Question

For very high aspect ratio wings, the lift curve slope resembles that of the airfoil.

(a) False

(b) True

I got this question during an interview.

I would like to ask this question from Prandtl’s Classical Lifting-Line Theory in chapter Flow over Airfoils over Finite Wing of Aerodynamics

Answer 1

Right option is (b) True

The explanation is: For any general wing planform lift slope is given by a=\(\frac {a_0}{1+\frac {a_0}{\pi AR}(1+\tau)}\) where τ is a function of the Fourier coefficients used to describe the planform area. As aspect ratio becomes very large (i.e. AR tends to ∞), we find a becomes a0 i.e. for very high aspect ratio wings, lift slope for wing and airfoil is the same. Prandtl verified this through experiments also.