Question

An aircraft needs to accelerate from 0.8M to 2.0M. What should be the mission segment weight fraction if fixed engine sizing is used?

(a) 0.956

(b) 0.9365

(c) 0.937

(d) 0.98052

This question was addressed to me by my college professor while I was bunking the class.

This intriguing question comes from Fixed-Engine Sizing in section Initial Sizing of Aircraft Design

Answer 1

Correct choice is (a) 0.956

To explain: For an aircraft that accelerates from 0.1M to 0.8M, the required fuel fraction is 0.9805.

Similarly, for 0.1M to 2.0M we required a fuel fraction of 0.937 typically.

Now to find fuel fraction for aircraft from 0.8M to 2.0M is given by,

Fuel fraction = (required fuel fraction for 0.1M to 2.0M)/(required fuel fraction for 0.1M to 0.8M)

= 0.937 / 0.9805 = 0.956.