Expert: Paul Soderman - 9/23/2008

Question
Pumps transfer energy from a source(engine) to a fluid (air). Why is a propellar considered a rotating wing and not a pump with the pitch of the propellar defining the efficiency of the pump and the resulting speed/volume of the air flow across the wing defined by the pressure differential created across the propellar blade.

Answer
Rick
I think of a pump as a device that moves fluid from one place to another or generates pressure in a fluid. A propeller also moves fluid, but that is not its primary purpose.  A propeller is a propulsive device that generates thrust so it is somewhat of a stretch to think of a propeller as a pump. The blades are analogous to rotating wings, but we usually just call them blades.  

Propeller efficiency is a well defined term that relates propeller power generated to power input.  See:
http://www.jefflewis.net/aviation_theory-theo_prop_eff.html

The blade pitch or angle of attack is important but incidental to the power generated.

You are correct, propeller mass flow is created by the pressure differential across the blades, but I don't understand your question in detail.
Paul