altitude and rpms

jokaj

Seaman
Joined
Sep 23, 2008
Messages
73
Is there a general rule as to how much RPMs decrease per 1000 ft? I read a lot about loss of RPMs but no one has placed a numerical value to it. Thanks

joe
 

hwsiii

Commander
Joined
Jan 25, 2009
Messages
2,639
Re: altitude and rpms

Jokaj, the RPM is very hard to tell at altitude because when the humidity goes up it reallyyyyyy makes the engine lose a lot of HP. You can usually use a 3% drop in HP for every 1,000' of elevation, but that doesn't correlate very well to RPM. A 115 HP engine at 4,000' is only delivering about 102 HP.


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