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V1,reverser deployed,go or nogo

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V1,reverser deployed,go or nogo

Old 16th Apr 2014, 01:16
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V1,reverser deployed,go or nogo

V1,reverser deployed,go or nogo?
typeRJ190.

Last edited by kuobin; 17th Apr 2014 at 23:13.
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Old 16th Apr 2014, 01:55
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what does the FCOM say?
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Old 16th Apr 2014, 02:36
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never been mationed.
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Old 16th Apr 2014, 03:22
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V1,reverser deployed,go or nogo

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.
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Old 16th Apr 2014, 03:49
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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.
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Old 16th Apr 2014, 04:18
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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.
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Old 16th Apr 2014, 04:34
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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.
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Old 16th Apr 2014, 05:30
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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.
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Old 16th Apr 2014, 06:26
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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]
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Old 16th Apr 2014, 11:58
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V1,reverser deployed,go or nogo

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
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Old 16th Apr 2014, 13:06
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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.
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Old 16th Apr 2014, 14:07
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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
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Old 16th Apr 2014, 14:10
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kuobin Quote: V1,reverser deployed,go or nogo?


Which A/C, and why?
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Old 16th Apr 2014, 14:34
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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.
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Old 16th Apr 2014, 16:51
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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.

Last edited by MD83FO; 16th Apr 2014 at 18:44.
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Old 16th Apr 2014, 17:58
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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.
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Old 16th Apr 2014, 19:32
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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)

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.
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Old 16th Apr 2014, 21:50
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tdracer,

Very informative, thank you!
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Old 16th Apr 2014, 22:08
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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?
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Old 16th Apr 2014, 22:20
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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.
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