Question

A subsonic flight has actual inlet pressure recovery of 0.975. Estimate the thrust loss by this subsonic engine.

(a) 3.37%

(b) 56%

(c) 2.5%

(d) 11.22%

This question was addressed to me in final exam.

This intriguing question comes from Propulsion topic in chapter Propulsion of Aircraft Design

Answer 1

Right choice is (a) 3.37%

The best explanation: Given, subsonic Aircraft, actual inlet pressure recovery = 0.975.

Thrust loss can be approximated as follows,

% Thrust loss = C*(reference pressure recovery – actual inlet pressure recovery)*100

Since, C is not given we will consider it as 1.35. 1.35 is a typical value of C for subsonic aircraft.

Hence,

% Thrust loss = 1.35*(1-.975)*100 = 3.37%.