V1,reverser deployed,go or nogo

[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.

[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.
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' .
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)

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! 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

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