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The Douglas A-26 Invader (designated B-26 between 1948 and 1965) is a twin-engined light bomber and attack aircraft that was built by Douglas Aircraft Company during World War II which also saw service during several major Cold War conflicts. A limited number of highly modified United States Air Force aircraft served in Southeast Asia until 1969. It was found to be a fast aircraft capable of carrying twice its specified bomb load. A range of guns could be fitted to produce a formidable ground-attack aircraft.〔Wheeler 1992, p. 82.〕 The postwar re-designation of the type from A-26 to B-26 has led to popular confusion with the Martin B-26 Marauder which first flew in November 1940, some 16 months before the Douglas design's maiden flight. Although both types were powered by the widely used Pratt & Whitney R-2800 Double Wasp eighteen-cylinder, double-row radial engine, they were completely different and separate designs — the Martin bomber originated in 1939, with roughly twice as many Marauders (nearly 5,300) produced in comparison to the Douglas design. The last A-26 in active U.S. service was assigned to the Air National Guard; that aircraft being retired from military service in 1972 by the U.S. Air Force and the National Guard Bureau and donated to the National Air and Space Museum. ==Design and development== The A-26 was not unusual for an attack bomber of the early 1940s in having a single pilot. Designed by Ed Heinemann, Robert Donovan, and Ted R. Smith,〔Francillon 1979〕 its innovative NACA 65-215 laminar flow airfoil wing was the work of project aerodynamicist A.M.O. Smith.〔Smith, A.M.O., "High-Lift Aerodynamics; the 37th Wright Brothers Lecture", AIAA paper 74-939, reprinted in the ''AIAA Journal of Aircraft'', Vol. 12 No. 6, June 1975.〕〔Lednicer, David. (''The Incomplete Guide to Airfoil Usage.'' ) Champaign, Illinois: UIUC Applied Aerodynamics Group, 2010. Retrieved: 18 May 2011〕 The Douglas XA-26 prototype (AAC Ser. No. ''41-19504'') first flew on 10 July 1942 at Mines Field, El Segundo, with test pilot Benny Howard at the controls. Flight tests revealed excellent performance and handling, but problems with engine cooling led to cowling changes and elimination of the propeller spinners on production aircraft. Repeated collapses during testing led to strengthening of the nose landing gear.〔Mesko 1980, p. 5.〕 The A-26 was originally built in two different configurations. The ''A-26B'' had a gun nose, which originally could be equipped with a combination of armament including .50 caliber machine guns, 20mm or 37mm auto cannon, or even a 75mm pack howitzer. Normally the gun nose version housed six (or later eight) .50 caliber machine guns, officially termed the "all-purpose nose", later commonly known as the "six-gun nose" or "eight-gun nose". The ''A-26C''s "glass" nose, officially termed the "Bombardier nose", contained a Norden bombsight for medium altitude precision bombing. The A-26C nose section included two fixed M-2 guns, later replaced by underwing gun packs or internal guns in the wings.〔Borland, Hal. ("Plane of Many Faces." ) ''Popular Science,'' July 1945.〕 After about 1,570 production aircraft, three guns were installed in each wing, coinciding with the introduction of the "eight-gun nose" for A-26Bs, giving some configurations as many as 14 .50 in (12.7 mm) machine guns in a fixed forward mount. An A-26C nose section could be exchanged for an A-26B nose section, or vice versa, in a few man-hours, thus physically (and officially) changing the designation and operational role. The "flat-topped" canopy was changed in late 1944 after about 820 production aircraft, to a clamshell style with greatly improved visibility.〔Winchester 2004, p. 75.〕〔Thompson 2002〕 Alongside the pilot in an A-26B, a crew member typically served as navigator and gun loader for the pilot-operated nose guns. In an A-26C, that crew member served as navigator and bombardier, and relocated to the nose section for the bombing phase of an operation. A small number of A-26Cs were fitted with dual flight controls, some parts of which could be disabled in flight to allow limited access to the nose section. A tractor-style "jump seat" was located behind the "navigator's seat." In most missions, a third crew member in the rear gunner's compartment operated the remotely controlled dorsal and ventral gun turrets, with access to and from the cockpit possible via the bomb bay only when that was empty.〔Johnsen 1999〕 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「Douglas A-26 Invader」の詳細全文を読む スポンサード リンク
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