Wetted aspect ratio (wing)

The wetted aspect ratio is a good indication of the aerodynamic efficiency of an aircraft. It is a better measure than the aspect ratio. It is defined as:

$\mathit{AR}_{\mathrm{wet}} = {b^2 \over S_w}$

where b is span and S_w is the wetted surface (the entire surface area of the airframe exposed to airflow) of the whole aircraft in contrast to the wing area used for the definition of the aspect ratio.

A good example of this is the Boeing B-47 and Avro Vulcan. Both aircraft have very similar performance although they are radically different. The B-47 has a high aspect ratio wing, while the Avro Vulcan is a low aspect ratio blended wing body. They have, however, a very similar wetted aspect ratio.