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The Boeing Model 247 was an early United States airliner, considered the first such aircraft to fully incorporate advances such as all-metal (anodized aluminium) semimonocoque construction, a fully cantilevered wing and retractable landing gear.〔("Model 247 Commercial Transport." ) ''boeing.com,'' 2009. Retrieved: June 14, 2010.〕〔van der Linden 1991, (pp. xi–xii ).〕 Other advanced features included control surface trim tabs, an autopilot, and de-icing boots for the wings and tailplane.〔Bryan 1979, p. 110.〕 "Ordered off the drawing board", the 247 first flew on February 8, 1933 and entered service later that year.〔 Subsequently, development in airliner design saw engines and airframes becoming larger, and four-engined designs emerged, but no significant changes to this basic formula appeared until cabin pressurization and high altitude cruise were introduced in 1940 with the first pressurized airliner, the Boeing 307 Stratoliner.〔Gould 1995, p. 14.〕 ==Design and development== Boeing had eclipsed other aviation manufacturers by introducing a host of aerodynamic and technical features into a commercial airliner. This advanced design, which was a progression from earlier Monomail (Models 200, 221, 221A) and B-9 bomber designs, combined speed and safety. The Boeing 247 was faster than the U.S. premier fighter aircraft of its day, the Boeing P-12, which was an open-cockpit biplane.〔Serling 1992, p. 19.〕 Yet its flight envelope included a rather docile landing speed, which precluded the need for flaps, and pilots learned that at speeds as low as , the 247 could be taxiied "tail high" for ease of ground handling.〔Seely 1968, p. 58.〕 In addition, the 247 was the first twin-engined passenger transport able to fly on one engine. With controllable pitch propellers (standard equipment on the 247D), the 247 could maintain 11,500 ft at maximum gross takeoff weight.〔Seely 1968, p. 56.〕 Its combination of features set the standard for the Douglas DC-1 and other airliners before World War II.〔 Originally planned as a 14-passenger airliner powered by Pratt & Whitney R-1690 Hornet radial engines, the preliminary review of the design concept by United Air Lines' pilots had resulted in a redesign to a smaller, less capable design configuration.〔Serling 1992, p. 20.〕〔Fernandez 1983, pp. 74–78, 104–105.〕 One concern of the pilots was that no airfield then in existence, in their view, could safely take an eight-ton aircraft.〔 They also objected to the use of Hornet engines because most pilots were accustomed to the less-powerful Wasps and would find Hornets overpowering. Pratt & Whitney's chief engineer, George Mead, knew that this thinking was misguided and that within a few years it would seem antiquated.〔 P&W's president, Frederick Rentschler, faced with a tough decision, decided to acquiesce to the airline pilots' unanimous demand. The decision created a rift between Mead and Rentschler.〔 Despite the bitter disagreements on design and engines, the 247 was still a remarkable achievement and was Boeing's showcase exhibit at the 1933 Chicago World's Fair.〔Serling 1992, p. 22.〕 The cockpit windshield of the first 247s was angled forward, instead of the conventional aft sweep. This was the design solution (similar to that adopted by other contemporary aircraft that used a forward-raked windscreen) to the problem of lighted control panel instruments reflecting off the windshield at night, but it turned out that the forward-sloping windshield would reflect ground lights instead, especially during landings, and it also increased drag slightly.〔Pearcy 1995〕〔van der Linden 1991, (p. 93 ).〕 By the introduction of the 247D, the windshield was sloped aft in the usual way, and the night-glare problem was resolved by installing an extension (the ''glarescreen'') over the control panel.〔Holcomb, Kevin. ("The Boeing 247." ) Airminded.net webpage showing initial and final windshield angles and glarescreen installation in the 247D, 2009. Retrieved: July 26, 2009.〕 Boeing considered safety features highly, building in structural strength as well as incorporating design elements that enhanced customer comfort and well-being, such as the thermostatically-controlled, air conditioned and soundproof cabin. The crew included a pilot and copilot as well as a flight attendant who could tend to passenger needs.〔van der Linden 1991, (p. 1 ).〕 The main landing gear did not fully retract; a portion of the wheels extended below the nacelles, typical of designs of the time, as a means of reducing structural damage in a wheels-up landing. The tailwheel was not retractable. While the Model 247 and 247A had speed-ring engine cowlings and fixed-pitch propellers, the Model 247D incorporated NACA cowlings and variable-pitch propellers.〔("Boeing Model 247: First modern airliner." ) ''acepilots.com'', 2007. Retrieved: July 26, 2009.〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Boeing 247」の詳細全文を読む スポンサード リンク
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