> -----Original Message----- > Regarding C85, C90, and O200 engines, the horsepower > developed by each appears to be produced by going to > successively higher RPM, not as a result of more torque. So,
The C-90 developes 90 HP at 2475. The 85 is rated at 2575. This is why the 90 uses the 52 inch pitch while the 85 uses the 48 inch pitch. Your aircraft was certified with a particular prop/engine combination and static RPM limits. If the pitch you're using does not meet the static rpm limits, then the plane is technically not airworthy. I doubt if a C90 with a 7148 will pass. 50 inch pitch is a climb prop for a C-90 and 54 is cruise. The O-200 is a different beast. It is not, as far as I know, approved for use with the 71 inch (McCauley) prop. The 69 inch Sensenich (sp?) is approved, and due to it's smaller diameter, the pitch is higher than the 71 used on the C-85, even though the RPM range is also higher (2775 redline). > at cruise). The C90 is actually rated at 95HP at 2625RPM for > takeoff, but without a really fine pitch prop (or a constant > speed prop - wouldn't that be nice?), you can't develop that > RPM so you can't develop 100% power. > There is no legal fixed pitch prop that will allow 2625 in climb. You'd be cruising at something like 40% power at redline. 2625 RPM was only approved with either the Beech or Aeromatic props. John
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