A frequently quoted rule of thumb in aircraft design is that

Last updated: 7/10/2022

A frequently quoted rule of thumb in aircraft design is that wings should produce about 1000 N of lift per square meter of wing. (The fact that a wing has a top and bottom surface does not double its area.) (a) At takeoff the aircraft travels at 58.0 m/s, so that the air speed relative to the bottom of the wing is 58.0 m/s. Given the sea level density of air to be 1.29 kg/m, how fast (in m/s) must it move over the upper surface to create the ideal lift? (b) How fast (in m/s) must air move over the upper surface at a cruising speed of 240 m/s and at an altitude where air density is one-fourth that at sea level? (Note that this is not all of the aircraft's lift--some comes from the body of the plane, some from engine thrust, and so on. Furthermore, Bernout's principle gives an approximate answer because flow over the wing creates turbulence.)