According to the common explanation which has two adjacent molecules separated at the leading edge mysteriously meeting at the trailing edge, the average air velocities on the top and bottom [of a wing] are in the ratio of 1.0074.

A typical speed for a model plane of 1m span and 0.16m chord with a mass of 0.7 kg (a weight of 6.9 N) is 10 ms-1 which makes 10.074 ms-1. Given these numbers, we find a pressure difference from the equation of about 0.9 kgm-1 - 2. The area of the wing 2s is 0.16 m giving a total force of 0.14 N. This is not nearly enough-—it misses lifting the weight of 6.9 N by a factor of about 50. We would need an air velocity difference of about 3 ms-1 to lift the plane.

The calculation is, of course, an approximation since Bernoulli’s equation assumes non viscous, incompressible flow and air is both viscous and compressible. But the viscosity is small and at the speeds we are speaking of air does not compress significantly. 

Accounting for these details changes the outcome at most a percent or so. None of these details affect the conclusion that the common explanation of how a wing generates lift—with its naïve application of the Bernoulli equation—fails quantitatively.

This quote is from the article, “Model Airplanes, The Bernoulli Equation, And The Coanda Effect” by Jef Raskin.

Jef Raskin was a professor at the University of California at San Diego and originated the Macintosh computer at Apple Computer Inc. He was a widely-published writer, an avid model airplane builder, and an active musician and composer. (See the appendix for a brief explanation of the Coanda Effect)