Autodidact
Well-Known Member
Raymer's little book has a chart that depicts propeller efficiency at different airspeeds. I think I remember that larger, slower turning props were most efficient at the lower airspeeds, and that smaller props were also efficient, but at higher airspeeds.
If you have a 5000 rpm engine with a PSRU, you can conceivably make the prop turn at almost any rpm you want, from 1200 rpm up to 3600 rpm and more. Aside from physical restraints, like ground clearance or fuselage cross section, are there any advantages aside from propeller efficiency to gearing the engine for big prop over small prop or vice versa? Is this just a simple climb rate vs top speed trade off?
If you have a 5000 rpm engine with a PSRU, you can conceivably make the prop turn at almost any rpm you want, from 1200 rpm up to 3600 rpm and more. Aside from physical restraints, like ground clearance or fuselage cross section, are there any advantages aside from propeller efficiency to gearing the engine for big prop over small prop or vice versa? Is this just a simple climb rate vs top speed trade off?
