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Old 3rd Oct 2007, 08:43
  #2645 (permalink)  
EMIT
 
Join Date: Aug 2007
Location: The Netherlands
Age: 63
Posts: 287
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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