Expert: Paul Soderman - 9/22/2008

Question
Dear Mr. Soderman

I am a high school senior doing a research paper about the physics of flight and I am having trouble finding out how propellers work. I understand that a propeller is pretty much a set of spinning wings. I don't understand what the propeller pitch is. Is it just the propeller's angle of attack or is it something else? Also, what purpose does the nose cone serve? lastly, what constitutes additional wings on a propeller?

Any assistance that you can provide will be greatly appreciated. Thank you for your time and help.

Answer
Seth
You are correct, propeller blades are spinning wings, and pitch is the propeller blade's angle of attack.  Because the speed of each propeller section varies with radial distance from the hub, the propeller is usually twisted to set the angles of attack relative to the local airflow such that none of the sections stall.  It is common to refer to the propeller pitch as the angle of the section at the 3/4 radius station relative to the plane of the propeller.  It is also common to define pitch as the distance the propeller travels in one revolution assuming no slip.  The two measures are equivalent.

The nose cone is simply an aerodynamic cover that hides the hub. As you can imagine, the blades must attach to the propeller shaft with big bolts and such.  That must be made aerodynamic to minimize drag and turbulence.

I don't understand your question about additional wings.

Good luck with your project.
Paul