stop as well, to put this in simple words.

Please, pay attention to posts like this, because this is the real description how flight progresses and how pilots work, this is not "in office" ellaboration.

Cheers
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Old 3rd Oct 2007, 15:13
  #2648 (permalink)  
 
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EMIT made a lot of points...
Thanks for posting the JAA OD.

For the people who consider new or revised warnings to be the solution -
Do you have a better solution?

OK, so you are convinced that a warning during a high workload phase such as touchdown and landing roll will solve the problem?
No, because the warning itself will not prevent mishandling - that requires ability and training. In your B767 GPWS example the warning was perfectly valid but the crew actions were not correct. Are you suggesting that lack of correct response to a warning means that the warning is not required?

Additional concerns would be: an ECAM caution is inhibited at that stage, a warning not inhibited, but action is delayed until landing is complete,
Here I really disagree with you and some other posters. Any warning requires immediate action. That action may be:
Do nothing except monitor the flight path, or
Take action to maintain or restore a safe flight path.
Remember Fly - Navigate - Communicate...?

so you would have to seek it in a modification of the RETARD callout.
I disagree. We often hear the RETARD reminder (some pilots use it, incorrectly, as the cue to retard the thrust levers) - a different, stronger warning is required.
A Level 3 warning means that "The configuration, or failure requires immediate action:" due to
"Aircraft in dangerous configuration, or limit flight conditions (eg: stall, o/speed)" or
"System failure altering flight safety (eg: Engine fire.. excess cabin alt)"

Whether a red warning is displayed on the PFD or ECAM is irrelevant - it is a warning requiring immediate action.
Note: I do not imply that you have to carry out ECAM actions immediately. But a red warning requires immediate action.
Get used to it, and brief for it if you are operating with one T/R INOP !!

Cheers
Tyro
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Old 3rd Oct 2007, 16:06
  #2649 (permalink)  
RWA
 
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Originally Posted by EMIT
OK, so you are convinced that a warning during a high workload phase such as touchdown and landing roll will solve the problem?
In this and other specific cases of one TL not being retarded, given that there is clear evidence that the pilots were confused and unable to identify what had gone wrong, yes, I'm convinced, EMIT. Otherwise the likelihood is that yet more people will be killed or injured when the same thing happens again.

Originally Posted by EMIT0
Additional concerns would be: an ECAM caution is inhibited at that stage, a warning not inhibited, but action is delayed until landing is complete, so you would have to seek it in a modification of the RETARD callout.
Now there I agree with you - and with Captain Chen, who was the lead investigator at Taipei. The simplest way would surely be to modify the existing 'Retard' callout so that it continues until BOTH levers have been retarded, instead of just one?

In that connection, thanks to PBL's excellent site, I just unearthed the report on the 'carbon-copy' Philippine Airlines Bacolod accident back in 1998. It's nowhere near as comprehensive as accident reports in other countries, but the relevant part of it reads:-

"ln the context of the accident approach in manual mode and A/THR engaged and at least one thrust lever is above idle detent, the 'retard' call out is emitted at 20 feet R.A. and continuously below this height until the aircraft speed reaches below 80 kts on ground.

- 2 thrust levers in idle detent, or

- at least one thrust lever is in the reverse range detent (this was the condition that stopped the 'retard' callout on the accident aircraft) (Annex B)."

http://www.rvs.uni-bielefeld.de/publ...olodReport.pdf

As I read that, had the Congonhas pilots landed and:-

1. Failed to retard one of the levers, but ALSO

2. Not decided or needed to deploy reverse thrust -

The 'Retard' call would have continued until the speed was below 80 knots.

But BECAUSE they deployed reverse thrust, albeit only on one engine, the 'Retard' call cut out.

Someone tell me the logic of setting things up that way - a continuous warning if you don't retard either lever, UNLESS you select reverse on even one engine.

The logic certainly escapes me. IMO, since it has been clear since Bacolod that lives can depend on it, the 'Retard' call should continue until BOTH levers are at 'idle.'
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Old 3rd Oct 2007, 16:20
  #2650 (permalink)  
 
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The logic certainly escapes me. IMO, since it has been clear since Bacolod that lives can depend on it, the 'Retard' call should continue until BOTH levers are at 'idle.'
I agree with you, I think that logic is nothing but a flaw in the system's architecture. I also think that simply repeating the callout may be inefective, as sometimes these cues become ignored by the pilots in stress conditions. So if that was the choice, disregard my previous wording , but introduce a louder and stronger autocallout.

But if we are in an a/c that has active protections and uses fadec, then why not make it so that once 1 thrust rev is deployed, the other engine is commanded to idle. I cannot think of a situation in the ground when this action would not be desireable.
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Old 3rd Oct 2007, 17:46
  #2651 (permalink)  
 
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Thats why I had proposed way back when that the RETARD call should not only continue (per the Taipei accident report ) but that if one of the levers is not in idle that that lever should be identified and the call would then be RETARD TWO, RETARD TWO, RETARD TWO (or RETARD ONE as the case may be) until it is idled.

this is probably the one thing that Lemurian has agreed with me on.
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Old 3rd Oct 2007, 19:37
  #2652 (permalink)  
 
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PAL A320 accident

Apologies if this incident has been raised before, but I came across a precis of it on Aviation Safety Network and it seemed relevant to this discussion.

Circumstances not dissimilar to TAM accident; acft overran, with fatal consequences (although in this case, 3 fatalities, all on the ground).

http://aviation-safety.net/database/...?id=19980322-0
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Old 3rd Oct 2007, 21:22
  #2653 (permalink)  
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Originally Posted by akerosid
Apologies if this incident has been raised before
Indeed it has. Most recently, in a post three and a half hours before yours.

PBL
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Old 3rd Oct 2007, 21:36
  #2654 (permalink)  
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Some people on this thread have expressed the opinion that the only significant causal factor was the failure of the crew to reduce thrust on landing.

To show how limited such a view is, I quote from the recently-issued U.S. NTSB Summary of their report on the December 2005 overrun at Chicago Midway:

Originally Posted by NTSB
Also, contributing to the severity of the accident was the absence of an engineering materials arresting system (EMAS), which was needed because of the limited runway safety area beyond the departure end of runway 31C.
The same obviously holds true of 35L at CGH.

PBL
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Old 3rd Oct 2007, 21:56
  #2655 (permalink)  
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Not 'limited', PBL - the NTSB said, as you know
The National Transportation Safety Board determined that the probable cause of this accident was.......
The lack of EMAS 'contributed' to the severity of the accident, not the accident. Even with EMAS there would have been an accident. Aircraft landed 'safely' there without the EMAS. They did not land 'safely' there when reverse was not used correctly.
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Old 3rd Oct 2007, 22:09
  #2656 (permalink)  
 
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TLs x Retard

I learned here that there are two conditons when "Retard" warning will cease:

1. Both TLs at idle

2. At least one TL at reverse.

If this is correct, why "Retard" warning ceases before condition 2 is met?
(per CVR @ 18:48:25.5)
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Old 4th Oct 2007, 00:11
  #2657 (permalink)  
 
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The SWA pilots were found at fault for delaying reverse at MDW causing the overrun. If they had deployed TR on touchdown they would have stopped with no problem. The computer wouldn't allow ground spoilers or auto brakes and questionable thrust control on this landing and it is also pilot error?
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Old 4th Oct 2007, 03:33
  #2658 (permalink)  
 
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Basic INSTINCTIVE airmanship in ALL airplanes. . .

. . .from day 1 of your flight training, single or multiengine, . . .in order to stop on the runway is to close/retard the throttle(s). It's an instinctive, elementary action that requires no thought processes and no bells and whistles as a reminder.

The two TAM captains were suffering from temporary insanity; there's no warning bells for that.

The debate as to why neither pilot closed both throttles can drag on infinitum, but it's stupefying.
GlueBall is offline  
Old 4th Oct 2007, 05:33
  #2659 (permalink)  
 
Join Date: Oct 1999
Location: Hong Kong
Posts: 67
Devil

Glueball
I agree with your post and for those that still want to go on and on about extra warnings, watch the animation of the SWA 737 on the NTSC website.http://www.ntsb.gov/events/Boardmeeting.htm
Another miscomprehension that some people seem to have is that autobrakes will stop you on the runway available no matter what. WRONG you are selecting a DECELERATION rate. On landing you will then normally use idle reverse / full reverse with ground spoilers (normally set to operate automatically to assist the pilot and save time) then take over braking manually depending upon runway conditions, length etc. The autobrakes are there to get the deceleration started earlier than perhaps a non "test pilot" could. Plus if you are using full reverse then depending upon the deceleration rate selected, the brakes may not be applying very much force as the "rate" selected is being achieved by other means i.e. reverse / spoilers / brakes.
electricjetjock is offline  
Old 4th Oct 2007, 06:06
  #2660 (permalink)  
PBL
 
Join Date: Sep 2000
Location: Bielefeld, Germany
Posts: 955
Originally Posted by BOAC
Not 'limited', PBL
Since you like to contradict me, allow me to contradict you.
Yes, limited.

There is apparently a lot you don't know about accidents and how they are conceived. Let me refer you to, for example, Nancy Leveson's book Safeware, Chapter 9, for a set of concepts, including that of accident, which are pervasive in the safety field. These are derived from a coherent reconstruction of standards in the U.S. Let me also efer you to my book, Causal System Analysis, a draft of which is on-line, Chapter 5, for a discussion of these concepts.

Originally Posted by BOAC
The lack of EMAS 'contributed' to the severity of the accident, not the accident.
This is a contradiction in terms. The definition of an accident includes severity. See Leveson op. cit., or even the U.S. criteria for mandatory reporting of a civil aviation mishap.

If you have Southwest landing in the absolutely identical circumstances and behavior on, say, a 5000 m runway, you don't have anything you could call an accident. You just have a lengthy landing. But to make sense of your statement above, since everything about the event would have been identical except the length of the runway and the severity of the event, you would still have to be calling it an accident. Doesn't make sense, does it?

You are also aware that the NTSB's prioritisation of one cause as "probable" and others as "contributing factors" does not fit the thinking about causality of accidents in its own land, let alone that of other investigating agencies or accident specialists in general. We have been through this before.

PBL
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