The Man Who Put the Squeeze on Aircraft Design

Jan. 1, 1956
In Washington, D. C. last month, Richard Travis Whitcomb, a thirty-four-year-old National Advisory Committee for Aeronautics engineer, was awarded the Collier Trophy, one of the nation’s highest honors for achievement in the field of aviation. Whitcomb was also honored by the Air Force when, on December 16, AF Secretary Donald Quarles presented him the Exceptional Service Medal. Whitcomb’s achievement: development of the concept of the “Area Rule,” commonly referred to as the “Coke-Bottle” or “Wasp-Waist” shape, which has added more than 100 mph to the speed of several jet aircraft now flying, and provided the real key to serious drag problems encountered in transonic flight. The Area Rule, which really ought to be renamed the “Whitcomb Rule,” is being hailed by aviation leaders as the greatest advancement in aviation since the beginning of the jet age.

For Whitcomb, discovery of the Area Rule was not an accident. It was the culmination of at least fifteen years of hard work, undivided attention, and an intensive drive to make a name for himself in aeronautical engineering. The eldest of four children of a teetotaling mathematician-engineer, Kenneth F. Whitcomb, Dick Whitcomb was born in Evanston, Ill., and grew up in Worcester, Mass. Before he was ten, Whitcomb, a quiet-mannered, shy boy, had charted his life’s course: he would be an engineer—not a theoretician or “book” man like his father, and his grandfather, but a practical engineer who would invent things. He had been impressed by the fact that his grandfather kept on man on the payroll for the sole purpose of “getting ideas.”

Dick shunned the traditional ways of boyhood in Worchester—playing football, baseball, ice hockey, or chasing girls. He was interested only in tinkering with mechanical objects, or reading books on engines and engineering. Before long, he had converted the Whitcomb basement into a home workshop, complete with lathes, presses, grinders. To light his subterranean laboratory, engineer Whitcomb, then ten, conceived and built a bowl-shaped reflector, with scores of mirrors, and placed it outside the basement window. It was the marvel of the neighborhood.

Soon, weird objects begin to flow from Whitcomb’s assembly line. The first were improvements on his own toys. For example, unable to buy a roundhouse turntable for his electric train, Whitcomb built one. He improved a toy motor boat, powered by a can of Sterno. At the age of twelve, Whitcomb set about to improve the rubber band system which powered his model planes. By mathematics, he figured that he could get twice as much power by stretching the rubber than twisting traditional fashion. Accordingly, he designed a built an elaborate motor, employing pulley, gears, long shafts, and other paraphernalia, which stretched, rather than twisted, the rubber. It was a good system—on paper—but it didn’t work.

All through public high school in Worchester—much to his parents’ consternation—Whitcomb stuck close to his workshop. Once, under great pressure, he consented to take dancing lessons. But the experience was painful—enough to send him scurrying back to the lab. He did join the Boy Scouts (in which he advanced to the rank of Star) and was active in social work at the Congregational Church. He took one brief fling at gardening but his main interest was in building and tinkering. His models of planes and stage coaches won him prizes and money (on the basis of which he figured his work was worth ten cents an hour.) When the mainspring on his wrist watch broke, he took out the broken piece, then reinserted the shortened spring. The watch ran fine except that it had to be wound every twenty hours instead of twenty-four.

Whitcomb’s interest in aviation developed to the point where all of his part-time work was devoted exclusively to it. He built original-design models by the score, and even converted part of his basement workshop to selling supplies—so that he could get his materials wholesale. But, oddly, Whitcomb never cared much for flying. He once briefly tried out in a Link Trainer, but, he says: “I didn’t have confidence in myself. I had a lot of trouble in take-offs and landings.” One of his model-building friends learned to fly and took Whitcomb on his first ride in a small Taylorcraft. When they got back on the ground, Whitcomb was pale, and he asked nervously: “Why did you have to bank so hard.”

In 1939, Whitcomb entered Worchester polytechnic Institute, where, not surprisingly, he majored in aeronautical engineering. He worked summers as a lathe operator and, in his home workshop at night, began design studies on a guided bomb. Whitcomb declined invitations to join social fraternities, but was elected to the school’s Tau Beta Pi honorary society, and joined Sigma Xi, the scientific fraternity. After graduation in 1943—with “high distinction—Whitcomb took a Civil Service job with NACA’s Langley Aeronautical Laboratory at Langley AFB, VA There he was astonished to find skilled engineers testing a hush-hush wind tunnel version of a heat-seeking guided bomb, similar to the one he designed. (Test showed the bomb had severe limitations and it was later dropped from the program.)

Assigned to Langley’s High Speed Wind Tunnel, young Whitcomb quickly established himself as a “comer.” After a few months’ indoctrination, he was put to work on some of NACA’s most important work—efforts to increase range and speed of World War II fighters.

Whitcomb took a $60-a-month apartment in Hampton, Va., where he still lives, and ate his meals at Mrs. Mann’s boarding house nearby. Following his life-long pattern, he declined social functions in favor of remaining home to work on his inventions. In a vacant field near his apartment, Whitcomb built a fairly elaborate workshop, and was soon drawing plans for a helicopter and a jet-powered vertical take-off airplane.

In the meantime, laboratory work in NACA’s wind tunnel began to absorb Whitcomb’s attention. Particularly fascinating to the youthful engineer were the problems of high-speed drag.

Drag, stated in simplest terms, is the resistance set up by air when a body attempts to move through it. You can feel it yourself by putting your hands out of the window of a moving automobile. One obvious way to reduce drag is to streamline the plane—“clean it up”—enclose the cockpit, engines, even sweep back the wings. Such streamlining immeasurably helped subsonic planes. But when airplanes began flying at near sonic speeds, nautical engineers, including Whitcomb, found that aircraft were impeded by a new kind of drag—that caused by shock waves.

At subsonic speeds, an airplane in flight literally telegraphs its approach. It projects an impulse—at the speed of sound—and the air ahead is pushed aside, or disturbed by these impulses, and the plane flies into this disturbed air with relative ease. But when a plane flies at the speed of sound, it travels as fast as the impulses, and therefore the air ahead has no chance to “get ready,” or move out of the way. The result is that, in order for the plane to get through, the air must move aside violently. This violent pushing aside of the air causes shock waves. At exactly the speed of sound, these waves—one on the plane’s nose, one on the wing and one behind the wing caused by the speed-up of air over the wing airfoil—move out from the plane in a great circle. “If the shock waves were visible,” says Whitcomb, “the planes would look as if it were flying straight through the middle of a gigantic phonograph record.”

The forces acting in and around these shock waves create enormous drag, and slow the plane down. The waves are especially bothersome in the transonic range, from roughly Mach 1.2. (At higher speeds, the sonic waves, outpaced by the supersonic plane, bend back.) For years, aeronautical engineers—through mathematical theories and actual wind tunnel observations—had been aware of the phenomenon, and they thought they had it measured accurately, simply by adding the drag of the wing to the drag of the fuselage. It was just a question of waiting for the development of engines with sufficient thrust to overcome it. But when engines were developed with thrust which—theoretically—could overcome shock wave drag, everybody came in for a big surprise—the planes still would not fly as fast as actual fact as they would in theory. Convair’s delta-wing F-102, for example, was designed with sufficient thrust to make it fly supersonically—ion spite of shock wave drag. But in actual flight, the F-102 “stuck” at Mach .98, just short of the speed of sound.

At first it was thought that the Convair plane was a “bad design.” But then other planes got “stuck”—either in flight or in wind tunnel tests. Some actually penetrated the sonic barrier—using afterburners or rockets for every ounce of thrust—but only for brief periods, because of high fuel consumption. This perplexing problem became more than simply an interesting aerodynamics phenomenon: the safety of the nation was at stake, for our jet fighters were not performing as well as expected. What could be done

In 1951 at Langley, Whitcomb, working closely with his boss, Axel Mattson, set to work. They had one very good tool: Langley’s brand-new transonic wind tunnel—the first in the world. Actually the tunnel itself was something of an engineering marvel. NACA had several subsonic and supersonic tunnels, but construction of a transonic tunnel had been seriously questioned due to severally knotty aerodynamics problems that occur at transonic speeds. However, these problems were overcome by another NACA scientist, John Stack, and the decision was made to go ahead. Stack himself won a Collier Trophy for his ingenious work on the tunnel. It is fortunate that the decision was made to build the tunnel for, without it, Whitcomb might never had made his historic discovery of the Area Rule.

Working in the tunnel, with a variety of shapes and models, Whitcomb began to observe and calculate high-speed drag effect—particularly shock-wave drag effect. He would figure mathematically according to accepted theories—what the drag effect should be, then he would put the models inside the tunnel and make actual tests—with schlieren photographs (a process by which shock waves can be shown photographically). But Whitcomb discovered a great discrepancy. In actual tests, the models rarely matched theoretical drag. Here was a discovery to excite an engineer’s imagination! When some of the scientist protested Whitcomb’s methods, he said: “To hell with books and theories, we’re going to do this by look and by feel.”

After months of tests, working day and night, Whitcomb concluded that the way engineers had been computing transonic drag was incorrect. They had been underestimating, Whitcomb said. It was not accurate he postulated, to simply add drag of the fuselage and drag of the wing and come up with total drag. In his tests he noticed that there was an interrelation between the position of wing and fuselage and other items, such as engine nacelles. By shifting positions, or altering the combined mass, he discovered the drag total varied significantly. In short, Whitcomb said, the drag of the plane may be computed as a whole, not the sum of the parts.

Having discovered why drag was so much greater than previously believed, Whitcomb went one step further and tried to come up with something—other than waiting for engines with greatly increased power—to overcome it. He built many more models, some with “ideal shapes,” or a model that would give minimum drag, according to his new concept of it. He plotted the cross-sectional areas of all the shapes graphically, and compared the ideal shapes with a graphic plot of several actual planes—including the Convair F-102. Whitcomb discovered that the F-102, as well as all other planes he tested, were different in area from his ideal shape. They “violated” what he called the “Area Rule.” In other words, they had the area humped in the wrong place.

Going further, Whitcomb theorized that if the shape of the airplane could be altered so that the “areas” came as closely as possible to matching the “ideal areas,” the drag would be significantly reduced. Taking models of actual planes, Whitcomb squeezed the fuselage of those that had too much area near the wing. In other cases, he “bulged” the areas ahead and behind the wing. His experiments confirmed that the drag was indeed reduced—in some cases as much as twenty-five percent. In must instances, the middle shock wave over the plane was eliminated almost entirely. In further tests he discovered that by lengthening the nose or the tail of the plane—getting closer to the ideal area plot —he reduced drag even further.

When Whitcomb presented his theories to aviation companies he first met with some skepticism. But when the Convair F-102 in actual flight stuck at Mach .98, Convair engineers took notice. They courageously decided to design the F-102. To keep from “violating” the Area Rule, they squeezed some area out of the fuselage in the region of the wing. The result has been variously called the “Pinch-Bottle,” “Coke-Bottle,” “Marilyn-Monroe,” or “Wasp-Waist” shape. Convair also lengthened the F-102’s fuselage, added some area to the rear of the wing. The new plane, called the F-102A, zoomed through the sonic barrier on its first flight—while climbing. Tests showed drag had been reduced in the transonic zone by nearly twenty-five percent. The new shape had added more than 100 mph to the speed of the plane, without increasing fuel consumption.

At about the same time, Grumman engineers were working up a new Navy plane, the F11F-1 Tiger. They were informed of Whitcomb’s theory and visited him at Langley. Soon they were reshaping the F11F-1 in order not to violate the Area Rule. The Grumman plane then became the first aircraft to try out the new principle in actual flight and flew faster than sound on a level course. The same took place with Chance Vought’s F8U. Other companies took Whitcomb’s theories to heart, when it was recognized that the Area Rule was the real key to practical supersonic flight. It would seem logical to assume that the new aircraft coming along will incorporate the area rule, such as the Convair B-58, North American’s F-107 (advanced version of the F-100) and Republic’s F-105 supersonic fighter-bomber. Canadair recently announce it had applied Are Rule to the Canadian version of the F-86 Sabrejet. Today every design study submitted to the military must be accompanied by an Area Rule graph.

During the last four years, most of Whitcomb’s time has been consumed by his work on his new theories. Lately, however, his associates, with some gratification, had noticed dramatic changes. He has acquired a sailboat, and is even thinking of taking up duck hunting. He was recently elected President of “The Singleton’s Club,” an organization in Hampton, made up of about 150 bachelors who would like to meet eligible young ladies. But the most Whitcomb says, with some apprehension: “A man has to be successful before he gets married. We have a lot of work to do here yet.” His next job: applying the Area Rule to Mach Two and Mach Three aircraft.

About the Author: Clay Blair, Jr., the Pentagon correspondent for Time and Life, was born in Lexington, VA, in May 1925. During World War II, he spent almost two years in the submarine service and participated in war patrols against the Japanese. After the war, he attended Tulane and Columbia Universities and joined Time-Life in 1948. He has authored The Atomic Submarine and Admiral Rickover (1954), Beyond Courage (1955), and co-authored (with James R. Shepley, Time’s Washington Bureau Chief) The Hydrogen Bomb (1954). Part of his latest book (Beyond Courage), was reprinted in three installments in Air Force beginning in June 1955. He lives with his wife, the former Agnes Kemp Devereux, and their children in a Washington suburb. He enjoys jazz and water skiing.