|The supercritical aerofoil was designed in the 1960's by NASA engineer Richard Whitcomb. Its unique cross-sectional shape delays the onset of wave drag in the transonic speed range and thus allows aircraft to fly faster and more efficiently. The shape of this wing design is characterised by a rounded leading edge and a flat upper surface which delays the development of a shock wave. The rear of the aerofoil features a reflex cambered under-section which helps the wing develop lift at lower airspeeds (Wikipedia, 2011).||
Early supersonic aircraft found it very difficult to break the sound-barrier because of the wave drag created by traditional aerofoils. In the early 1960, NASA engineer Richard Whitcomb proposed a new aerofoil shape that he believed would overcome these complications. Initial wind tunnel tests suggested the aerofoil would allow aircraft to fly 10% faster and would be better able to break through the sound barrier. Full scale testing was varied out of a modified Vought F-8U and these studies were confirmed.
Not only did the supercritical aerofoil allow aircraft to break the sound barrier but it also allowed them to cruise much closer to the speed out sound whilst delaying the onset of wave-drag. Passenger airliners at the time, such as the Boeing 707, were limited to cruise speeds of around 0.70-0.80 mach. By employing the supercritical aerofoil the aircraft could safely reach speed of 0.90-0.95 mach, alternatively, they could continue to cruise at their normal speeds but burn significantly less fuel (Day, 2004).
Today, supercritical aerofoils are employed on many aircraft. The Air Force cargo transport plane, the C17 employs a supercritical aerofoil giving it excellent performance for an aircraft of its size. Most notably, the Boeing 777 is also designed with a supercritical wing and as such is the most efficient commercial wing ever invented (Boeing Company, n.d.).
Want to know more?
- US Centennial of Flight Commission - Supercritical Aerofoil
- History and Explanation of Super Critical Aerofoils
- NASA Supercritical Aerofoils
- Detailed Scientific Explanation of Super Critical Aerofoils