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The blue and light green shapes are roughly equal in area. The Whitcomb area rule, named after NACA engineer Richard Whitcomb and also called the transonic area rule, is a design procedure used to reduce an aircraft's drag at transonic speeds which occur between about Mach 0.75 and 1.2.
Anti-shock body is the name given by Richard T. Whitcomb to a pod positioned on the upper surface of a wing. [1] Its purpose is to reduce wave drag while travelling at transonic speeds (Mach 0.8–1.0), which includes the typical cruising range of conventional jet airliners.
Transonic airspeeds see a rapid increase in drag from about Mach 0.8, and it is the fuel costs of the drag that typically limits the airspeed. Attempts to reduce wave drag can be seen on all high-speed aircraft. Most notable is the use of swept wings, but another common form is a wasp-waist fuselage as a side effect of the Whitcomb area rule.
In the United States, the supercritical airfoil was an area of research during the 1960s; one of the leading American figures in the field was Richard Whitcomb. A specially modified North American T-2C Buckeye functioned as an early aerial testbed for the supercritical wing, performing numerous evaluation flights during this period in support ...
After World War II, NACA research began to focus on near-sonic and low-supersonic airflow.After considering the sudden drag increase which a wing-fuselage combination experiences at somewhere around 500 mph (800 km/h), Whitcomb concluded that "the disturbances and shock waves are simply a function of the longitudinal variation of the cross-sectional area" – that is, the effect of the wings ...
Jet aircraft are usually designed using the Whitcomb area rule, which says that the total area of cross-section of the aircraft at any point along the aircraft from the nose must be approximately the same as that of a Sears-Haack body. A shape with that property minimises the production of shockwaves which would waste energy.
Fuselage shaping was similarly changed with the introduction of the Whitcomb area rule. Whitcomb had been working on testing various airframe shapes for transonic drag when, after watching a presentation by Adolf Busemann in 1952, he realized that the Sears-Haack body had to apply to the entire aircraft, not just the fuselage. This meant that ...
Designers use the Supersonic area rule and the Whitcomb area rule to minimize sudden changes in size. The sound source is traveling at 1.4 times the speed of sound, c (Mach 1.4). Because the source is moving faster than the sound waves it creates, it actually leads the advancing wavefront.