ENG FAIL, is ENG damaged or not?

[anchorriver]

Just curious what sort of indication in N1/2 would tell you if a failed ENG in-flight is damaged or not. I am talking about GE CF6-80 engine, specifically. During the SIM I was told blank N1,2 indication, as well as N2 showing 0% are the sign of internal failure. I'd be grateful if you can share your experiences with me. Thanks in advance for your time and knowledge. Safe flight.

AR

[lomapaseo]

Don't rely on one parameter for a judgement.

The engine spools N1, N2 and N3 will windmill in flight at speeds sufficient to display RPM on the gages.

If you want to know if an engine is sick enough to be considered on deaths door look at EGT if its going up through the roof then that means there is no useful work being done and you better shut the fuel off.

The RPM loss to zero is typically a speed pickup/transducer failure and often associated with major fan damage associated with felt vibration in your seat and EGT through the roof. Damage in the high spool may or may not be felt as vibration, but EGT through the roof not responding to thottle retardation signifies major damage in this rotor.

note: the above is not meant to substitute for your training for a specfic installation and is only meant to help you understand what's likley going on in a failing engine.

[kijangnim]

Greetings,

Blanked N1 or N2 or N1 or N2 equal to ZERO, OIL pressure ZERO or close to, OIL quantity equal to ZERO, VIBs, you need a combination of a minimum of two of these to be certain that you have an engine damage, in any case if it happens in real life you will know it for sure.:E

Engine Failure is strainght froward the engine is windmilling in other words the all parameters are at a very low idle :ok:

[N1 Vibes]

anchorriver,

you can havea number of indications - those described so far are normally accompanied with a loud noise - either the enigne disintegrating, or the pax going "Whooooooooo" as the sparks emit from the tailpipe!

You can also have an engine failure without all the excitement, like a total oil loss, then engine grinds to a halt or you select HP to cutoff.

You could have continued surges. You could have acrid smell in cabin. All manner of things really. Quite often our pilots note bang and yaw, and are already correcting the yaw before they've got an idea of what the enigne is doing - and of course this is the right thing to do - fly straight and level - then put the sick engine out of it's misery.

As a previous poster put "you'll know"!

Best Regards and Safe Flying,

N1 Vibes

[BigJoeRice]

"As a previous poster put "you'll know"!"

Trying to sleep down the back on an empty night ferry flight to Jeddah; flash - almighty bang - attention getting vibration. Oh yes I knew alright. Couple of flight attendants came looking for me with an urgent message from the Captain to join him on the flight deck. Back in Algiers, big surprise (not) nothing but Taconite pellets in the tailpipe of Number 4.

[theWings]

Hi anchordriver,

I'm guessing from your question that your concern is as not so much how you'll know whether an engine has failed (all of the above are correct when they say "you'll know"!) as how you'll know whether the engine is damaged. And the reason for your concern, I am also guessing, is to do with knowing what to do once the failed engine is secure (i.e. after you've identified the failed engine, confirmed this with at least two parameters and then been through the appropriate recall items and checklists), because checklists, and we live or die by them, treat an engine failure differently from an engine fire, severe damage or separation in one important respect: do you attempt a restart or not? So, assuming it's not been on fire, you are looking for something that indicates whether the engine has been damaged (or dropped off!). I would suggest the following to start with:

-Engine vibration, felt or indicated
-Below minimum engine oil quantity
-Zero core or fan speed (especially if one but not the other)
-Visual confirmation from flightdeck or cabin
-Alerting System message implying damage

the Wings

[whatbolt]

At least when theres bits with part numbers on in the jet pipe you know its not a well engine.

[Piltdown Man]

I'm not trying to be horrible, but don't confuse the sim. with reality. If those giving you marks out of ten, say X, agree with them and act accordingly. Don't enter into any debate as they have all the big cards.

As it happens in this case, a windmilling jet engine in flight should have some indictation of shaft rotation. So in this case I'd agree and people far more eloquent than myself have explained why.

PM

[anchorriver]

You guys are awesome. I learned a lot. theWings, you guessed right, sir. I was wondering what indications would justify me to restart a failed ENG in flight. Now, thanks to you all, I have much better understanding. Safe flight, folks. I love PPRUNE Tech Log!

AR

[N1 Vibes]

AR

now that I see wher you were coming from - the do I/do I not relight the engine angle. I would go with the Wings outlined mental checklist.

Have personally experienced 2 engines out on an A330 during a test flight - #1 was a turbine overheat (cooling air overheat) indication, in simulated single eng climb, with #2 at idle. Then when we shut down the #1 (per the FCOM) and advanced the throttle on #2 - BANG - the engine surged and ran down to sub idle, it had flamed out.

As the riding engineer on the test flight, and an engine wallah. The 2 ex-Empire Test Pilots in the left and right hand seat turned round and asked "Which enigne do you think we should relight?", as they asked this question there was a thud and whirr as the RAT dropped out to give hyd pressure, this does tend to focus the mind somewhat!

We decided to relight the #1, as we only needed low thrust to return to HKG, and the overheat indication only came at CLB thrust. We obviously made it back safe.

When we got back on the ground we found that the #2 surge had only been an airflow issue, no physical damage had occured in the compressor, but because the enigne had rundown to sub-idle, in-flight - do I/don't I relight it logic suggested it could be damaged. But, it's all about what you observe/feel at the time.

I hope this is a good example for you.

Safe Flying,

N1 Vibes

[anchorriver]

N1 Vibes,

Thanks for sharing the good example with us. As I type this reply, I am sitting right in front of the cockpit poster, imagining what indications you had at the time. Great LOFT scenario...

AR

[Tee Emm]

CFM 56 engine. Would an auxiliary drive shaft failure (causing flame-out due fuel exhaustion) and N2 indicating zero, be considered as "Severe Damage" as far as QRH actions are concerned?

If the auxilliary drive shaft fails, does that mean that bits of the drive shaft are flailing about and maybe causing serious damage to nearby components?

[lomapaseo]

If the auxilliary drive shaft fails, does that mean that bits of the drive shaft are flailing about and maybe causing serious damage to nearby components?

The "serious" damage that is covered in the training relates to issues directly affecting safety of flight and are not related to economic issues or cascading effects internal to the engine.

Experience has shown

In a massive engine failure like disk rupture, case rupture, turbine shaft fracture, the serious safety related damage is all over by the time your eyes glance at the engine gages. The concern at this point is fire and that's about all the control that you have on it from the cockpit. even shutdown it will continue to windmill and possibly set up felt vibrations, but this is not of concern structurally to the aircraft since the design of the aircraft can accomodate this.

Many engine failures (including flame outs) can be restarted and at least operated at idle (generators, hydraulics). However, I would hestitate to run one that manifests vibration associated with other symptoms of failure.

It's easy to be cautious about an engine failure if you still have aircraft performance margin, but if you're in a tight situation you probably can continue a sick engine at idle (if no vibration) without the worry of catastrophic failure.

[Admiral346]

I peronally take any engine failure as a non-normal system behaviour.
I would not restart unless I have the other one quit on me also...
You don't know, what you will get yourself into, and the few indications we have in the cockpit hardly give a way to diagnose (unless it quits with a loud bang, EGT overlimit, or the like).

It is tought differently at my company though, and for the sim sessions I recommend to do it as your instructor says you should. Make up your own mind, once it is your but in the aircraft, not the instructors...

Nic

[lomapaseo]

I peronally take any engine failure as a non-normal system behaviour.
I would not restart unless I have the other one quit on me also...

Your choice:hmm:

however for the circumstances do consider the availability of a suitable restart envelop

[kijangnim]

Greetings
most of new generation FADEC will automatically attempt to restart the engine, so if it fails to restart and the cause of the failure is not identified, it is wise not to attempt a restart unless the other engine...
however we can consider that data have been automatically transfered via ACARs to your maintenance center, give them a SAT COM call (if so equipped) and ask them ... :ok:

[Tee Emm]

and for the sim sessions I recommend to do it as your instructor says you should.

It is certainly comforting to have such blind faith in your simulator instructor. If you are saying do as you are told just because the instructor says so and you need to keep on the good side of him, then fair enough in your advice. That is entirely different from receiving accurate technical advice.

On the other hand believe it or not, simulator instructors come in all shapes and sizes and some are very knowledgeable while others are ... not.

[NSEU]

Interestingly, the ENG X FAIL Caution message uses the following logic...

N2 less than 50% (sub idle) AND oil pressure less than 10psi AND Fuel Control Switch ON AND GCB open AND airplane in air mode.

I would have thought a windmilling engine would have kept the oil pressure above 10 psi???

Rgds
NSEU