Eli5: Why airplanes have shorter propellers, when long helicopter propellers could move more air?

Question

Isn’t forward motion created by moving more air?

In: Engineering

Answer 1

A fixed-wing aircraft has wings that provide lift, given sufficient airspeed. The propellers only need to contribute the airspeed. The helicopter’s rotors need to be large enough to lift the aircraft.

There are some hybrid, known as “tiltrotor,” aircraft, like the V-22 Osprey, that have very large propellers so that they can be aligned differently to serve in either role.