V1,reverser deployed,go or nogo

[kuobin]

V1,reverser deployed,go or nogo?:}
type:ERJ190.

[MD83FO]

what does the FCOM say?

[kuobin]

never been mationed.

[JeroenC]

Even after V1, if a *catastrophic* failure occurs, reject and go off the end (relatively) slowly. That being said, I would chop the power of the offending engine and go airborne.

[cosmo kramer]

That being said, I would chop the power of the offending engine and go airborne
What does the auto brake system do? Don't know you type, just asking and thought for consideration. For the 737, it is not described clearly what will happen if ONE thrust lever is retarded.

I would probably go airborne without touching anything and solve it in the air. Most likely it would be a faulty indication:
"Only multiple failures could allow the engine to go into reverse thrust."

If not:
"The EECs prevent power above idle if the related thrust reverser has moved from the stowed position."

I am just saying that if being to creative, you might be in for some suprises.

[Artie Fufkin]

Done it in the sim in a 737.

When thrust reverser deploys, the thrust lever auto-retards very quickly to idle on affected engine. Continue airborne.

[tdracer]

Artie


On the neo-classic 737 (heck, all the pre-FADEC Boeings), it is true that the throttle will auto-retard for uncommanded T/R deployment.


On FADEC, it's all done with electrons, the throttles won't move for uncommanded deployment. However an uncommanded stow can still move the throttle.


That being said, post Lauda, all Boeing airplanes have triple redundant systems to prevent uncommanded deployment. The likelihood of all three systems failing is way less than 1/billion hours (full up it's more like 1/trillion hours). Bum indication is orders of magnitude more likely.

[safelife]

Going on seems risky to me. If you're heavy single engine performance would give you little more than 2.4% climb gradient - and probably no climb at all with reverser doors open.
If you're light your V1 wouldn't be much higher than minimum control speeds, so a sudden reverser deployment would leave you off the runway sideways as soon as it happens.

[The Banjo]

FAR25,933 suggests that this scenario is part of the certification process:

(a) For turbojet reversing systems --

(1) Each system intended for ground operation only must be designed so that during any reversal in flight the engine will produce no more than flight idle thrust. In addition, it must be shown by analysis or test, or both, that --

(i) Each operable reverser can be restored to the forward thrust position; and

(ii) The airplane is capable of continued safe flight and landing under any possible position of the thrust reverser.

(2) Each system intended for inflight use must be designed so that no unsafe condition will result during normal operation of the system, or from any failure (or reasonably likely combination of failures) of the reversing system, under any anticipated condition of operation of the airplane including ground operation. Failure of structural elements need not be considered if the probability of this kind of failure is extremely remote.

(3) Each system must have means to prevent the engine from producing more than idle thrust when the reversing system malfunctions, except that it may produce any greater forward thrust that is shown to allow directional control to be maintained, with aerodynamic means alone, under the most critical reversing condition expected in operation.



[Amdt. 25-72, 55 FR 29784, July 20, 1990]

[JeroenC]

Cosmo, 737. Indeed good consideration.
I understand about statistics etc, however, the OP said "deployed", not just the light.
Didn't know the EECs would do the work for me;)

[172_driver]

Will it even get airborne? Artie suggested it works in the 737 sim. In any case your field- or obstacle limit performance must be heavily compromised?

I don't know how to quantify the extra drag but I have the feeling with an open reverser door it will be a lot. Perhaps tdracer knows if any such calculations have been made considering FAR25.933 mentioned below.

Aircraft unable or unsafe to fly, as a reason for the subsequent run-off and court hearing?

Considering the remoteness how many would even be able to distinguish an open TR door with a normal engine failure as the swing occurs close to or past V1. To make an informed split second decision.

[lomapaseo]

Don't get too wound up about comparing scenarios with Lauda. to support what ifs.

Lauda and a couple of others were in a climb condition and the ability to control sudden roll was affected by the unwanted reverser efflux over the wing.

At lower speeds associated with V1 the effect on control should be less and it's more akin to an engine out symptomatically.

I would much prefer the average pilot to perform by rote at V1 unless they have been specifically trained otherwise

[DevX]

kuobin Quote: V1,reverser deployed,go or nogo?


Which A/C, and why? :confused:

[odericko2000]

Tried it on a 767 sim, it's extremely dangerous getting airborne with a deployed reverser, out of all the scenarios we tried, only survived it by cutting of the engine as soon as is practicable, even at idle power on the affected engine, the roll was just uncontrollable. As someone has mentioned above, I personally would abort and take a risk of running off at the end of the Asphalt.

[MD83FO]

on the MD80 its go and its briefed before take off as a memory item with reverser deployed and positive yaw, fuel lever cutoff.
it takes full rudder and aileron until speed increases.

[cosmo kramer]

I should have been clearer in my post, that it applies to 737NG... But obviously the classic doesn't have EECs, so it should be clear anyway.

The 737 Classic doesn't retard to idle, and hence is probably equal in severity as the 767. My previous company operated both Classic and NG, and our emergency briefing also contained that only action below 400' would be to shut down the affected engine, in case of reverser unlock. Tried it in the sim once, maybe in 1 or 200 feet, and it was a non issue when prepared for it. I can imagine it would be different if it comes as a surprise.

That's the reason, I had this information in the back of my head, as I enquired about it, at my present airline. They don't see it necessary to be part of the briefing and the explanation I got, was that it is a non issue on the NG.

[tdracer]

I don't know how to quantify the extra drag but I have the feeling with an open reverser door it will be a lot. Perhaps tdracer knows if any such calculations have been made considering FAR25.933 mentioned below.Post Lauda, Boeing stopped showing direct compliance with FAR 25.933 (turns out that the methods of showing compliance were inadequate anyway). Instead, Boeing has used "ELOS" - Equivalent Level Of Safety - basically demonstrating that we comply with the intent of the rule but don't necessarily comply with the letter of the rule. The ELOS for 25.933 is to show that an uncommanded deployment would never happen ("never" in regulatory parlance is less than 10-9/hour (one per billion flight hours). So all the analysis related to 25.933 has been to show it can't happen - even with potential latent faults, inspection intervals, etc. (it's quite an involved analysis). So that's a long way of saying that 'no, the controllability analysis for a deployed reverser was not done'.

I was directly involved in the Lauda investigation so I know quite a lot about it. On the pre-FADEC engines, there is a mechanical linkage between the T/R and the throttle that if the reverser deploys with the throttle off idle in forward, it'll pull the throttle lever back to idle - sometimes called a 'throttle snatcher' (that's on Boeing, I assume the other guys have/had something similar). On FADEC, the control has sensors that determine the T/R position, and will retard thrust to idle if the reverser is not in the commanded position. What we discovered on Lauda was that the transient is the problem - the engine was at max Climb when the reverser deployed and by the time the engine had decelerated to idle they'd already lost control of the airplane. For a deployment at V1, I'm guessing the engine won't decel fast enough to avoid controllability issues as well. However I don't think the 'light' by itself would justify aborting - but reverser indication along with a sudden big yaw, I think aborting the takeoff would be in order at V1 (maybe even at V2) :uhoh:

Cosmo, I suspect the reason they told you it was a non-issue on the NG is that the cert basis is it'll never happen.

[172_driver]

tdracer,

Very informative, thank you!

[cosmo kramer]

The LTE I spoke with about the topic said that done in simulator, it is a non-event. And should be dealt with above 400 feet as any other malfunction. That the feeling was not much different than an normal engine failure.

He even offered me to try it out. Which meant to tag along with him, next time he went to sim, as I didn't have an upcoming check - so I declined and chose to take his word for it. I have since forgotten about it, and didn't try it out in the later checks. Had my last LOFT/LPC last week, so it will be a while before the opportunity is there again.

Perhaps if someone has an upcoming check, they could ask to try it out and report back?

[cosmo kramer]

I see I missed some replies before posting the last two posts, sorry for not being careful reading, Artie and tdracer.

Artie, you already tried it in sim. Was it NG or Classic? Did you do it at V1 or after being airborne? How violent was the yaw?

Also, what would be the reason that my old company required to include revs unlock in emergency briefing for Classic. The info I got in the old company was that it was only a severe problem on Classic. Why would it be more important to shut the engine down on Classic, than on NG? I can only imagine the reverser design differs that much to make a huge difference in idle thrust? Or the general performance of the remaining engine? Or that the idle function of the classic (not mentioned in the QRH btw) is slower reacting than the EECs?

We had that example mentioned above mandatory in a simulator session (reverser unlock in 1-200 feet). It's years ago, so my mind is not clear on the details. Didn't fly Classic for ages now (unfortunately, love it!). What I do remember is, as said, that it was a non issue, if immediate action was taken.

[underfire]

FAR25,933 suggests that this scenario is part of the certification process:

For once and all, stop with FAR and Cert quotes..it has NOTHING to do with reality. :mad:

[chimbu warrior]

I imagine it would have a lot to do with the type of reverser and type of aircraft

Blocker doors?
Buckets?
Sliding sleeve?
Wing or aft-mounted engines?

As was mentioned above in the MD-80 series apparently it is a go, but it is unwise to use procedures/practices from one type on a completely different aircraft.

[tdracer]

As chimbu notes, the configuration makes a huge difference. With wing mounted engines and fan cascades (e.g. Lauda), the reverser efflux effectively destroys nearly all the lift on that wing and it drops like a rock. Very, very difficult to control.
In the aftermath of Lauda, I was involved in some wind tunnel testing of a 'clean' wing with a reverser deployed. Before we started the test, the Aero S&C guy was arrogantly proclaiming that the scenario was readily controllable and he was willing to go on a flight test to prove it by deploying a reverser at max Climb power. As the testing proceeded and he started looking at the data, he started getting really quiet, and by the time we finished up 10 days later he wasn't saying much of anything. :sad:
Cosmo, when you say 'classic', is it safe to assume you're talking 737-3/4/500? To me the 737-100/200 is the true classic, although the people that work 737 tend to refer to the -3/4/5 as 'classic' and -1/2 as 'Jurassic' :E.
There was one crash of a 737-200 due to a T/R deployment - Cranbrook. During landing in a snowstorm, a snowplow appeared of the snow, they stowed the reversers and took off. Unfortunately one reverser didn't completely stow and lock before they took off - when air/ground removed hydraulic pressure after liftoff the aero forces caused the reverser to re-deploy at ~300 ft. and it was uncontrollable. Although the -200 had clamshell reversers, they were behind the wing - I doubt the -3/4/500 with fan cascades in front of the wing would be any better.
ASN Aircraft accident Boeing 737-275 C-FPWC Cranbrook Airport, BC (YXC) (http://aviation-safety.net/database/record.php?id=19780211-0)

I wouldn't put too much faith in the simulator responses to a T/R deployment during takeoff (or even during flight) - such a scenario is far too dangerous to test so it's all based on analysis. One of the things that came out of that post Lauda wind tunnel testing was that the simulator response to an in-flight deployment wasn't even close - reality was far worse than the simulator.

[JeroenC]

So, guys, what's the conclusion? Abort? Close throttle? Trust FADEC to do that for you? Shutdown engine? Do nothing and see when airborne?

[DevX]

QUOTE:Do nothing and see when airborne?

What a stunningly epic idea! :ugh: Ever thought you won't even make 'airborne', well not in the way you might be thinking!

Anyway, the OP is conspicuous by his absence.

[172_driver]

So, guys, what's the conclusion? Abort? Close throttle? Trust FADEC to do that for you? Shutdown engine? Do nothing and see when airborne?

After all, the cost vs. benefit analysis says it's a non-issue.. so don't worry :ok:

Seems like we are looking fir an answer to an ill-defined problem, obvious from this thread is none really knows how what will happen should it actually happen..

[lomapaseo]

Seems like we are looking fir an answer to an ill-defined problem, obvious from this thread is none really knows how what will happen should it actually happen..




are you suggesting that there is no aircraft performance analysis that can be done?

Clearly the driver responses are not predictable and that does put the situation in doubt

[172_driver]

are you suggesting that there is no aircraft performance analysis that can be done?

I am suggesting what tdracer wrote earlier: - So that's a long way of saying that 'no, the controllability analysis for a deployed reverser was not done

For Boeing that seems..

[lomapaseo]

I am suggesting what tdracer wrote earlier: - So that's a long way of saying that 'no, the controllability analysis for a deployed reverser was not done

For Boeing that seems..

Ok that's past tense. I am looking at today for the specific malfunction the OP set forth at V1 speed with all engines operating.

The N1 decay rate is known (FADEC chop), the efflux is known, the effect on the wing devices can be modeled along with the lift vs aircraft speed with variable rudder inputs.

What seems to be in question is the pilot inputs for braking, rudder or aerilons vs altitude

[tdracer]

The N1 decay rate is known (FADEC chop), the efflux is known, the effect on the wing devices can be modeled along with the lift vs aircraft speed with variable rudder inputs.All that stuff was done to certify the 767 and meet 25.933 pre-Lauda. They even did a flight test - IIRC at a steady 200 knots/20k and the engine at idle, they deployed the reverser and showed it was controllable.
What Lauda showed us is that the analysis was garbage - it didn't reflect the real world. Unless the engine was already at idle when the T/R deployed, the aircraft wasn't controllable. So, rather than try to figure out how to fly an uncontrollable airplane, the solution was to make sure it never happened again.

[Green Guard]

I am sorry, but this is kind of a stupid question.

One reverser deployed on any type of aircraft on V1 ( i.e. = TO Thrust)
even if you wish to go, you will go nowhere up, but only in the grass or on the runway, depending on a pilot.

[Artie Fufkin]

Cosmo, it was in the classic. Been given it several times in LPCs at V1 and in initial climb out.

The yaw was strong, requiring full rudder and some aileron to keep straight. The climb out performance was terrible, so bad that I shut the effected engine down below 400ft to get it climbing. This resulted in a bollocking from the back and a repeat. Second time we did climb. Just.

One joker gave it to me with left reverser deployed, 35 knot left crosswind and 50ft emergency turn. Wasn't pretty but it did work. Just.

I wouldn't like to experience it for real.

[Nubboy]

Not 737 I know, but if you want to see the results of putting power back onto an engine with a deployed reverser, try a search for TAM 402 31st October 1996.
Not nice, at all.

[kuobin]

Type is ERJ190.

[lomapaseo]

Again, Lauda doesn't enter into the OP original question. It was true that the original cert basis did not adequately cover that event and that it was later deemed that average pilot training could not accommodate a Lauda event in climb. (things happen too damn fast for the pilot to figure out the right controls).

However The KE A300-600 event did show that an exceptionally experienced pilot could recover a large twin at similar conditions by continuing the roll 360 degrees.

Since we don't count on exceptionally experienced crew the rule was modified as stated above.

However my arguments are confined to the knowledge we have today that suggest that an average pilot can safely accommodate a reverser deployment at V1 by continuing the takeoff. With knowledge of statistics I must say that this is the safer course of action.

I am even more concerned with comments that arrive at two different conclusions since to me it is clear that they are not both equal. I would be content if this question and decision making never came up in the first place since we appear not to have agreement and further discussion is sure to create even more confusion.

[172_driver]

I am even more concerned with comments that arrive at two different conclusions since to me it is clear that they are not both equal. I would be content if this question and decision making never came up in the first place since we appear not to have agreement and further discussion is sure to create even more confusion.

Who can with certainty draw any conclusions at all? There are testimonies in this thread that it's possible to continue based on sim experience. But the fidelity is questionable? Some real world examples (Lauda, Cranbrook), although not technically identical, suggest that it wasn't a good idea to attempt flying with an open TR. There is none that lived to tell the tale what happened at a post V1 thrust reverser deployment. Even if it is possible to continue in one type (say MD80, thrust close to C/L), the same may not be true if a TP went into Beta-range. No one size fits all.

I think the discussion has been very informative and even if I haven't made any absolute conclusions I have expanded my mind about such a scenario. I have also learnt about FAR25.933. My type have redundancies in place to not generally worry about TR deployment. Therefore no training is in place to manage such a thing.

[Centaurus]

....with the JT8Ds on the 727 with clamshells, this was not a gentle, gradual thrust lever movement....it was a relatively rapid, potentially knuckle pinching or palm bruising 'snatchback'.


Now that is interesting. I have experienced that on a 737-300 simulator when actuation on the instructor panel of uncommanded thrust reverser causes the selected thrust lever to snap back to idle instantaneously (one second) and is a real OH &S problem which could easily lead to a broken finger or crushed side of the hand. On other 737-300 simulators the closure rate is much slower.

Reminds me of similar OH&S concerns where you see the PNF "backing up" the thrust levers on take off in the 737 and then casually leaving their hand behind the thrust levers in the misguided impression this will prevent the thrust levers from sliding back if the PF takes their hand off them. If the PF makes a sudden decision to reject the take off run and snaps the thrust levers to idle, there is a good chance of the PNF being unable to get his hand out of the way and severely damage his hand trapped between the thrust lever idle position and the start levers just below.

I doubt if the PF will have the time to say to the PNF backing up the thrust levers, "I say old chap, I wonder if you mind removing your hand from behind my thrust levers as I would very much like to reject the take off right NOW:ok: