![]() ![]() And with less drag, the aircraft is using less fuel than it would otherwise consume. Now the aircraft can cruise at a higher subsonic speed and easily fly up into the supercritical range. Lift that is lost with less curvature on the upper surface of the wing is regained by adding more curvature to the upper trailing edge. This delays the onset of the shock wave and also reduces aerodynamic drag associated with boundary layer separation. As air moves across the top of a SCW it does not speed up nearly as much as over a curved upper surface. Supercritical wings have a flat-on-top "upside down" look. In rare cases, aircraft have also become uncontrollable due to boundary layer separation. This increases fuel consumption and it can also lead to a decrease in speed and cause vibrations. ![]() Separated boundary layers are like wakes behind a boat - the air is unsteady and churning, and drag increases. The shockwave causes the smooth flow of air hugging the wing's upper surface (the boundary layer) to separate from the wing and create turbulence. ![]() The aircraft, at this point, is flying at what is called the critical speed. This creates a shock wave on the wing's upper surface even though the aircraft, as a whole, has not exceeded Mach 1. When an aircraft with a conventional wing nears a speed of sound (Mach 1), air flowing across the top of the wing moves faster and becomes supersonic. The F-111 program, while it did not lead to a SCW retrofit for the entire F-111 fleet, did produce data that is available to the aerospace industry for development of future aircraft. Results were extremely successful and showed the test wing generated up to 30% more lift than the conventional F-111 wing and performed as expected at all wing-sweep angles. An F-111, with a variable-geometry wing, was the test aircraft and the basic supercritical research took place between 19. Air Force teamed with NASA for a joint program to test a SCW designed for highly maneuverable military aircraft. NASA's test program validating the SCW concept was conducted at the Dryden Flight Research Center from March 1971 to May 1973 and showed that the SCW installed on an F-8 Crusader test aircraft increased transonic efficiency by as much as 15%.īefore the program ended, the U.S. The SCW is flatter on the top, rounded on the bottom, and the upper trailing edge is accented with a downward curve to restore lift lost by flattening the upper surface.Īt speeds in the transonic range - just below and just above the speed of sound - the SCW delays the formation of the supersonic shock wave on the upper wing surface and reduces its strength, allowing the aircraft to fly faster with less effort. (NASA Photo E73-3468)Ĭalled the supercritical airfoil, the design has led to development of the supercritical wings (SCW) now used worldwide on business jets, airliners and transports, and numerous military aircraft.Ĭonventional wings are rounded on top and flat on the bottom. ![]() Supercritical wings add a graceful appearance to the modified NASA F-8 test aircraft. An airfoil considered unconventional when tested in the early 1970s by NASA at the Dryden Flight Research Center is now universally recognized by the aviation industry as a wing design that increases flying efficiency and helps lower fuel costs. ![]()
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