Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Wing Span Efficiency Factor

  1. Nov 28, 2013 #1
    Hello Everybody,

    Span efficiency factor appears in the lifting-line theory of Prandtl describing Lift and vortex drag of a finite wing. According to this theory, the most efficient wing is an elliptical one and, roughly speaking, the span efficiency factor defines an efficiency of a given wing planform relatively to elliptic wing.

    In the framework of the lifting line theory the span efficiency cannot exceed 1.

    My question is: can this efficiency factor be more than 1, when going beyound lifting-line approximation ? (sorry for abusing notion of efficiency which supposed to be less <= 1).

    In other words: does it exist such a wing whose induced drag is less than that of estimate for elliptic wing in the lifting-line theory (provided aspect ratios and lift coefficients are the same and viscous effects, such as skin friction and boundary layer, are neglected).

    Last edited: Nov 28, 2013
  2. jcsd
  3. Dec 9, 2013 #2
    Short answer is yes, you can have a >1 efficiency factor. But you have to cheat. It's accomplished by using tandem wings or boxed wings. Winglets also allow for a >1 factor.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Similar Threads - Wing Span Efficiency Date
How to get greater lift from an aircraft wing Feb 15, 2018
Aerospace Effective Reynolds Number for a swept wing Jan 21, 2018
Aerospace Calculating Aerodynamic properties of a wing on ANSYS (Fluent) Dec 6, 2017
Wing semi span Feb 26, 2014
Aerospace Swept wings, Mcr and Span-wise flow Sep 11, 2011