Question

Which of the following is the correct formula for specific endurance?

(a) SE=\(\frac{V}{C}\frac{L}{D}\frac{1}{W}\)

(b) SE=\(\frac{V}{PC}\)

(c) SE=\(\frac{\eta}{C}\frac{L}{D}\frac{1}{W}\)

(d) SE=\(\frac{\eta}{CV}\frac{L}{D}\frac{1}{W}\)

This question was posed to me during an internship interview.

This interesting question is from Range and Endurance for Aircraft with Power Producing Engines in portion Cruising Performance of Aircraft Performance

Answer 1

Right option is (d) SE=\(\frac{\eta}{CV}\frac{L}{D}\frac{1}{W}\)

To explain: The correct formula for specific endurance is given by SE=\(\frac{\eta}{CV}\frac{L}{D}\frac{1}{W}\) where η is propeller efficiency, C is specific fuel consumption, L is lift, D is drag, V is velocity, W is weight. SE can also be written as SE=\(\frac{1}{CP}\) where C is specific fuel consumption and P is power.