The Airplane - Jay Spenser [53]
In January 1933, Adolf Hitler became chancellor of Germany. Across the Atlantic, Franklin Delano Roosevelt, Hitler’s antithesis, took office in March as president of the United States. That year in New Deal America, the chocolate-chip cookie was invented, Prohibition was repealed, and history’s first two modern commercial airliners took to the skies.
The first modern passenger airliner, the sleek and fast Boeing 247, shaved eight hours off the transcontinental flight time of the era’s Fords and Fokkers. The 247 carried ten passengers and a crew of three plus baggage and 400 pounds (180 kilograms) of airmail or freight. In an era of cumbersome, ungainly airliners—including Boeing’s own fabric-covered Model 80A trimotor biplane—it crossed the United States in twenty-one hours westbound and just nineteen flying east with the prevailing winds.
The Boeing 247 was an all-metal semi-monocoque monoplane with a fully cantilevered low wing and two engines. It also featured a retractable landing gear, an autopilot to reduce pilot workload, gyroscopic instruments for night and bad-weather operations, and deicer boots to shed ice from its wings and tail in flight.
The structural heart of this astonishing transport plane was a wing with built-up metal spars reinforced by bridge-like diagonal members in a configuration known as the Warren truss. Riveted aluminum sheeting surrounded this structure, locking it together and sharing the structural loads. The resulting wing was clean, light, and strong.
In a bold move to update its entire fleet, United Aircraft and Transport Corporation (today United Airlines) ordered fifty-nine Boeing 247s. This tied up at least the first year’s production, forcing United’s competitors to look elsewhere.
Needing to replace its discredited Fokkers and dowdy Fords, Transcontinental and Western Air solicited bids from five companies for a new high-performance trimotor. Douglas Aircraft of Santa Monica, California, accepted the challenge but proposed instead a twin-engine design more advanced than Boeing’s.
Even as the Boeing 247 flew in February 1933, Douglas was building this all-metal semi-monocoque airliner. The twelve-passenger DC-1 (DC for “Douglas Commercial”) flew that July and went on to set many records. Before placing this design into production in 1934, however, Douglas stretched its fuselage to accommodate one more row of seats. The result was the DC-2, which carried fourteen passengers.
Although first to market, Boeing’s 247 found only limited commercial success because it simply carried too little payload to exploit the potential of its new technology. The Douglas DC-2 did somewhat better, offering incrementally greater speed, comfort, and range as well as 40 percent more passenger capacity. Moreover, the DC-2 offered the advantages of a higher wing loading.
Wing loading is the loaded weight of the airplane divided by the area of its wings. An important design parameter, it largely determines an airplane’s capabilities. Those with low wing loadings (for example, old biplanes and modern light airplanes) need less installed power to achieve flight and operate at lower speeds. In contrast, high-wing-loading designs (jetliners and jet fighters, for instance) require more power and fly much faster.
Igor Sikorsky’s Ilya Muromets of 1914 provides a good example. It had the wingspan of a World War II Boeing B-17 bomber and roughly the equivalent wing area. However, the Sikorsky also had just one-eighth the engine power of a B-17. Consequently, the Ilya Muromets needed a much lower wing loading to achieve flight. With a gross weight one-fifth that of the B-17, the Ilya Muromets also had about one-fifth the wing loading, which greatly limited its speed and payload. This comparison illustrates why the best World War I airplanes pale in comparison to those of World War II, and why today’s high-performance military machines in turn far outstrip