Richard Whitcomb's Triple Play

The most gifted and influential aeronautical researcher of his time knew a thing, or two, or three. Richard Whitcomb’s Triple Play USAF photo

n 1953, the Air Force had a problem: Its new jet-powered

interceptor, Convair’s F-102, NACA photo was a dud. IUnlike earlier airplanes that relied on brute strength to push past the speed of sound, the dart-shaped F-102 had a “delta” wing and an afterburning engine that was supposed to allow it to slip across the sonic frontier. Dubbed the “1954 Interceptor” (a reference to its planned in-service date), the new F-102 was to scramble from US bases, climb to high altitude, and intercept incoming Soviet bombers, dashing if necessary to Mach 1.25 before blasting them from the sky. On paper, it seemed a winner. High over the Mojave, flight tests were starting to show otherwise. As the prototype YF-102 approached the speed of sound, it would begin to slow down, like a marathon runner hitting the 20 Mile wall. Even with its afterburner blasting away, the aircraft would top out at only Mach 0.98 before returning to Earth. It was 68 AIR FORCE Magazine / February 2010 Whitcomb, below left, with an early wind tunnel model featuring the “wasp-waist.” His flash of genius led to the Area Rule, which made it possible to increase the special insight into the physics of fluid speed of the experimental YF-102 (top left) 25 percent by the time it became the flow. He initially used that intuition, operational F-102A interceptor (below). not just quantitative analysis, when he derived his Area Rule theory. His intuition thus directly led to one of the most important design innovations in aviation history.” Born in Illinois in 1921, Whitcomb came from a family attuned to technology and invention. His father, a mechanical Richard Whitcomb’s Triple Play engineer, had been a balloon pilot, and his grandfather was an inventor who By Richard P. Hallion had known Thomas Edison. Convair photo

clear that something was very wrong at age 88, has been rightly acclaimed Like many boys of his generation, with Convair’s new delta. Could it be as the most gifted and influential Whitcomb was fascinated with flight salvaged? aeronautical researcher of his time. and earned an engineering scholarship The answer was yes. The F-102 to Massachusetts’ Worcester Poly- would require extensive redesign, de- Incredible Insight technic Institute. Most engineering laying its introduction into service by An aerodynamicist with the National students aspired to work in industry, two years, but it would become a Cold Advisory Committee for Aeronautics but Whitcomb was different: “I knew,” War mainstay, with approximately (NACA, the predecessor of NASA), he said later, “that I wanted to go into 1,000 serving from 1956 through 1976 Whitcomb was a standout even in an research.” in Air Force and Air National Guard agency known for the extraordinary As he approached graduation, he interceptor squadrons (and in the mili- quality of its scientific personnel. read a Fortune magazine article extol- taries of Greece and Turkey as well). “Dick Whitcomb wasn’t just an- ling NACA’s Langley Memorial Aero- That the F-102 didn’t remain an other brilliant aerodynamicist,” notes nautical Laboratory at Langley Field, embarrassing failure was thanks to the former Air Force Chief Scientist and Va. (now the NASA Langley Research genius of a young government engi- University of Maryland professor Center at Langley Air Force Base). neer, Richard T. Whitcomb. Whitcomb, Mark J. Lewis, who knew him. “He The article convinced him it “was the who died last October in Hampton, Va., had incredible intuition, giving him place to come for applied research.” AIR FORCE Magazine / February 2010 69 waves, enabling much more accurate measurements as airflows neared and NASA photo exceeded the speed of sound. Whitcomb made the slotted throat tunnel his personal laboratory. In the early years of the postwar era, NACA aerodynamicists focused on the be- havior of the swept wing. Whitcomb looked beyond its singular purity, studying instead the aerodynamic interaction of the wing and fuselage. He discovered their combined drag was greater than the sum of their individual drags measured separately. Using photographic imaging, Whit- comb noted strong shock waves ema- nating where the leading and trailing edges of wings joined the fuselage, producing a performance-robbing “bunching” of air. It was as if the wave patterns of two boats intersected, becoming just one large pattern. “The theoreticians,” he later told one interviewer, “were at a loss as to how to handle this problem.” All except one—Adolf Busemann, a sci- entist who had invented the high-speed swept wing in Germany before World War II, and who came to Langley with Project Paperclip afterward. At a staff seminar, Busemann joked that The winglet (seen here in testing on a KC-135) later became crucial to the C-17’s performance. Seemingly simple, the winglet adds lift far beyond its cost in weight, transonic flows were so constricted and has been adopted on many airliners. that aerodynamicists were like pipe fitters, finding how to fit flows around the vehicle. Accordingly, when a NACA recruiter With a surprising outspokenness for One day in 1951, while Whitcomb visited Worcester Poly, Whitcomb someone so young, he refused. contemplated his tunnel results and recalled, “I was just waiting for the “I said, ‘I don’t want to work in pondered Busemann’s analogy, he guy to hand me the papers.” instruments,’ ” he recalled. “ ‘I want had an insight like a flash of light: Whitcomb joined NACA in 1943, to work on aerodynamics.’ ” So they If a designer gave the bunching air a the year when America’s aeronautical assigned him to the Langley eight-foot place to go, the flow would smooth community began planning its as- high-speed tunnel, run by John Stack. out, and the drag would decrease. He sault upon the then-fearsome “sound NACA’s most forceful high-speed re- later recalled the moment, saying, “I barrier.” search enthusiast, Stack was energetic, sat there at my desk, feet propped up, The rocket and the jet now made insightful, charismatic, and destined and suddenly it dawned on me, the supersonic flight a possibility. Perhaps to twice share the Robert J. Collier basic idea of the Area Rule: Transonic an airplane could fly faster than sound, Trophy—the most prestigious of all drag is a function of the longitudinal if it could first survive the intermediate American aviation accolades. development of the cross-sectional transonic region with its much-feared areas of the entire plane.” sound barrier. A Flash of Light It was the latter insight—that drag The transonic region was between Chief among his many accomplish- was a function of the length of the Mach 0.75 and Mach 1.25. In that band, ments was conceptualizing and devel- entire airplane and not just the fuselage airplanes encountered compressible oping the slotted throat wind tunnel, the diameter at the wing-fuselage junc- flow, shock waves streaming from most significant tunnel advance over ture—which separated Whitcomb’s their wings and bodies, loss of lift and the previous 25 years. Conventional work from others who focused their rising drag, dangerous buffeting, and wind tunnels “choked” near the speed research more narrowly. sometimes loss of control and even of sound when shock waves streaming The ideal supersonic shape was long structural failure. from models reflected back and forth and slender, with its cross-sectional Whitcomb would prove his mastery across their test sections, producing area expanding gradually, reaching over this treacherous and daunting misleading or incomprehensible re- a maximum diameter and then con- arena but almost missed the chance. sults. The slotted throat tunnel removed tracting equally smoothly. Designers When he arrived at Langley, personnel this transonic “blind spot” via a ring would have to pinch the fuselage at the staffers initially assigned him to the of carefully placed longitudinal slots wing roots, and lengthen the fuselage instrumentation branch. that dissipated flow-disturbing shock before and behind the wing as well, 70 AIR FORCE Magazine / February 2010 Whitcomb with a wind tunnel model of a TF-8 configured with his supercriti- cal wing (below), and NASA’s flying

NASA photos version (left). His innovation has saved billions of dollars in fuel costs.

study team in 1945 had added to such beliefs. Whitcomb’s discovery enabled the Air Force’s transonic force structure that was subsequently deployed for the Cold War and beyond. Proof that Area Rule also restored NACA to the service’s good graces was evident in Whitcomb’s receiving of the Air Force Exceptional Service Medal. Whitcomb was not content to rest on this single laurel. Called into the

increasing its fineness ratio—the ratio redesigned to conform to of its length to its width. Area Rule principles with Whitcomb broached this “rule of a lengthened fuselage and thumb” at the next NACA Langley also modified wing leading technical seminar. After he finished, edges, returned to Edwards Busemann rose to his feet. “Some in 1954, handily accelerat- people come up with half-baked ideas ing through the speed of and call them theories,” he said. “Whit- sound. comb comes up with a brilliant idea Whitcomb’s Area Rule and calls it a rule of thumb.” had added 25 percent more A landmark, confidential NACA re- speed to the design. search memorandum issued in Septem- Area ruling also re- ber 1952 was the result of comprehen- shaped the Navy’s F9F-9, sive wind tunnel testing that followed. which became the supersonic F11F-1 The memo’s prosaic title—“A Study Tiger, and Vought’s F8U-1 Crusader. early design conferences for a pro- of the Zero-Lift Drag-Rise Charac- It added sinuous curves to Republic’s posed supersonic civil air transport, teristics of Wing-Body Combinations F-105 Thunderchief, McDonnell’s he returned to transonics when SCAT Near the Speed of Sound”—belied its F4H-1 Phantom II, and Northrop’s tiny studies grew ever more complex and revolutionary implications. N-156, which spawned the T-38 Talon improbable. At just over 30, using a mix of trainer and the F-5A Freedom Fighter. “I said, ‘I’m going to quit the field,’ ” intuition, experimentation, and bor- he recalled in 1973. “‘I’m going back rowed theoretical analogy, Whitcomb Uncorking No. 2 where I know I can make things pay had reshaped the airplane. Area Rule Whitcomb received the 1954 Collier off,’ and I went back to the region right was—next to the swept and delta wings Trophy “for discovery and experimen- near the speed of sound.” Shortly after, themselves—the most significant and tal verification of the Area Rule, a he uncorked his second great idea, the most visible manifestation of transonic contribution to base knowledge yield- “supercritical wing.” design. ing significantly higher airplane speed The supercritical wing had a largely Nicknamed “Coke Bottle” and “Wasp and greater range with same power.” flattop airfoil cross-section with its Waist,” Area Rule came just in time for He had also redeemed the reputation camber (curvature) well aft. It raised the F-102. Weeks before its first flight, of the NACA with the Air Force. Since the wing’s critical Mach number—the Convair engineers had learned from 1941, when Gen. Henry H. “Hap” point where the accelerated airflow NACA tunnel tests that the F-102 likely Arnold had been surprised to learn over the wing creates a shock wave. would not exceed the speed of sound. that Britain was more advanced in the A jetliner cruising at Mach 0.82 with Whitcomb’s confidential memo- field of jet propulsion, the agency had a conventional wing might, with a su- randum came afterward, followed faced criticism for technological com- percritical one, cruise at Mach 0.86 or shortly by the first F-102’s disastrous placency. The appearance of German even higher for the same expenditure performance in the skies over Edwards. jets, the V-2 missile, and discovery of of fuel. While this idea was exciting For Convair it was, literally, back advanced German high-speed research enough, it became one of vital stra- to the drawing board. The F-102, by Theodore von Karman’s technical tegic significance for both military AIR FORCE Magazine / February 2010 71 not the first to experiment with some sort of endplates located on wingtips, NASA photo Whitcomb employed greater insight and intuition than his predecessors. He developed a deceptively simple- looking fin that could reduce a trans- port’s drag by a fifth. But would it work? Tests in 1979 using a Boeing KC-135 Stratotanker loaned to NASA proved that winglets functioned better at reduc- ing drag and increasing lift than merely extending an airplane’s wingspan. The winglets increased its range by seven percent and revealed the power of the invisible vortices: The KC-135 returned from one flight with a winglet bent in a half-circle, a testimony of the strength and energy contained within the small horizontal tornadoes. Since the late 1980s, winglets have become ubiquitous, visible to anyone living near an airport offering commer- cial and business jet aircraft service. The general aviation and business airplane communities were the first A swing-wing Transonic Aircraft Technology (TACT) F-111A configured with Whit- to incorporate winglets, just as they comb’s supercritical wing. It delivered 50 percent better lift than the standard were the first to adopt his supercriti- F-111A. cal wing. In 1979, Learjet introduced the Longhorn, a winglet-equipped and airline operators in the oil crises McDonnell Douglas YC-14 and YC- series of its famed business jet aircraft. of the 1970s. 15 Advanced Medium Short Takeoff Gulfstream added them to its own line Early tests on a modified trainer and Landing Transport test beds. It of business aircraft, and later Boeing encouraged NASA to move to higher- was evaluated for fighter and attack and McDonnell Douglas adapted them Mach trials using an ex-Navy Vought aircraft applications on a modified F- for the 747-400 series jumbo jet and TF-8A Crusader jet fighter. Flight tests 111A as part of the joint NASA-Air the MD-11. began in 1971, and quickly demon- Force Transonic Aircraft Technology Winglets were incorporated on the strated that the anticipated benefits of (TACT) program, as was a supercritical C-17 airlifter, together with a super- the wing were correct. The modified spin-off, the Mission Adaptive Wing. critical wing. The combination gives F-8 had 15 percent better transonic The TACT F-111A had 50 percent the C-17 better range and speed than performance than a standard Crusader. more lift during maneuvering than a would have been possible had it used Tests indicated commercial airliners standard F-111A. a larger, conventional planform. with supercritical wings would be more Building upon the earlier flight-test Whitcomb retired from NASA in profitable than ones with conventional experience of the YC-15 program, and 1980, convinced that no large chal- wings, saving the airline industry $78 continued and lengthy wind tunnel lenges in aviation remained. Thereafter, million per year in 1974 dollars— studies at NASA and elsewhere, the he turned his interests toward broader equivalent to $342 million today. McDonnell Douglas C-17A Globemas- questions in the physical sciences. In 1969, Whitcomb received NASA’s ter III transport went a step further. It Asked in 2003 whether he advised Exceptional Scientific Achievement featured not only a supercritical wing, young people to follow his footsteps, Medal. Four years later, President Nixon but another Whitcomb innovation—the he replied, “I shock people. I say if awarded him the National Medal of wingtip winglet. you want to make an impact or have Science. In 1974, Whitcomb received an effect, don’t go into aeronautics. It’s a $25,000 cash award for inventing the “I Shock People” pretty well stabilized. No big things supercritical wing, and later that year, The winglet constituted the third of have come up in aeronautics since my the National Aeronautic Association his innovations and was even more read- inventions, and it has been 20 years awarded him the 1974 Wright Brothers ily visible than area ruling. Aerodynam- since I left.” Memorial Trophy. icists had long recognized that swirling If many might disagree, most would The supercritical wing was very wingtip vortices, a byproduct of the concur that it will take an extraordi- quickly applied to a range of com- airflow’s circulation around the wing, nary breakthrough to match any one mercial aircraft, beginning with the constituted a source of performance- of his remarkable trio of transonic Rockwell Sabreliner 65, the Canadair robbing turbulence and drag. While accomplishments. n Challenger, and the French Falcon 50 business jet aircraft. Richard P. Hallion is an aerospace historian who served 11 years as the Air Force It had clear military value, and so Historian and has written widely on aerospace technology and airpower topics. was incorporated on the Boeing and This is his first article for Air Force Magazine. 72 AIR FORCE Magazine / February 2010