Tunnel Visions: Dick Whitcomb’s Creative Forays

The slotted-throat transonic tunnels pioneered by John Stack and his associates at Langley proved valuable, especially in the hands of one of the Center’s more creative minds, Richard. T. Whitcomb. In the 8-Foot TT, he investigated the transonic regime. Gaining a better understanding of aircraft speeds between Mach 0.75 and 1.25 was one of the major aero­dynamic challenges of the 1950s and a matter of national security during the Cold War. The Air Force’s Convair YF-102 Delta Dagger interceptor was unable to reach supersonic speeds during its first flights in 1953. Tests in the 8-Foot TT revealed that the increase in drag as an airplane approached supersonic speeds was not the result of shock waves form­ing at the nose but of those forming just behind the wings. Whitcomb created a rule of thumb that decreased transonic drag by narrowing, or pinching, the fuselage where it met the wings.[565] The improved YF-102A, with its new "area rule” fuselage, achieved supersonic flight in December 1954. The area rule fuselage increased the YF-102A’s top speed by 25 per­cent. Embraced by the aviation industry, Whitcomb’s revolutionary idea enabled a generation of military aircraft to achieve supersonic speeds.[566]

As he worked to validate the area rule concept, Whitcomb moved next door to the 8-Foot Transonic Pressure Tunnel (TPT) after it opened in 1953. His colleagues John Stack, Eugene C. Draley, Ray H. Wright, and Axel T. Mattson designed the facility from the outset as a slotted – wall transonic tunnel with a maximum speed of Mach 1.2.[567] In what quickly became known as "Dick Whitcomb’s tunnel,” he validated and made two additional aerodynamic contributions in the decades that followed—the supercritical wing and winglets.

Beginning in 1964, Whitcomb wanted to develop an airfoil for com­mercial aircraft that delayed the onset of high transonic drag near Mach 1 by reducing air friction and turbulence across an aircraft’s major aero­dynamic surface, the wing. Whitcomb went intuitively against conven­tional airfoil design by envisioning a smoother flow of air by turning a conventional airfoil upside down. Whitcomb’s airfoil was flat on top with a downward curved rear section. The blunt leading edge facilitated better takeoff, landing, and maneuvering performance as the airfoil slowed airflow, which lessened drag and buffeting and improved stabil­ity. Spending days at a time in the 8-Foot TPT, he validated his concept with a model he made with his own hands. He called his innovation a "supercritical wing,” combining "super” (meaning "beyond”) with "crit­ical” Mach number, which is the speed supersonic flow revealed itself above the wing.[568] After a successful flight program was conducted at NASA Dryden from 1971 to 1973, the aviation industry incorporated the supercritical wing into a new generation of aircraft, including sub­sonic transports, business jets, Short Take-Off and Landing (STOL) air­craft, and unmanned aerial vehicles (UAVs).[569]

Whitcomb’s continual quest to improve subsonic aircraft led him to investigate the wingtip vortex, the turbulent air found at the end of an airplane wing that created induced drag, as part of the Aircraft Energy Efficiency (ACEE) program. His solution was the winglet, a vertical wing­like surface that extended above and sometimes below the tip of each

wing. Whitcomb and his research team in the 8-Foot TPT investigated the drag-reducing properties of winglets for a first-generation, narrow – body subsonic jet transport from 1974 to 1976.[570] Whitcomb found that winglets reduced drag by approximately 20 percent and doubled the improvement in the lift-to-drag (L/D) ratio, to 9 percent, which boosted performance by enabling higher cruise speeds. The first jet-powered airplane to enter production with winglets was the Learjet Model 28 in 1977. The first large U. S. commercial transport to incorporate winglets, the Boeing 747-400, followed in 1985.[571]