little engine test at cruise alt
 

Question.
You are on the way on 777 airliner at the top of ascendnig at FL370 and noticed raised vibrations level on one of the engines. No loud bang following, no vibrations to airframe... just increased vibe level indication.
Now, you want to do some test for the engine by decreasing thrust to 50% or 30% or even to idle, to see if problem still exists.
Is this safe to manipulate thrust while cruising on that flight level?
Or you sholud call emergency and descend first if you want to do it?

Is the vibration high enough to warrant getting out the QRH? If not leave it alone. A plane full of passengers isn't the place to start testing theories.

First of all, This is a Professional Pilot website, not a computer flightsim wannabe site.

But to answer your question, if the vibration is below a certain level, as depicted by your limitations section of your FCOM and QRH, you can consider the engine to operate normally. But reducing thrust for an instant will not change your speed at all.
If above this limit, you follow the QRH, which might tell you to reduce the thrust until vibration reduces within limits.

It takes several minutes by the way for speed to drop to Driftdown speed at cruising level, with an engine flamout. On B744, around 7 minutes at optimum cruising level. ( weight/fl dependant obviously).

Thanks
And apologies for dusturbing but it was important thing to me to know.

May I be so forward as to ask why?

How many of us Profi pilots have started out as wannabe simmers?
What a :mad: remark......:rolleyes:

I believe Icelanta's objection was not to simming itself, but to posting the question in a "non-sim" forum. That he phrased it somewhat inelegantly doesn't necessarily annul its validity.

Private argue. With a bet. I lost.

What would you do if afterwards it still exists?

If you don't know then don't do it