N2 seizure triggers FADEC thrust increase?
 

Hi all,

In case a flex takeoff is performed, resp. a takeoff with reduced thrust setting, a FADEC would command a higher thrust setting automatically in case it detects an engine failure.

What parameters are measured by a typical FADEC to detect an engine failure?
I know that the FADEC on the Embraer 135/145 would detect a flameout, but would it also detect an N2 seizure? I guess it would, but is there anyreason why it would not, perhaps?

Thanks.

This is very type specific isn't it? My 737 doesn't give me an more thrust in the N-1 case - and I'm happy it leaves that decision to me :}

The 737NG recognizes an engine failure (for the LGTU) by the N2 value, if that is below self-sustaining the LGTU will activate (among some other variables) - I suspect it could be similar for the Embraer? If so, a seizure will also trigger it...

I hate to see the word seizure used to describe engine failures.

Engines don't seize under Ram air conditions, they do however exhibit a rate of change in RPM over a few seconds but not to zero.

The safety related concept with FADECS and engine failure conditions has several parameters it can sense and compensate for.

e.g. Differences in N1 N2 against a standard or the other engine, and/or diffrences in EPR between engines against selected power conditions.

Flameout is also not a useful terms other than what N1, N2 and/or EPR are present.

Note the above comments apply to propulsive forces and not necessarily to damage conditions within the engine like vibration or excessive temperature. It all depends on what this question is really all about

There are obviously parameters in logic. An N2 failure would have a result on N1/EPR and EGT. I believe a thrust increase would be momentary at best "Full Authority Digital Control". The logic should be is N1/EPR and EGT within tolerance as N2 could be a loss of indication, follow procedure.

An N2 seizure would most likely be felt and certainly seen as a catastrophic indication. The FADEC response is irrelevant...

If you are performing a flex temp take-off you are spoofing a higher ambient temperature to trick the FADEC that the power available are a lot lower than what they actually are.

Stand the throttles up/in Flex/MCT anyway etc the engine will suddenly have the ACTUAL power available to it, getting you out of trouble; plus the flight crew will be at one engine out speed.

How this is read by the FADEC is based on many parameters. ENG FAIL msg is usually a command vs actual output in air mode. The procedure I presume would be to shut the engine down from the cut off switch defaulting CMD thrust on the good engine to MCT and ACTUAL Power Available.

Even with the ambient temperatures hot and high, the engine has an EGT margin that can be exceeded. How much you cook the engine depends on the situations.

N2 seizure?

Simple - No N2, no fuel pump rotation, no EGT. Fly the aeroplane. :)

Kind of tough to find a report of one with no EGT. :)

more like 1 out of 100 million hrs

Many thanks for your answers. Well, the scenario is as follows:

On the E145 you have two options to set thrust:
- Reduced thrust (ALT T/O-1)
- Maximum thrust (T/O-1)

If a takeoff in with reduced thrust is performed and an engine flames out, max thrust is automatically commanded by the FADEC. Alternatively it can be selected by advancing the thrust lever to the detent.

Interestingly, the simulator does not trigger max thrust in case of an N2 seizure. It only does it with e.g. a programmed flameout. What I wonder is, is this a bug in the software of would the real aircraft behave the same way?

The seizure programmed into the simulator is to train for a severe engine failure scenario (loss of N, High EGT, vibration accompanied by severe yaw).

The FADEC programming boost is unique to the aircraft installation and is power sensitive. The two are not necessarily the same unless the operator requests the training match the same scenario (The simulator programming matches whatever the training spec calls for).

It's not necessaily a bug in the programming, its just a missed opportunity

Even the SAS pilots didn't know that their MD80 engines would advance into an overboost when they ingested the hail since their training never accomodated that combination.

If the E145 is like other APR equipped planes, in the event of engine loss while operating a reduced thrust take-off, I think it only adds thrust equal to the delta that would have occurred at rated power. That is, if APR adds 5% to rated power, with a reduced setting, it only adds 5% to th existing thrust. If you want rated power, you would have to manually select APR.

Simply put, APR adds to the thrust set at the time of failure.
GF

It depends on the parameters sensed by the APR logic. Ones I have seen include CDP loss as part of the logic. If N2 seizes, CDP drops to ambient, and that (perhaps in combination with other sensed logic) will trigger APR.

But I don't know if E145 donks have this logic.