Originally Posted by
Check Airman
Why’s full power harder on the engine at a standstill?
Inlets don't work particularly well without some forward airspeed. As a result, when sitting still, it doesn't take much of a crosswind (or worse, tailwind) to cause the inlet to start to separate when at high power - and a separated inlet can easily lead to an engine stall or surge (which are really hard on the engine). You're also more apt to suck up FOD when sitting statically than with some forward speed.
Back pre-FADEC, it was necessary to run the engines to takeoff power to check for proper operation of the bleeds and vanes - often requiring 'trim' adjustments to the hydromechanical control. At one time, I was involved in the engine run functional test requirements and would sometimes sit in for the engine runs. They'd always try to position the aircraft into the wind before the run, but that wasn't always practical - the engine run guys had developed a finely tuned ear to listen for inlet separation during the runs when the winds were less than favorable. Originally I was skeptical that you could actually hear the inlet separate with all the noise and vibration of an engine at takeoff - but then I was sitting in on an engine run and I started to hear this unusually growling noise - I was just about to say something like 'what's that' when the engine run guy snapped the throttle to idle - I'd just heard inlet separation...