Question

What is the value of specific endurance where the lift to drag ratio is 10, weight is 50000N, efficiency is 85% , velocity is 250m/s and specific fuel consumption is 7.43 kg/kW-hr?

(a) 30hr

(b) 57.6hr

(c) 10hr

(d) 50hr

The question was posed to me in unit test.

This intriguing question originated from Range and Endurance for Aircraft with Power Producing Engines topic in chapter Cruising Performance of Aircraft Performance

Answer 1

The correct choice is (b) 57.6hr

To explain I would say: The answer is . Given \(\frac{L}{D}\)=10, W=50,000kg, η=85%, C=4.25×10^-5kg/kW-hr, V=69.44km/hr. From the equation SE=\(\frac{\eta}{CV}\frac{L}{D}\frac{1}{W}\). On substituting the values we get SE= \(\frac{0.85}{69.44 \times 4.25 \times 10^{-8}}\)*10*\(\frac{1}{50000}\).

On solving above equation we get SE=57.6hr.