What constitutes Severe Damage?

[Idunno]

The scenario is an engine fail on take-off. Large turbo-fan engine.
No loud bangs/vibration, just loss of power.

You look at the engine instruments to assess the situation.

How would you conclude 'Severe Damage' from the N1 and N2 gauges alone?

[LME (GOD)]

I don't think that N1 N2 would be the ones to keep an eye on. If you've thrown a blade, the vibs and EGT will be going ballistic

[m&v]

As LME says the main parameters to establish poss'Severe'damge are the Eng VIB's,although a siezed rotor could be indicated with a zero N1/N2(on idle rpm at all)....:O

[Idunno]

Had this in the sim recently (yes another one).

The engine failed at V1. No appreciable bang or vibration that I could detect. No fire warn. Nothing obvious on the vibration gauges either.

The instructor pointed out later that the N1 was at zero and this was meant to signify severe damage (and the requirement for the full severe damage checklist).

During the event the N2 was rotating (windmilling?) and the fact that the N1 was at zero did not particularily bother me because at low speeds (around V2) I wasn't troubled by a low or even zero rotation on the fan...I felt that the fact that N2 was turning contraindicated a severely damaged engine.

So is a rotating N2, but zero N1, at V2 speed, absolutely always indicative of severe engine damage (in the absence of any other corroborating symptoms)?

What do you think?

[Blacksheep]

Silly me. I thought that a seized rotor was indicated by the trim change caused by the missing engine.

Now that I'm confused, can someone tell us what fuse pins are for? ;)

[Captain Stable]

Idunno, it might help people if you can tell us what engine/aircraft type this was, how many shafts, etc.?

[Tinstaafl]

N1 gauge failure? :}

[Idunno]

A320, CFM 56. Two rotors. No gauges...got ECAM!!

[Capt Claret]

Would not zero N1 or N2 in an air coupled engine indicate severe damage?

[mcdhu]

From Airbus FCOM under ENG 1(2) FAIL (3.02.70 P11)

'An engine flame-out may be recognized by a rapid decrease in EGT, N2, FF, followed by a decrease in N1.
Engine damage may be accompanied by:
- Loud noise,
- Significant increase in aircraft vibration and/or buffeting,
- Repeated or uncontrollable engine stalls,
- Associated abnormal indications such as hydraulic fluid loss, or no N2 indication.

A321 CFM 5B3P

Cheers,
mcdhu

[ft]

Couldn’t the idea be that if you lose the engine and one or more engine indications which should remain along with it, it is not your normal flame-out? Thus, it might be prudent to assume that something has gone wrong in a possibly drastic manner.

Not qualified to have an opinion, mind you. Just thinking out loud.

Cheers,
Fred

[Idunno]

Thanks mcdhu, thats exactly what I needed.

[idg]

Don't know about the CFM on the 320/1, but the V2500 series can certainly show amber XXs for N2 at slow airspeeds even though the rotor is still turning. In these circumstances the clue to an N2 siezure would be lack of hyd pressure as displayed on the HYD page or alternatively an amber HYD warning on the ECAM on the list of aftected systems.

These would also be the indications in the event of an engine rundown after an accessary gearbox drive failure, since the N2 tacho is driven by the gearbox along with all the other bits and pieces.

[Ivan Urge]

From a Boeing sim instructors point of view and from the recent airlines I have worked for, if a common garden variety flameout occurs (ie something turns off the fuel supply for some reason) it should obviously be considered an engine failure.

On the other hand if, quote " Fire is detected in the related engine; severe damage which may be associated with airframe vibration and/or abnormal engine indications has occured; or the engine has separated" then that is (in Boeing parlance) an "Engine Fire Severe Damage or Separation"

Put very simply, if you lost an engine because the N1 stopped, it would have been precipitated by a very short period of very severe vibration as it ground to a very painful halt. That is severe damage. Idunno, I would suggest that you did have a short period of vibration, you just missed the cues whilst trying to keep the machine under control. Not a criticism, it is just an observation from many hours in the sim.

If N1 or N2 stops (which it would do with quite significant vibration), if fire or overheat warning occurs, if airframe vibration occurs associated with loss of thrust or abnormal engine indications (which could be caused by accessory gearbox failure, loss of oil pressure, or loss of a blade somewhere, for example) , or your engine has departed your airframe then carry out the appropriate checklist that isn't an "engine failure checklist"

[lomapaseo]

I would caution against trying to read too much into what constitutes severe damage.

In the recently completed PSM+ICR study by the industry experts, there was already way too much subjectivity being applied by Boeing, Airbus, the various simulator manufacturers as well as individual training sylabus by the airlines themselves.

Since we don't want to compound this just keep it simple until you go through a simulator check with the updated data from this PSM+ICR study incorporated.

Just some food for thought

These large turbofans don't seize.

Most N1 losses are due to the loss of the pickup, the fan still turns and may vibrate.

Most severe engine failures in the simulator are programed to add in extra drag (actual engine failures rarely add in extra drag even with the fan not turning)

Most training utilizes the severe engine failure drill as a reasoning to secure the engine (not fit for further use) No problem here, but key cue is unabated vibration until secured.

I don't wish to encourage ignoring the FCM but I am only trying to abreviate intrpetations beyond what's written.

[Idunno]

Good points all.

I might just make one of my own to the instructors out there.

When performing a PC, is it fair to present your candidate with a condition that is not explicit in its symtoms? If you are required to see a Severe Damage Checklist carried out, would it not be better to present a clear Severe Damage failure and save the obscure debate on failure symptoms diagnosis for the LOFT exercise?