Question

A general aviation single engine aircraft has gross weight of 2800lb. The aircraft has maximum speed of 130mph. Determine the approximated value of empty weight fraction if, aspect ratio AR is 9, wing loading is 15 and power loading is 12.

(a) 0.5476

(b) 0.6457

(c) 0.8962

(d) 0.9028

I had been asked this question in final exam.

The origin of the question is Rubber-Engine Sizing in section Initial Sizing of Aircraft Design

Answer 1

Correct option is (a) 0.5476

Explanation: Given, a general aviation aircraft with single engine.

Maximum velocity Vmax =130mph

Gross weight W0 = 2800lb, wing loading = W.L. = 15, Aspect ratio AR = 9, Power loading P.L. = 12.

For, given parameters empty weight fraction is given by,

We/W0 = a + b*(W0^c)*(AR ^d)*(P.L.^-e)*(W.L.^f)*(Vmax^g)

Now, for general aviation with single engine, a=-0.25, b = 1.14, c = -0.2, d = 0.08, e = 0.05, f = -0.05, g = 0.27.

Hence, empty weight fraction is given by,

We/W0 = -0.025 + 1.14*(W0^-0.2)*(AR ^0.08)*(P.L.^-0.05)*(W.L.^-0.05)*(Vmax^0.27)

We/W0 = -0.025 + 1.14*(2800^-0.2)*(9 0.08)*(12^-0.05)*(15^-0.05)*(130^0.27)

We/W0 = -0.025 +.07976 = 0.5476.