PPRuNe Forums - How to maintain the same rpm at different altitude?

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tyyshxxx

27th Aug 2019 15:57

How to maintain the same rpm at different altitude?

I am studying the FAA handbook and that under the topic fixed-pitch propeller, it says "

As altitude increases, the throttle must be opened further to indicate the same rpm as at a lower altitude"

Why is that? Isn't it when density decreases, lower power is needed to maintain the same rpm?

AerocatS2A

27th Aug 2019 19:57

The lower density also results in less air available for combustion in the engine. This effect is larger than the reduced drag on the prop.

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