TAM A320 crash at Congonhas, Brazil

[bsieker]

Originally Posted by studi

It is entirely possible to have reverse on one engine (= not flyable) and climb power on the other (= not landable, no spoilers), which is definitively a state which is never ever desirable.

Not sure how Boeing is doing it, but it's really obvious that you should always have at least one of the two options, braking or going around.

Please read about the accident described only two posts before yours. In a B747 three engines were in full reverse, one at Go-Around thrust. This is a general problem, not specific to Airbus.


Bernd

[GMDS]

Lemurian, ANY airliner that I know add trust before they stall. Fokker 100 come to my mind, MD-11... I'm surprised that Boeing still doesn't do it. Maybe in the 787 finally... I'm so glad I'm not flying these oldtimers

Dani

Just for your info: B777 FCOM 9.20.11:
The autothrottle can support stall protection if armed and not activated. If speed decreases to near stick shaker activation, the autothrottle automatically activates in the appropriate mode (SPD or THR REF) and advances thrust to maintain minimum maneuvering speed

This means, on or off (not disarmed though), the AT of this "oldtimer" will add thrust when approaching stall and stick shaker.
It's tricky pretending things about birds you haven't flown yourself.........

[bsieker]

Originally Posted by EMIT

This accident at a rate of 1 per 17 million landings - no, the rate should be calculated versus the number of landings with one thrust reverser deactivated and the pilots using autothrust for the approach.
Rate would be closer to 1 per 17.000 landings then.

Perhaps.

But when we're looking at the thrust lever design, we cannot separate TR-inop landings from those with all systems functional. One cannot have a different set of thrust levers installed, or a different way of operations when one (non-critical) system is unserviceable.

So the statement stands that the thrust control system (hardware, software and wetware) has worked as per design in 55 million landings, and failed in this particular way in 3 landings. Mandating a change to the system cannot only take special situations into account.

So the relatively high failure rate at handling the thrust levers with one reverser inop has to be addressed, but not by changing the thrust lever system. More consistent procedures, and better training will perhaps be more effective. (More about procedures and reversers inop shortly ...)


Bernd

[Dani]

GMDS, I find it amusing the least that you blame me to saying something wrong about Boeing, since I stated before that ANY aircraft with Autothrottle has some sort of alpha floor protection, then some very smart guys (forgive me that I believed them) told me that it's not so, then I give in because I don't really know every aircraft and accept their information. Now you blame me for repeating their opinion? I was defending your system, do you remember????

Dani

[PBL]

Originally Posted by Dani

....... you blame me to saying something wrong about Boeing ....... then some very smart guys ...... told me that it's not so, then I give in because I don't really know every aircraft and accept their information. Now you blame me for repeating their opinion?

Yes, it does show the value of making sure one's information is correct *before* one posts it.

PBL

[Lemurian]

Of Alpha floor

Wait a minute !
There is a bit more than a misunderstanding here. The discussion started when Dani wrote :

Alpha Floor protection is nothing Airbus has alone. Most airliners with autothrottle have it, too. It is also no argument for a non moving trust lever.

.
*Alpha floor* refers to a mode that's quite specific, involving not only a go-around thrust application but also the triggering of a pitch submode that will keep the AoA below the onset of stall.
I still stand by my previous statement :

I do not know of any example outside the AI range of FBW planes and the Falcon 7X.

That some airplanes - and I'll confess that there were more than I expected - have some sort of *thrust application * (how much / when /which mode ?) it doesn't give them the Alpha floor protection as we understand it in AI products.

[GMDS]

Now you blame me for repeating their opinion? I was defending your system, do you remember????

Dani

I didn't blame you, mate. I said "it's tricky".

GMDS

[marciovp]

In the news today

The previous transcript of the voice recorder missed some time, perhaps the most dramatic one. The House of Representative Committee (CPI) heard the full tape recently, and after that they came to the conclusion that there was no HR in the disaster. They also learned that in the simulator the "retard" sign goes on until the TLs are in the right position while that in the TAM plane it stopped after repeating twice. From what they heard in the tape, there were dramatic moments with much despair and the pilots were very attentive to what they were doing. Finally they said that there was the noise of the TLs being placed on Idle. Here, in
portuguese-braziliam, the news:

http://si.knowtec.com/scripts-si/Mos...ata=2007-09-05

[Ben_S]

Not a pilot but the retard call not continuing has been discussed many times & is due to TAM not having the latest "software" on their planes.

[DozyWannabe]

Well that's settled, guess we can all go home now...

[Rananim]

As I said before,the denial from the Airbus camp has always been entertaining..One of them even accused me of putting before the cart before the horse.How ironic then that this aircraft gives you TR before TL's are at idle.If ever there was case of putting the cart before the horse,this would be it.But with 200 people dead and 3 precursory incidents/accidents the time for facing the truth will come soon.

An interlock mechanism in the thrust lever assembly mechanically prevents simultaneous movement of the forward and reverse thrust levers.The reverse thrust levers can be raised only when the forward thrust levers are in the closed positionRaising the reverse thrust levers to the reverse idle detent locks the forward thrust levers in position.

B747-400 OPS MAN vol 1 72.10.18
Applies to all Boeing aircraft.I already quoted 777 FCOM and I dont need to quote 737 as I know the machine like the back of my hand.

Studi,
You have my respect for choosing reason over bias.Loyalty to the type you fly should never interfere with honest appraisal.I stand by that and know that no manufacturer is perfect.
Boeing too has faults.Of course it does.The 737 single rudder PCU broke the redundancy rules.The non-automatic retraction of speedbrakes with TOGA thrust remains controversial(they retract automatically on the rwy GA scenario but not in the EGPWS escape maneuver-to cover themselves,they proscribe specific pilot actions when carrying out such a manuever).The failure to truly update the 737 and replace master caution with EICAS was lazy and penny-pinching but they have experts who consider all the angles.

That's exactly what the system did! One TL was not in idle. Hence no braking. As long as a pilot wishes to have more than idle, the aircraft should not be brought to a stand still. The system design had completly anticipated the will of the pilot. Unfortunately that wasn't what the pilots wanted. Once again. A machine cannot read one's mind.

This quote from camp A stalwart Dani would be truly funny if we werent discussing such a serious subject.Even if you make allowances for the "English",it just makes me cringe when I read it.You cannot command something unwittingly.The pilot forgot to retard the TL.Thats not a command.If the computer accepts an illogical command,then it is as stupid as the pilot.Is it not?He says the will of the pilot was to land on a short wet rwy with app thrust on #2.Really?The computer understood this,accepted it and gave him the hybrid state.Thats nice.

Wait just a second..it gets funnier.

Quote:
There is absolutely never ever the need for reverse on one engine and forward thrust on the other

Yes there is. Unintended reverser deployment. Mishandling of TL. Human error. Mechanical failure...
The system also anticipates this situation by adding the trust on the remaining engine.
Both cases are built in the system. It is fool proof. Believe me, those engineers spent a lot of time to go through all posibilities.

Lets break this down closely.
Unintentional reverser deployment?Theres a need for this is there?Please tell me.If a reverser deploys in flight(as in lauda),then theres been a serious mechanical failure..and we certainly dont need or want that do we now?
Mishandling of TL and /or human error?.Theres a need for this?I'd like to know when.Theres a need for an interlock mechanism that prevents human error/mishandling of TL's becoming a smoking wreck at the end of the runway.
Mechanical failure?Theres a need for mechanical failure is there???????
The system is "foolproof"..the engineers went through all the possibilities.Did they now?Tell that to the families of the 200 dead.

He saves his piece de resistance for the end...

but also if a Boeing doesn't give you reverse if you are not in idle, this doesn't help you in the TAM case.

This reveals neatly his lack of understanding of the value of an interlock mechanism and how this TAM crash happened.NO RETARDATION=NO SPEED DECAY+NO CONFUSING HYBRID STATE=TOGA.The pilot is human and subject to survival instinct.If that intuitive argument doesnt convince you,consider that the pilots were experienced and must have mentally prepared for the TOGA option if retardation didnt proceed as per normal.How can you go for TOGA after TR activation?They were trapped.

[bsieker]

Originally Posted by Rananim quoting from Boeing FCOM

The reverse thrust levers can be raised only when the forward thrust levers are in the closed position

As EMIT pointed out, this is not unambiguous.It can relate to all thrust levers together, or each one individually. (And to reassure you, the B737-800 FCOM uses the same wording.)

It could be read as: On each thrust lever, the reverse lever can be raised only if the forward thrust lever is in the closed position.

And the paragraph a few pages earlier about each engine having its individual control suggests just that.

This is essentially no different from Airbus.

It could also mean, less ambiguous: The reverse thrust levers can only be pulled when all forward thrust levers are in the closed position., which is the reading you prefer.

But did you actually try it, to see which of these readings is correct?

I'm on shaky ground here, since I can only reverse-engineer the workings from the FCOM and various reports, so it would be nice to have some Boeing pilot test it in the simulator and report back.

[edit]

The incident Lemurian mentioned (B747 overrun) indicates that there is no cross-engine mechanical interlock, otherwise the pilot either couldn't have gotten reverse if the one engine automatically went to Go-Around thrust, or the Engine could not have gone to Go-Around with at least one in Reverse.

Apparently there is only a per-engine interlock, which is not needed on Airbus, since Reverse and Forward thrust are commanded with the same lever. There is a latch that prevents accidentally going past IDLE in either direction.

[/edit]

Bernd

[bsieker]

Originally Posted by Lemurian

Please refer to the 744 incident in Tahiti, in which the handling pilot fought an automatic go-around, managed to land but then lost it when he couldn't bring all the reversers all together, leaving #1 to accelerate to full go-around forward thrust, while the other three were in full reverse thrust. Result was a visit to the coral reef.

Interesting. I could only find the french report at the BEA web site. Is there an English translation available?


Bernd

[bsieker]

Originally Posted by Rananim

Lets break this down closely.
Unintentional reverser deployment?Theres a need for this is there?

That's not what he said. He said there may be a need for reverse on one angine and forward thrust on another, in case of uncommanded reverser deployment.

Wouldn't you agree to that?

The problem lies somewhere else. There may never be the need to have one thrust lever at CL and one at reverse. Which is different from having differential (or opposed) thrust on the engines.

But from what I can see, it is not clear that any manufacturer keeps you from setting the levers in such a way.


Bernd

[FrequentSLF]

No pilot here

In various posts is indicated the the braking effect of full reverse (both operative) will be at the best 6%, 3% with one operative. From other posts I also understood that once the pilot has engaged the TR he has commited to landing, and TOGA is no more an option.
Is it worth to drop the TOGA option to achieve at the best a 3% additional braking effect?

Andrea

[PBL]

Originally Posted by FrequentSLF

Is it worth to drop the TOGA option to achieve at the best a 3% additional braking effect?

I am fairly sure it was pointed out some x-thousand posts ago that the proportion changes on a icy runway. Southwest went off the end of a snowy runway at Chicago Midway and killed a car passenger because deployment of reversers was significantly delayed over the assumed deployment time in their landing-distance calculation.

So they are good insurance for the weather. But these sliding-cowl 90+-degree thingies aren't as effective as good old clamshells, so I understand.

PBL

[Lemurian]

744 overrun @ Faa

bsieker,

Is there an english translation available ?

I haven't found any, except some very basic info from *aviation safety Network*.
If you're really interested, I could volunteer a translation, but this is an excerpt of the report :
At 21:05 the aircraft touched down at a speed of 168 knots. Two seconds later no. 1 engine power increased to 107% N1.
Because of this the spoilers did not deploy and the automatic brake disarmed. Reverse thrust was used on all remaining engines. Because of difficulties due to thrust asymmetry, the no. 4 engine thrust reverser was cancelled. The aircraft overran the runway and ended up in a lagoon.

Oh dear ! Even bloody moving T/Ls can't save the day when your chips are down ! This musrt be the end of the world !

[bsieker]

Originally Posted by Lemurian

If you're really interested, I could volunteer a translation, but this is an excerpt of the report

Yes, I found that, and I downloaded the French report from bea-fr.org.

Thanks for the offer, but I think my school French and an online dictionary will let me figure it out.

"système automatique de vol". What a beautiful language. (No sarcasm intended.)

Most important was the FDR graph, showing that N1 of no 1 engine went to "pleine poussée positive", and thrust reversers were deployed after that, which clearly shows: no inter-engine interlocks.


Bernd

[ChristiaanJ]

Lemurian,
Do you have a link for the French report?
Couldn't find it, but while looking found this one.
http://www.bea-fr.org/docspa/2000/tj...tj-b001105.htm
Sorry, also in French.

[flyingnewbie10]

The previous transcript of the voice recorder missed some time, perhaps the most dramatic one. The House of Representative Committee (CPI) heard the full tape recently, and after that they came to the conclusion that there was no HR in the disaster. They also learned that in the simulator the "retard" sign goes on until the TLs are in the right position while that in the TAM plane it stopped after repeating twice. Finally they said that there was the noise of the TLs being placed on Idle.

Marcio,

Maybe the difference between the simulator and the PR-MBK retard warning is due to some update that the simulator complies with.

However I am very curious about the sound of (both ?) TLs being brought to idle... Maybe there is some analysis already being made with the CVR to confirm it or not.

An Audio Spectrum Analysis ?