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How Does Pitch Affect Fixed-Pitch Propeller RPM?

Asked by: 5500 views , ,
Aerodynamics, Aircraft Systems

Does a fixed-pitch prop's RPM change with pitch and given throttle setting? Does it spin faster because of the windmill effect or spin slower due to the load that is being placed on it?

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2 Answers



  1. Mark Kolber on Dec 16, 2014

    I’m going to take a stab at answering what I think this is asking.

    A propeller is an airfoil. It is really just another lifting surface like the wings. A fixed pitch prop is fixed with respect to the aircraft just as the wings are (angle of incidence). And just like the other airfoils on the airplane, its pitch with respect to the relative wind – angle of attack – can changed based on the airplane’s attitude. With a resulting change in RPM.

    The most common example of this is one you can see every time you fly. Set the power for 2400 RPM in cruise. If you don’t touch the throttle, RPM will decrease when you climb and increase when you descend due to your changes in pitch attitude.

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  2. Drew on Dec 17, 2014

    Thanks for the response. That does make sense. I’ve reworded the question to say what I mean. So a greater AoA produces more lift, which in turn slows the RPM. I assume it’s the increased induced drag of the prop that counteracts the RPM, since the propeller is just like a wing.

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