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Four-Engine Bomber

In the summer of 1935, the Boeing Airplane Co. unveiled its Model 299, a remarkable four-engine, high-speed, long-range, heavy bomber which was eventually designated the B-17 Flying Fortress. This plane, although destined to change the complexion of aerial warfare, initially failed to convince the Army's General Staff of its merits and capabilities. As a result, the General Staff directed that the major portion of funds for the purchase of bombers be spent for cheaper two-engine Douglas B-18s, rather than more costly four-engine B-17s, believing the latter type an expensive and unnecessary luxury. 

Proving the Flying Fortress
As a result of the General Staff's decision, only 13 YB-17s and one YB-17A were ordered by mid-1937 as compared to 133 B-18s and 177 B-18As. The Air Corps was determined to prove the value of the four-engine B-17 with this handful of service test planes. It flew its YB-17s at every opportunity over the U.S. and even scheduled good will flights to South America to demonstrate the long-range capabilities of the plane. It eventually proved its point, and by the end of 1938, contracts for 39 additional B-17Bs were awarded. In addition, a new four-engine bomber, the Consolidated XB-24, was ordered on March 30, 1939. At the time World War II began in Europe in September 1939, the first B-17Bs were beginning to come off the production line. 

Pre-war Super Bombers
Although the Boeing B-17 was to gain greater fame, Boeing also designed and built an even larger four-engine bomber in the mid-1930s, the XB-15. Its design was actually begun before the B-17, but it did not make its first flight until 1937, more than two years after that of the B-17. With a wingspan of 149 feet, almost half again as large as the B-17, the XB-15 was the victim of lag in engine development -- there were simply no engines available which were powerful enough to give it the performance it deserved. Numerous test projects were made with the XB-15, but in 1943 it was relegated to the role of a cargo airplane and redesignated the XC-105. At the end of World War II, it was dismantled in Panama.

Douglas became involved with the super-bomber in 1935 when it began design of an enormous airplane having a 212-foot wingspan and a tricycle landing gear. Designated the XB-19, it made its first flight on June 27, 1941. Like the XB-15, the XB-19 was underpowered, and after numerous test projects were conducted with the plane, it also began carrying cargo. During WWII, its Wright radial engines were replaced by Allison in-line engines of greater power, but by the end of the war, bomber technology had far outdistanced the XB-19, making further development of the plane uneconomical. In 1949 the XB-19 was reduced to scrap metal at Davis-Monthan Air Force Base, Ariz.

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