Engine fail scenarios

[Multia1]

Hi

In what situations would you treat a in flight engine fail as severe? Vibrations/fire for sure but if you dont feel it/ have no fire and your indications are:

1. Only N1 zero
vs
2. N1 and N2 zero
vs
3. only N2 zero

How would you analyse these 3 scenarios and when would you try to restart the engine?

[tdracer]

If you see "zero" rotor speed for any shaft - that suggests an engine seizure - at any flyable airspeed there should be a finite and measurable windmill rotor speed. Short of an all engine out emergency, attempting a restart would be a non-starter (excuse the pun :E).

[Atlas Shrugged]

Firstly, how many engines have I got... two, three or four?

[lomapaseo]

The great majority of N1 shaft zero indications are not seizures but loss of signal integrity. Windmill loads are quite significant on this rotor system

The n2 loss of speed do signal a significant loss of ability to restart.

Continued vibration with loss of rotor speed is significant that the engine is toast

add in other indications like fire or or EGT increasing and it's time to give up on the engine

[tdracer]

The great majority of N1 shaft zero indications are not seizures but loss of signal integrity. Windmill loads are quite significant on this rotor system

But, you just associated that loss of N1 indication with an engine failure. Since I don't think any engine control requires a valid N1 indication to keep the engine running, you're talking two independent failures if it's not a seized rotor (or other major N1 rotor damage). Most FADEC systems will even keep running without an N2 indication (using a synthesized N2) - a hydromechanical control may not keep it running without N2 - but if that's the case a restart would be impossible regardless.
Unless you're in an all engine out emergency, attempting to a restart with a zero speed rotor indication is asking for more trouble than you already have.

[president]

I would suggest that for that to happen you will have vibration at some point during the event. Neither rotor can go from crazy high RPM to zero without you feeling it. If you don’t you are probably sitting in an old simulator not capable of producing vibration.

Finally if any of the rotors aren’t spinning you won’t get a restart at all.

[safetypee]

Multia1,
The context of the situation should be reconsidered, use an alternative viewpoint before considering an option to restart the engine.
Are you attempting to word-match the abnormal procedure (descriptive advice) with the situation. SOPs cannot cover all eventualities.
Is the concern about any difference between highly reliable engine indications or the consequences of restarting with an indicated failure.

Is the aircraft flyable; if so fly it. If not consider restarting according to the need for thrust; there are very few scenarios where an aircraft will be unable to fly with a single engine failure. Don’t invent too many contributions in considering a mental ‘what if’ course of action. The training task should focus on how to think, not what to think.

Is the engine producing the required / expected thrust; check EGT/EPR in conjunction with rotor speed, aircraft yaw / roll motion. Are the engine ancillary systems working; elect generator, hydraulic pump, air supply; do you know which shaft drives them.
What was the history of the event, the preceding indications of engine / system operation; fluctuating or sudden change. Etc.

[Capt Fathom]

In what situations would you treat a in flight engine fail as severe?



How much does it scare you?

[sonicbum]

Hi

In what situations would you treat a in flight engine fail as severe? Vibrations/fire for sure but if you dont feel it/ have no fire and your indications are:

1. Only N1 zero
vs
2. N1 and N2 zero
vs
3. only N2 zero

How would you analyse these 3 scenarios and when would you try to restart the engine?

Cruise time reading : Handling Engine Malfunctions (http://www.smartcockpit.com/docs/Handling_Engine_Malfunctions.pdf)

[Jonty]

Hi

In what situations would you treat a in flight engine fail as severe? Vibrations/fire for sure but if you dont feel it/ have no fire and your indications are:

1. Only N1 zero
vs
2. N1 and N2 zero
vs
3. only N2 zero

How would you analyse these 3 scenarios and when would you try to restart the engine?


Personally I wouldn’t try and restart the engine in any of those scenarios unless I had a very good reason to.
Engines don’t just fail, they fail for a reason. So unless I had a very good reason to attemp a restart I wouldn’t.
Think long and hard about the consequences of restarting.

[FE Hoppy]

In the dim and distant past I flew a 4 engine type where we frequently shut down 1 and occasionally 2 engines to save fuel. we also relit them mostly. If a rotor isn't turning when you have airspeed, throwing fuel and a spark in it doesn't help.
If an engine has failed then it did so for a reason. If the FADEC has an auto relight function that didn't work when the rotors were still spinning quickly then you have no chance of starting it from 0.

Having said that, when the last one fails do what you can and good luck to you.

[Capt Quentin McHale]

Multia1,

I'm with safetypee and Jonty on this one. The first thing I would do is confirm that the engine is in fact failed/stopped by checking the engines other parameters (EGT, EPR, fuel flow/pressure, oil pressure/quantity, hydraulic pressure, electrics etc) and compare with other operating engine/s, then slowly retard the thrust lever to idle and monitor that engines parameters and see if they follow the thrust lever movement back to idle readings. Then, if in fact they do follow thrust lever movement, I would slowly advance the thrust lever and see if they follow thrust lever movement back up to match the other engine/s parameters. At least if the suspect engine's other parameters follow thrust lever movement, (without vibration/fire warnings) you would more than likely have an inoperable N1/N2 indication.

Rgds McHale.