Thrust Lever Blocked In The Sim

[LEM]

Our instructors like to give the thrust lever blocked in the sim, for example after an intermediate level off in the climb.

That's in a 737 but the discussion applies to all twins.

Problem is they encourage "bringing the airplane home" with an N1 of 60% on one engine.

I strongly disagree with this interpretation.

They haven't understood the rules of the game.

On a twin, we MUST expect a major malfunction of an engine, and be able to FLY on the remaining engine, that means being able to maintain level flight at least 1500ft above the airport we are diverting to.

My objection is this: if the good engine fails, you won't be able to FLY with an N1 of only 60% (unless you are very very light, but you can't really know).

They try to use the assumption that you cannot have two major malfunctions, like two engine failures.
We can consider the blockage of the thrust lever as a major malfunction, they say, so we bring the airplane home because we assume the other engine will not fail.

Well, all this math is WRONG.

A little boring to explain, but very logycal:

- If you assume the major malfunction has already happened, the rule of the game is to land ASAP.
You cannot continue to climb and bring the airplane home.

- If you assume the blockage NOT to be a major malfunction, then you must assume the major malfunction can still happen afterwards.
And in this case also you cannot continue to climb and bring the airplane home, as if the good engine fails, the other one stuck at 60% will not be sufficient to guarantee a level flight capability over any airport.

Boring enough?

Well, my conclusion is: if this happens, ask yourself: "If the other engine fails, will I be able to FLY?"

If not sure, land ASAP, don't bring the airplane home!!

LEM

[catchup]

I totally agree. Even all systems are still supplied, the performance is single engine. And this means land asap.

regards

[alexban]

LEM : again your smart instructor,i guess.
Where did he put this case in the qrh? I think his ideea is against the qrh.
Is there a 'thrust lever jammed' check in the unnanunciated checklist,or elsewhere in the qrh?
I guess not,and I would put this case as engine limit/surge/stall where one of the conditions is 'no response to thrust lever movements' and at the end of this case says 'land at the nearest suitable airport'
I've checked the maintainance manual,the part refering to thrust lever removal from the piedestal,it has all the schematics,and I think there could be no chance of getting a lever jammed.
Is it possible in the sim?Or they say 'imagine the thrust lever is blocked..."?
Brgds...
Alex

[LEM]

It is indeed possible in the sim (BRU, FRA, Bremen....), and it's really impossible to move...

If Boeing has implemented this failure in their sims, probably it's also possible in the reality.

Problem is it is not well understood by everybody.

I remember a thread some time ago where the instructor encouraged landing with the engine running - stuck at 70%!!

[catchup]

I think there could be no chance of getting a lever jammed.

Excuse me I don't know the 737 (only 727), but why couldn't it happen?

regards

[Mad (Flt) Scientist]

As the first post notes, the probability maths behind the assumptions behind this training is fundamentally flawed.

There are numerous multiple failure cases which are not considered for certification as they are demonstrated to be extremely improbable. Say rudder jam plus single engine failure, or multiple independent cause engine failures.

But once some of the events have happened, it is no longer extremely improbable that the remaining events will happen; all that is left is the residual probability of the remaining circumstances.

So if engine failure is 10e-5 and throttle jam is 10e-5, then combined failure is 10e-10 prior to departure - a perfectly acceptable probability for an assumed catastrophic top event.

But once one or other has occurred, all that is left is the residual 10e-5. No longer adequate for the top event, indicating that immediate action to mitigate the elevated risk is prudent.

Never mind the fact that you might be looking at a common cause scenario: what if the lever jammed due to FOD? How likely is it that there was FOD close to the second lever also, in which case there may be increased risk of a dual jam.

[alexban]

Even if there is a chance of jamming one thrust lever,where would you fit this in the QRH?
As I see it,this a case where you can not adjust any more the thrust on one engine,right? So ,quite similar with no engine response at thrust lever movement.In both cases ,with or without lever movement you'll have N1 stuck at some %.
This case (no response to thrust lever movement) is in the QRH, as opposed to lever jammed (which is not) ,and the indication there is land asap.

[lomapaseo]

I agree about the basics of the standard sim check without this added what-if

However it is not entirely unlikely (about 2 a year) that one of you will get a somewhat similar event when taking off into a flock of birds which completely knocks out one engine and damages the second.

So you clean up start to comeback. With the second engine damaged you find that you can't get more than 60-70% out of it without sending the EGT into the red or causing it to surge. Obviously you aren't going to shut it down to idle so you set it to achieve its max safe thrust and fly the airplane leaving that engine alone as long as you can in case you should stuff it up.

OK, also not entirely unlikely (about 1 a year) the fuel control (not the thrust lever) gets a bit of dirt stuck in one of its valves and locks it up at 60% without any control by the pilot except the fuel shutoff.

Now I'm not pushing to include these rare scenarios in your simulation training, but I would like you to consider whether you feel you are ready to handle such an event based on your current state of training?

[LEM]

Hi lomopaseo.
The scenario is not difficult at all.
What is interesting to discuss are basically two decisions:

1) Are we going to shutdown the engine before the approach, or are we going to land with the engine running?

2)Are we going to continue our flight back home or are we going to land ASAP?

The first point has been discussed in this (http://www.pprune.org/forums/showthread.php?s=&threadid=98254&highlight=B733+stuck+thrust+lever+sim+scenario) thread.

In this one I'd like to express my disagreement with those who encourage continuing the flight if this happens after takeoff with a thrust setting insufficient to guarantee a level flight capability should the other engine fail.

So once again, technically speaking this can happen and it is indeed feasible in the sim.
Just shut the engine down before the approach.
Easy.

But don't be tempted to decide for a landing with the engine running, or bringing the airplane home since "the engine is working and is producing electricity, hyd power...", hot water and whatever.

[flash8]

Date: 11/24/1992
Location: Liutang, Guangxi, China
Airline: China Southern Airlines
Aircraft: Boeing 737-300
Registration: B-2523
Fatalities/No. Aboard: 141:141
Details: The aircraft crashed into a 7,000 ft. mountain, 15 miles from the airport while on apporach. Malfunction of the thrust lever which caused a loss of control of the aircraft.

The aircraft crashed while on approach to runway 36 after the no.2 throttle became stuck in the flight-idle position. Mechanical failure.

Heres your answer guys.

[catchup]

Remember a tarom A310 with a frozen thrust lever crashed after T/O.

Somewhere in the 90s.

regards

[lomapaseo]

Both the 737 and the A310 incident were controlable by the pilot. Unfortunately in both cases he forgot to monitor the aircraft and take over from the autothrottle function which doesn't work well in asymetric thrust situations.

[alexban]

catchup: about the 310 ,as much as I know,it was not a frozen lever.
It was a malfunction of the autothrust coupled with a capt incapacity(heart attack or similar),and probable misreading of the eadi by the f/o,while in low alt turn ,in clouds,just after take-off,with a failed autothrust which increased one engine thrust while decreasing the other one,unfortunately the one inside the turn.
The f/o was an experienced pilot,but new on bus,just came from russian type airplanes.On those planes the artificial horizons works opposite than the western ones (the airplane simbol is turning,while the horizon is fixed).
So ,a chance to increase bank,when you actually try to decrease it.:( May them rest in peace.
flash8:i stand corrected.So,it is possible to stuck a lever.I don't know about this case,but i suspect the crash was a CFIT case.

[FlightDetent]

I am sorry to say, but I have always been puzzled by the loss of thrust NNC item of putting the start lever to idle and wait for EGT decreasing... We have used this only for dual ENG fail scenario. I do not have a QRH at hand these days, but does it not say in smaller print loss of thrust or no throttle response ? Hence I figured you can perhaps get caught at 1500 AAL with one ENG locked at R-TO N1, or have a thrust lever stuck. And recall item C/L applies for variety of scenarios. In some, it makes sense, start lever idle, wait for EGT decreasing.

LEM, is this not the NNC one shall use? I dunno. One would be killing a good engine and your paradox of the other one going totally apepoo still stands. Precisely as you say there is but one way to reduce exposure to the risk. My view.

[411A]

Stuck thrust levers are never a good scenario.
I have had only one, in a TriStar, and it stuck fast during descent.
Landed without incident, after having shut down the affected engine, and the maintenance rep lubed the pepper box.
Yes, it worked then, but later on it stuck fast again in the cruise (with another crew) and they had to land and get if fixed properly...which took three days.

The 250 pax were not happy campers, as was the respective airline's maintenance director.

Fix it right...the first time.:}

[prop jocket]

CATCHUP: 737 thrust levers can and do jam. This is due (According to Mr. Boeing) to the thrust levers, spoiler selector, flap lever and trim wheel all being mounted on what is for all intents and purposes a common shaft. We had just such an incident about three years ago (on the ground fortunately - the lever wouldn't advance much above flight idle), and the only way to clear the problem to disassemble things and fix what had gone wrong was to manually wind the trim wheel whilst heaving on the stuck throttle lever.

Wouldn't like to try that in flight.

[Charles Darwin]

Although this may be a very distant possibility on the 737, it can happen. IMHO the more problems you tackle the better you get go know the aircraft you fly. With my company we use the spare sim time after LOFT to do all sorts of silly things. Manual reversion, gear down, flaps 15, one engine inop, max crosswind, and the runway behind me in a tight valley, is on the top of the list of amusing sim rides. This is not, and may not be a part of the test, BUT it certainly is fun and feels good after a successful landing.

Remember; What has never happened can always happen again! :ok:

[SIDSTAR]

The engine of the 737-200, the JT8D had a particular failure mode where if you lsot the N2 (I think?) governor the engine would automatically run to 70% N2. As this was way too high for a normal two-engined approach you ended up shutting down the engine (as late as possible of course).