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?