- Supercritical airfoil
, it has since been mainly applied to increase the fuel efficiency of many high subsonic aircraft. Research in 1940 by DVL's K. A. Kawalki led to subsonic profiles very similar to the supercritical profiles, which was the basis for the objection in 1984 against the US-patent specification for the supercritical airfoil. [Hans-Ulrich Meier, Die Pfeilflügelentwicklung in Deutschland bis 1945, ISBN 3763761306 Einspruch (1984) gegen US-Patentschrift NASA über »superkritische Profile«, basierend auf den Berechnungsmethoden von K. H. Kawalki (1940) p.107 german] The supercritical airfoil shape is incorporated into the design of a supercritical wing.
Research aircraft of the 1950s and 60s found it difficult to break the sound barrier, or even reach Mach 0.9, with conventional airfoils.
Supersonicairflow over the upper surface of the traditional airfoil induced excessive wave dragand a form of stability loss called Mach tuck. Due to the airfoil shape used, supercritical wings experience these problems less severely and at much higher speeds, thus allowing the wing to maintain high performance at speeds closer to Mach 1. Techniques learned from studies of the original supercritical airfoil sections are used to design airfoils for high-speed subsonic and transonic aircraft from the Boeing 777to the McDonnell Douglas AV-8B Harrier II.
Supercritical airfoils have four main benefits: they have a higher . Compared to a typical airfoil section, the supercritical airfoil creates more of its lift at the aft end, due to its more even pressure distribution over the upper surface.
In addition to improved transonic performance, a supercritical wing's enlarged leading edge gives it excellent high-lift characteristics. As a result, aircraft utilizing a supercritical wing have superior takeoff and landing performance. This makes the supercritical wing a favorite for designers of cargo transport aircraft. A notable example of one such heavy-lift aircraft that uses a supercritical wing is the
C-17 Globemaster III.
Whitcomb area rule
* [http://www.aerospaceweb.org/question/airfoils/q0003.shtml Supercritical airfoil at Aerospaceweb]
* [http://www.century-of-flight.freeola.com/Aviation%20history/evolution%20of%20technology/Supercritical%20Airfoil.htm Supercritical airfoil at century-of-flight]
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