I can't speak specifically for the 'coupe because I own manuals only for my Alon. However, I think it's reasonable to to believe that at the RPM settings appropriate for your engines, the results are the same. Also, we need to agree that the percentage of available power (referred to sea-level at standard ISA conditions) at various altitudes for all non-turbocharged engines varies the same way. This is true because the amount of available power is proportional to the air density, which decreases with altitude. Actual power for a fixed pitch prop varies with RPM - at takeoff you do not develop 100% power because your static RPM is way below the RPM for rated power (check your engine nameplate).
I have two manuals, an "Approved Flight Manual... British Civil Airworthiness... prepared by Alon...," and the US version, also by Alon. They differ slightly, due to each countries' requirements. The US manual states "NORMAL CLIMB and MAXIMUM PERFORMANCE CLIMB - Mixture Rich (unless engine is rough; lean as required)." In another chapter it states: "CARBURETOR MIXTURE CONTROL - At altitudes above 5000 feet, the decreased air density may cause the mixture to become too rich for best power... The mixture should always be leaned during cruising operations at 75% power or less, but during climb only at altitudes above 5000 feet..." The manual also has a chart that shows "68% at 2350 RPM, and 78% at 2475 RPM at 4000 feet -- 77% at 2475 RPM at 6000 feet." A note below reminds pilots that the table is for "standard conditions." Under more extreme conditions, it is prudent to make adjustments to the above data. For instance, if temperature is extremely cold, the air may be so dense that you must lean at sea level in order to make the engine run smoothly - this is common practice in Alaska. A lot has been learned about engine operation since the 60's when my manuals were written. It is now also common to lean during a descent to keep the engine as warm as possible, richening the mixture only if a go-around is necessary - this also keeps the carb heat air warmer and prevents sparkplug fouling. It is also considered good practice to lean on the ground to help prevent lead fouling when using 100LL. David N6359V [EMAIL PROTECTED] wrote: > > [EMAIL PROTECTED] wrote: > > > > I've got a problem here. I've always been told that 8000 ft asl was the > > magic number above which you can't generate above 75% power. > > 3% per 1000 ft. power loss. Yet, here I'm hearing much lower figures. > > Which is it? If it ain't 8000 ft., I've been living a lie all these > > years. > > I'm interested in this answer, too. The number I had heard was that at > 7,500 ft msl, the engine couldn't develop over 75% power at max > throttle. > > Anyone have a formula for us? > > -- > Ed Burkhead > Peoria, Ill. > Ercoupe N3802H, 415-D > > --------------------------------- > to unsubscribe send mailto:[EMAIL PROTECTED] > > _____________________________________________________________ > Check out the new and improved Topica site! > http://www.topica.com/t/13 --------------------------------- to unsubscribe send mailto:[EMAIL PROTECTED] _____________________________________________________________ Check out the new and improved Topica site! http://www.topica.com/t/13
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