Checked content

File:Equal transit-time NASA wrong1.gif

Equal_transit-time_NASA_wrong1.gif(586 × 264 pixels, file size: 4 KB, MIME type: image/gif)



There are many theories of how lift is generated. Unfortunately, many of the theories found in encyclopedias, on web sites, and even in some textbooks are incorrect, causing unnecessary confusion for students.

The theory described on this slide is one of the most widely circulated, incorrect explanations. The theory can be labeled the "Longer Path" theory, or the " Equal Transit Time" theory. The theory states that airfoils are shaped with the upper surface longer than the bottom. The air molecules (the little colored balls on the figure) have farther to travel over the top of the airfoil than along the bottom. In order to meet up at the trailing edge, the molecules going over the top of the wing must travel faster than the molecules moving under the wing. Because the upper flow is faster, then, from Bernoulli's equation, the pressure is lower. The difference in pressure across the airfoil produces the lift.


Image was cropped from original slide.

Date 1 June 2009
Source en:File:Equal_transit-time_NASA_wrong1.gif
Author NASA
( Reusing this file)



Public domain This file is in the public domain because it was solely created by NASA. NASA copyright policy states that "NASA material is not protected by copyright unless noted". (See Template:PD-USGov, NASA copyright policy page or JPL Image Use Policy.)
NASA logo.svg
  • Use of NASA logos, insignia and emblems are restricted per US law 14 CFR 1221.
  • The NASA website hosts a large number of images from the Soviet/ Russian space agency, and other non-American space agencies. These are not necessarily in the public domain.
  • Materials based on Hubble Space Telescope data may be copyrighted if they are not explicitly produced by the STScI. See also {{ PD-Hubble}} and {{ Cc-Hubble}}.
  • The SOHO (ESA & NASA) joint project implies that all materials created by its probe are copyrighted and require permission for commercial non-educational use.
  • Images featured on the Astronomy Picture of the Day (APOD) web site may be copyrighted.
The following pages on Schools Wikipedia link to this image (list may be incomplete):

Did you know...?

Learning is fun and easy with Schools Wikipedia. By supporting vulnerable children right through to adulthood, SOS Childrens Villages makes a lasting difference to the lives of thousands of people. Education is a key part of our work, and our schools provide high-quality teaching to the children in our care. Will you help another child today?