Validation in Flight
As Whitcomb was discovering the area rule, Convair in San Diego, CA, was finalizing its design of a new supersonic all-weather fighter-interceptor, began in 1951, for a substantial Air Force contract. The YF-102 Delta Dagger combined Mach’s ideal high-speed bullet-shaped fuselage and delta wings pioneered on the Air Force’s Convair XF-92A research airplane with the new Pratt & Whitney J57 turbojet, the world’s most powerful at 10,000 pounds thrust. Armed entirely with air-to-air and forward-firing missiles, the YF-102 was to be the prototype for America’s first piloted air defense weapon’s system. Convair heard of the NACA’s transonic research at Langley and feared that its investment in the YF-102 and the payoff with the Air Force would come to naught if the new airplane could not fly supersonic. Convair’s reputation and a considerable Department of Defense contract were at stake.
A delegation of Convair engineers visited Langley in mid-August 1952, where the engineers witnessed a disappointing test of an YF-102 model in the 8-foot HST. The data indicated, according to the NACA at least, that the YF-102 was unable to reach Mach 1 in level flight. The transonic drag exhibited near Mach 1 simply counteracted the ability of the J57 to push the YF-102 through the sound barrier. They asked Whitcomb what could be done, and he unveiled his new rule of thumb for the design of supersonic aircraft. The data, Whitcomb’s solution, and what was perceived as the continued skepticism on the part of his boss, John Stack, left the Convair engineers unconvinced as they went back to San Diego with their model. They did not yet see the area rule as the solution to their perceived problem.
Nevertheless, Whitcomb worked with Convair’s aerodynamicists to incorporate the area rule into the YF-102. New wind tunnel evaluations in May 1953 revealed a nominal decrease in transonic drag. He traveled to San Diego in August to assist Convair in reshaping the YF-102 fuselage. The NACA notified Convair that the modified design, soon be designated the YF-102A, was capable of supersonic flight in October.
Despite the fruitful collaboration with Whitcomb, Convair was hedging its bets when it continued the production of the prototype YF-102 in the hope that it was a supersonic airplane. The new delta wing fighter with a straight fuselage was unable to reach its designed supersonic speeds during its full-scale flight evaluation and tests by the Air Force in January 1954. The disappointing performance of the YF-102 to reach only Mach 0.98 in level flight confirmed the NACAs wind tunnel findings and validated Whitcomb’s research that led to his area rule. The Air Force realistically shifted the focus toward production of the YF-102A after NACA Director Hugh Dryden guaranteed that Chief of Staff of the Air Force Gen. Nathan F. Twining developed a solution to the problem and that the information had been made available to Convair and the rest of the aviation industry. The Air Force ordered Convair to stop production of the YF-102 and retool to manufacture the improved area rule design.
It took Convair only 7 months to prepare the prototype YF-102A, thanks to the collaboration with Whitcomb. Overall, the new fighter-interceptor was much more refined than its predecessor was, with sharper features at the redesigned nose and canopy. An even more powerful version of the J57 turbojet engine produced 17,000 pounds thrust with afterburner. The primary difference was the contoured fuselage that resembled a wasp’s waist and obvious fairings that expanded the circumference of the tail. With an area rule fuselage, the newly re-designed YF-102A easily went supersonic. Convair test pilot Pete Everest undertook the second flight test on December 21, 1954, during which the YF-102A climbed away from Lindbergh Field, San Diego, and "slipped easily past the sound barrier and kept right on going.” More importantly, the YF-102A’s top speed was 25 percent faster, at Mach 1.2.
The Air Force resumed the contract with Convair, and the manufacturer delivered 975 production F-102A air defense interceptors, with the first entering active service in mid-1956. The fighter-interceptors equipped Air Defense Command and United States Air Force in Europe squadrons during the critical period of the late 1950s and 1960s. The increase in performance was dramatic. The F-102A could cruise at 1,000 mph and at a ceiling of over 50,000 feet. It replaced three subsonic interceptor aircraft in the Air Force inventory—the North American F-86D Sabre, F-89 Scorpion, and F-94 Starfire—which were 600-650 mph aircraft with a 45,000-foot ceiling range. Besides speed and altitude, the F-102A was better equipped to face the Soviet Myasishchev Bison, Tupolev Bear, and Ilyushin Badger nuclear-armed bombers with a full complement of Hughes Falcon guided missiles and Mighty Mouse rockets. Convair incorporated the F-102A’s armament in a drag – reducing internal weapons bay.
When the F-102A entered operational service, the media made much of the fact that the F-102 "almost ended up in the discard heap” because of its "difficulties wriggling its way through the sound barrier.” With an area rule fuselage, the F-102A "swept past the sonic problem.” The downside to the F-102A’s supersonic capability was the noise from its J57 turbojet. The Air Force regularly courted civic leaders from areas near Air Force bases through familiarization flights so that they would understand the mission and role of the F-102A.
The Air Force’s F-102 got a whole new look after implementing Richard Whitcomb’s area rule. At left is the YF-102 without the area rule, and at right is the new YF-102A version. NASA.
Convair produced the follow-on version, the F-106 Delta Dart, from 1956 to 1960. The Dart was capable of twice the speed of the Dagger with its Pratt & Whitney J75 engine. The F-106 was the primary air defense interceptor defending the continental United States up to the early 1980s. Convair built upon its success with the F-102A and the F-106, two cornerstone aircraft in the Air Force’s Century series of aircraft, and introduced more area rule aircraft: the XF2Y-1 Sea Dart and the B-58 Hustler.
The YF-102/YF-102A exercise was valuable in demonstrating the importance of the area rule and of the NACA to the aviation industry and the military, especially when a major contract was at stake. Whitcomb’s revolutionary and intuitive idea enabled a new generation of supersonic military aircraft, and it spread throughout the industry. Like Convair, Chance Vought redesigned its F8U Crusader carrier-based interceptor with an area rule fuselage. The first production aircraft appeared in September 1956, and deliveries began in March 1957. Four months later, in July 1957, Marine Maj. John H. Glenn, Jr., as part of Project Bullet,
made a recordbreaking supersonic transcontinental flight from Los Angeles to New York in 3 hours 23 minutes. Crusaders served in Navy and Marine fighter and reconnaissance squadrons throughout the 1960s and 1970s, with the last airframes leaving operational service in 1987.
Grumman was the first to design and manufacture from the ground up an area rule airplane. Under contract to produce a carrier-based supersonic fighter, the F9F-9 Tiger, for the Navy, Grumman sent a team of engineers to Langley, just 2 weeks after receiving Whitcomb’s pivotal September 1952 report, to learn more about transonic drag. Whitcomb traveled to Bethpage, NY, in February 1953 to evaluate the design before wind tunnel and rocket-model tests were to be conducted by the NACA. The tests revealed that the new fighter was capable of supersonic speeds in level flight with no appreciable transonic drag. Grumman constructed the prototype, and in August 1954, with company test pilot C. H. "Corky” Meyer at the controls, the F9F-9 achieved Mach 1 in level flight without the assistance of an afterburner, which was a good 4 months before the supersonic flight of the F-102A. The Tiger, later designated the F11F – 1, served with the fleet as a frontline carrier fighter from 1957 to 1961 and with the Navy’s demonstration team, the Blue Angels.
Another aircraft designed from the ground up with an area rule fuselage represented the next step in military aircraft performance in the late 1950s. The legendary Lockheed "Skunk Works” introduced the F-104 Starfighter, "the missile with a man in it,” in 1954. Characterized by its short, stubby wings and needle nose, the production prototype F-104, powered by a General Electric J79 turbojet, was the first jet to exceed Mach 2 (1,320 mph) in flight, on April 24, 1956. Starfighters joined operational Air Force units in 1958. An international manufacturing scheme and sales to 14 countries in Europe, Asia, and the Middle East ensured that the Starfighter was in frontline use through the rest of the 20th century.
The area rule profile of the Grumman Tiger. National Air and Space Museum.
The area rule opened the way for the further refinement of supersonic aircraft, which allowed for concentration on other areas within the synergistic system of the airplane. Whitcomb and his colleagues continued to issue reports refining the concept and giving designers more options to design aircraft with higher performance. Working by himself and with researcher Thomas L. Fischetti, Whitcomb worked to refine high-speed aircraft, especially the Chance Vought F8U-1 Crusader, which evolved into one of the finest fighters of the postwar era.
Spurred on by the success of the F-104, NACA researchers at the Lewis Flight Propulsion Laboratory in Cleveland, OH, estimated that innovations in jet engine design would increase aircraft speeds upward
of 2,600 mph, or Mach 4, based on advanced metallurgy and the sophisticated aerodynamic design of engine inlets, including variable-geometry inlets and exhaust nozzles. One thing was for certain: supersonic aircraft of the 1950s and 1960s would have an area rule fuselage.
The area rule gave the American defense establishment breathing room in the tense 1950s, when the Cold War and the constant need to possess the technological edge, real or perceived, was crucial to the survival of the free world. The design concept was a state secret at a time when no jets were known to be capable of reaching supersonic speeds, due to transonic drag. The aviation press had known about it since January 1954 and kept the secret for national security purposes. The NACA intended to make a public announcement when the first aircraft incorporating the design element entered production. Aero Digest unofficially broke the story a week early in its September 1955 issue, when it proclaimed, "The SOUND BARRIER has been broken for good,” and declared the area rule the "first major aerodynamic breakthrough in the past decade.” In describing the area rule and the Grumman XF9F-9 Tiger, Aero Digest stressed the bottom line for the innovation: the area rule provided the same performance with less power.
The official announcement followed. Secretary of the Air Force Donald A. Quarles remarked on the CBS Sunday morning television news program Face the Nation on September 11, 1955, that the area rule was "the kind of breakthrough that makes fundamental research so very important.” Aviation Week declared it "one of the most significant military scientific breakthroughs since the atomic bomb.” These statements highlighted the crucial importance of the NACA to American aeronautics.
The news of the area rule spread out to the American public. The media likened the shape of an area rule fuselage to a "Coke bottle,” a "wasp waist,” an "hourglass,” or the figure of actress Marilyn Monroe. While the Coke bottle description of the area rule is commonplace today, the NACA contended that Dietrich Kuchemann’s Coke bottle and Whitcomb’s area rule were not the same and lamented the use of the term. Kuchemann’s 1944 design concept pertained only to swept wings and tailored the specific flow of streamlines. Whitcomb’s rule applied to any shape and contoured a fuselage to maintain an area equivalent to the entire stream tube. Whitcomb actually preferred "indented.” One learned writer explained to readers of the Christian Science Monitor that an aircraft with an area rule slipped through the transonic barrier due to the "Huckleberry Finn technique,” which the character used to suck in his stomach to squeeze through a hole in Aunt Polly’s fence.
Whitcomb quickly received just recognition from the aeronautical community for his 3-year development of the area rule. The National Aeronautics Association awarded him the Collier Trophy for 1954 for his creation of "a powerful, simple, and useful method” of reducing transonic drag and the power needed to overcome it. Moreover, the award citation designated the area rule as "a contribution to basic knowledge” that increased aircraft speed and range while reducing drag and using the same power. As Vice President Richard M. Nixon presented him the award at the ceremony, Whitcomb joined the other key figures in aviation history, including Orville Wright, Glenn Curtiss, and his boss, John Stack, in the pantheon of individuals crucial to the growth of American aeronautics.
Besides the Collier, Whitcomb received the Exceptional Service Medal of the U. S. Air Force in 1955 and the inaugural NACA Distinguished Service Medal in 1956. At the age of 35, he accepted an honorary doctor of engineering degree from his alma mater, Worcester Polytechnic
Institute, in 1956. Whitcomb also rose within the ranks at Langley, where he became head of Transonic Aerodynamics Branch in 1958.
Whitcomb’s achievement was part of a highly innovative period for Langley and the rest of the NACA, all of which contributed to the success of the second aeronautical revolution. Besides John Stack’s involvement in the X-1 program, the NACA worked with the Air Force, Navy, and the aerospace industry on the resultant high-speed X-aircraft programs. Robert
T. Jones developed his swept wing theory. Other NACA researchers generated design data on different aircraft configurations, such as variable – sweep wings, for high-speed aircraft. Whitcomb was directly involved in two of these major innovations: the slotted tunnel and the area rule.