The Murphy Builders Site

Steve, Hank ...

Here are some numbers with the O-320 / Prince 74x47:
Static RPM (tail tied down) 2,500
Rate of climb at 1,800 pounds gross from climb test report 755 fpm
(Pressure altitude 920 ft)
Cruise speed (two people, weight about 1,550; 2,400 RPM) 103 to 105
mph CAS
Max RPM at cruise >2,700
Max rate climb speed Vy is quite a bit higher than the manual says - 80-85
mph CAS versus 69 at 1,650 pounds

The fact that the engine will over-rev in cruise and the cruise speed is
low, definitely suggests too fine a pitch. You don't need 2,500 rpm on
take off either. I am starting to think that I have a lot of cowling /
cooling drag, although temps are very good.

Mike A / C-FNBO





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