Indeed, barit1 is quite correct.
On large radial engines, the magneto checks are done at the ambient pressure (29 inches at sea level, approximately, less at higher altitudes) and the propellor feathering checks done at a lower power setting.
No harm done whatsoever.
I have always thought that the best propellor/power arrangement was on the first successful turbine engine in commercial service, the RR Dart series.
One lever (and an electric fuel trimmer) to set the power and RPM.
Good idea, then, even better now, even after all these years.
So what if it was a screamer during ground ops...airports are supposed to be noisey places...
