ORIGINAL: pe reivers
ORIGINAL: karolh
The difference that altitude and humidity makes is no stranger to me as I fly from two fields, one at sea level and the other at approx. 3,000', and the carbs require leaning at the lower altitude and richening at the higher one. Needless to say that at sea level the engine makes about 300 more rpm.
Karol
The fact that you gain 300 rpm means other factors than just altitude play a role here. All other things equal, rpm should be the same at sea level or at altitude.
I don't understand that statement PE. An engine loses approximately 3% power per each 1000 foot gain in density altitude. The thinner air the prop is spinning through does not compensate enough to counter the engine power loss. RPM's at altitude go down. At around 8000 feet, full power is only about 75% of what it would be at sea level and 59 degrees, (and 29.92 barometric pressure.) Unless you are in a full size airplane with a constant speed prop. Then you can set the rpms wherever you like by changing the pitch of the prop, up to a certain altitude...
AV8TOR