The inventions, institutions, gadgets, and lucky breaks that have shaped the story of the airplane.
- By Roger Bilstein
- Air & Space magazine, March 2003
(Page 2 of 3)
Meanwhile, airlines began to pay more attention to consumer complaints, pressuring manufacturers to design cabins that were quieter, heated, and equipped with lavatories. When United Aircraft and Transport placed an order in 1932 for a fast new airliner, Boeing responded with the model 247, a streamlined, low-wing, twin-engine monoplane with retractable gear. Its design featured stressed-skin construction. Its engines were powerful new Pratt & Whitney Wasp radials, each housed in a NACA cowling. And it had a heated cabin, seats (each with individual air vents) that featured quality upholstering and mounts to reduce vibration, and a full-service lavatory, complete with mirror (one engineer argued against it on the basis of weight, adding that men didn’t need mirrors and women always carried their own).
Boeing showcased its 247 in the Travel and Transport Building at Chicago’s 1933 Century of Progress Exposition, where it created a sensation as an icon of 20th century transport technology. Wide-eyed visitors clambered up a catwalk over the wing, past the cockpit, and down again to encounter an actual Wasp engine. But the 247 carried only 10 passengers. Receiving a competing order from Transcontinental and Western Air, Douglas Aircraft included all of rival Boeing’s features plus an improved NACA cowling and better streamlining, bigger engines, and variable-pitch propellers, none of which were available on the first production models of the 247. The DC-1 looked so promising that Douglas immediately developed a speedier, improved version, the DC-2, which offered 14 seats—nearly half again as many as the 247. In 1934, a DC-2, casually flown by pilots for the Dutch carrier KLM, nearly beat the Comet, a customized deHavilland twin-engine speedster, in the MacRobertson race, from England to Australia. The Douglas design became an international phenomenon and started the company on a stretch of industry dominance that was to last 30 years.
C.R. Smith, impresario of American Airlines, wanted an even bigger, faster version of the DC-2. A fuselage that was enlarged to accommodate railroad-style sleeper berths morphed into a 21-passenger “dayliner”—the inimitable, indomitable DC-3, which entered service in 1936. With improved engines, twice the passenger capacity of the 247, and an extremely cost-efficient design, the DC-3 flew into aeronautical immortality. Along with its larger, four-engine successors, the DC-3 had wing flaps for added lift during takeoff and landing. By the early 1940s, even larger airliners appeared with pressurized cabins, tricycle landing gear, improved de-icing equipment, autopilot systems, and other technologies that enhanced passenger comfort and safety as well as aircraft reliability and efficiency. By 1943, the Lockheed L-049 Constellation, with its distinctive triple vertical tail, epitomized the era of modern airliners that transformed both wartime air transport and postwar airline transportation.
While enormous strides were being made in fixed-wing design, by the late 1930s Russian émigré Igor Sikorsky had perfected the prototype of the modern helicopter, with a powered rotor overhead to provide both lift and forward thrust and a tail rotor to counteract the main rotor’s torque. The helicopter’s unique ability to hover and its performance in the Pacific theater of World War II won wider acceptance for the rotorcraft, and this was followed by their dramatic success in evacuating casualties during the Korean War in the 1950s.
During the decades of the 1920s and 1930s, as Sikorsky was fleshing out his ideas, a host of suppliers, vendors, and institutional organizations appeared—forming an infrastructure essential to supporting a growing industry. Traditional manufacturers like Westinghouse, AC Spark Plug, Bendix, Standard Oil, and others moved into the flying game. In the late 1920s, Edwin Link scrounged some bellows, push rods, and linkages from his father’s pipe organ company and built a usable flight simulator. At first, only amusement parks showed much interest, but by the late 1930s, the threat of war triggered a surge of military orders. EDO Corporation, named for Earl Dodge Osborn, started to build pontoons for floatplanes in 1925. As a diversified aerospace supplier, EDO continued to flourish in the following years as a fabricator of such military products as under-wing pylons that carry fuel tanks and assorted ordnance. In 1923, Osborn helped launch Aviation magazine, and served as its publisher until he sold it to McGraw-Hill in 1929.The periodical eventually became Aviation Week & Space Technology, the premier source for aerospace news. In 1933, a professional society of engineers organized as the Institute for Aeronautical Sciences and later became the American Institute of Aeronautics and Astronautics. Businesses and organizations like these proved invaluable in meeting crucial challenges of World War II.
Props hit a wall
But aircraft had hit a speed limit. Propellers were limited at high speeds because when their blades moved at supersonic speeds, they lost thrust. A few mavericks began to consider alternative power plants, including gas turbines. In England, Frank Whittle initiated a dogged research program in the face of nearly universal skepticism—until 1937, when he demonstrated a design that compressed air by spinning it centrifugally. The path of technological evolution in one community can often be plotted in other, equally capable research-and-development groups. Working with no knowledge of Whittle’s work, Hans von Ohain, a German, developed a similar engine that powered the first jet airplane, the Heinkel He 178, which flew in 1939. Research in the United States into the new propulsion technology languished despite the fact that a related technology had proved successful: turbosuperchargers.
In April 1941, when U.S. Army Air Forces General Henry “Hap” Arnold paid a visit to England, he was startled to learn of a prototype jet—the Gloster E28/39—then undergoing taxi tests. An irritated Arnold returned home, asking pointed questions about the U.S. aviation community’s obvious lack of progress in jet propulsion. In the end, concerned that the technology would fall into German hands, the British furnished U.S. industry with a Whittle engine, blueprints, and eventually a visit by Whittle himself to explain how everything worked. General Electric won the contract to construct modified versions of the Whittle jet engine. These early turbojets powered the first U.S. combat jets, such as the Lockheed P-80 Shooting Star and the Grumman F9F Panther. Later in the war, Germany developed the more successful axialflow jet engine—its compressor used propellerlike vanes to drive the air in a straight path along the axis of the engine. During the course of Operation Paperclip, which the United States mounted at war’s end to harvest advanced German research and key personnel, much of this technology arrived on U.S. shores, where it provided the foundations for similar American designs and became the configuration used in all modern jet engines.
In addition to jet engines, German legacies included significant verification of the viability of swept-back wings. During World War II, high-performance fighters in 500-mph dives began to encounter severe—and sometimes disastrous—aerodynamic buffeting. Wind tunnel tests revealed that shock waves appeared on aircraft surfaces at about Mach 1—the speed of sound. Some aerodynamic adjustments helped—Lockheed gave the P-38 a set of dive flaps to recover the craft from the Mach effect—but fliers also simply had to avoid excessive speeds. In the postwar era, as jet engines led to designs for even faster aircraft, understanding and coping with what came to be called the “sound barrier” became a paramount challenge. Some aerodynamicists had been thinking about this problem since German researcher Adolph Busemann presented a paper in 1935 at a Rome conference on high-speed flight. Busemann said that when exposed to shock waves trailing from the airplane’s nose at very high speeds, an “arrow” wing would produce less drag than a straight wing. Airplanes of the mid-1930s flew too slowly to encounter sonic buffeting, so his paper received little attention until German aircraft with jet and rocket engines entered service during World War II.