Question

What is the inflow ratio for hovering?

(a) 1-1.5

(b) 0.05-0.07

(c) 0.6-1

(d) 0.01-0.05

I got this question in class test.

This intriguing question originated from Blade Element Theory topic in division Helicopter Dynamics of Aerodynamics

Answer 1

The correct answer is (b) 0.05-0.07

For explanation: Inflow ratio is a nondimensional quantity that is used to compare the results from different rotor blades. The formula for inflow ratio is given by:

λ=\(\frac {V+v}{ΩR}\)

Where, V is the climb velocity which is zero for hovering

v is the induced velocity

Ω is the rate of rotation of the blade

R is the radius

The value of inflow ratio ranges between 0.05 and 0.07 for hovering.