Classic British Flight Sim

Archer wrote: it is simply the aerodynamics of the props which dictate 'normal' RPMs.

Well, not always. There were a number of American flat configuration engines which had critical vibration periods to be avoided, lest the crankshaft fracture, and this was another factor governing useable rpm in the cruise. Also, economy considerations often govern the use of rather lower rpm and slightly higher boost than normal 75% power figures , best economy ( or strictly speaking specific fuel consumption) being obtained at the maximum bmep setting . There were also some engines ( the flat 8s in the Beechcraft 80 were a notable example ) where it was necessary nearing the end of the cruise to step the power combinations down progressively so as to avoid thermal shock at descent power which otherwise shortened engine life considerably . These are all reasons why the latter day piston engines were so much more testing to operate than "point and squirt" fanjets,where really only startup had critical limitations , even though the latter were much more expensive