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Old 09-22-2008, 08:09 PM
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creyes123's Avatar
Join Date: Apr 2008
Location: Albuquerque, NM
Posts: 32

Adding to the brew...

I went back and changed the new chart to display propeller blade angle of attack and power required by airspeed. Attached is a screen shot of a generic 12x12 gas propeller at 15k RPM.

The initial dip in the power required occurs at about 15 degrees AOA, which is the stalling angle of the propeller blades. According to the aerodynamics books, this is as expected.

Maximum power required occurs at about 5 degrees AOA. This is close to the best L/D of the propeller's airfoil, which I found counterintuitive. I looked but couldn't find an easy explanation for this (though it matches what the books say). The interactions that these variables have with the propeller blade rotational airspeed and Reynolds number are definitely not obvious.

Carlos Reyes
Brainy calculator, so you don't have to be.
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