Question

Which of the following represents the correct formula for propeller efficiency?

(a) η=\(\frac{T}{P}\)

(b) η=\(\frac{P}{TV}\)

(c) η=\(\frac{T}{PV}\)

(d) η=\(\frac{TV}{P}\)

The question was asked at a job interview.

The question is from Power Producing Power Plant in section Aircraft Force Systems and the Equations of Motion of Aircraft Performance

Answer 1

Right choice is (d) η=\(\frac{TV}{P}\)

Easiest explanation: The correct formula for propeller efficiency is η=\(\frac{TV}{P}\) where η is propeller efficiency T is thrust and V is true airspeed and P is shaft power. The propeller efficiency is the ratio of thrust-power output by the shaft power input of a powerplant engine.