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I've been trying to get my head around wing design and have been following a few YouTube videos. When people talk about aspect ratio (AR) on a wing and give a value (Piper PA28 having an AR of 5.7) what is the 5.7? Is it wingspan length? Square metre of coverage? Or something else? I'm confused.


marked as duplicate by fooot, kepler22b, SMS von der Tann, Jay Carr, Ralph J Apr 26 '16 at 20:27

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The Aspect Ratio ($AR$) is defined as the ratio (hence the name) between the wingspan squared $b^2$ and the area of the wing $S$.

Since both $b^2$ and $S$ are measured with a length squared (e.g., $m^2$), $AR$ is an dimensionless quantity.

To answer the follow-on question of TomMcW in the comments, $b$ is the distance between the wingtips, no matter the shape of the wing.

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    $\begingroup$ How is wingspan figured on a swept wing? Is it perpendicular distance between wingtip and fuselage or length of leading edge? $\endgroup$ – TomMcW Apr 26 '16 at 17:15

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