The lift of a wing of finite span at a certain angle of attack is less than the lift of a two dimensional airfoil (which corresponds to a wing of infinite span). In general, the lift loss due to the wing tips is more pronounced, as the wing span is reduced.
This effect also means that the angle of attack required to reach the same lift must be higher as the wing span is getting smaller. The relation mainly depends on the aspect ratio of the wing and can be approximated as follows.
Procedure (abbreviations and symbols are listed at the end of this page):
versus
angle of attack a. Convert from [1/°] to
[1/radian] by multiplying with 180° and dividing by p.
The slope can be calculated by taking the lift coefficients at two angles of
attack and subtracting them to give the DCl
the same must be done with the angles to yield Da.
(In general this value will be in the order of 5-6)
| Case AR <= 4 |  |
| Case AR > 4 |  |
Finally:
either calculate the lift coefficient CL for a given angle of attack for the finite wing:
| Symbol | Description |
|---|---|
| b | wing span |
| e | span efficiency factor, typically between 0.85 and 0.95 |
| S | wing area |
| a0 | lift slope dCL/dalfa of the infinite wing (2D airfoil) |
| a | lift slope dCL/dalfa of the finite wing (3D wing) |
| a0 | 2D zero lift angle of the infinite wing (2D airfoil) |
| a2D | 2D angle of attack of the infinite wing (2D airfoil) |
| a3D | 3D angle of attack of the finite wing (3D wing) |
|
lift coefficient of the infinite wing (2D wing) |
| CL | lift coefficient of the finite wing (3D wing) |
Last modification of this page: 21.05.18
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