B-26 Marauder - Design
Based on its design specifications alone, the B-26 offered the Air Corps significant capabilities. Its promised maximum speed of 322 mph topped its predecessors by a wide margin. The Douglas B-18, a twin-engine bomber delivered in 1937, topped out at 217 mph. With a bomb load rivaling most configurations of early B-17 variants and nearly twice that of light bombers, the Marauder offered significant offensive power. The Marauder’s multiple gun locations enabled it to strafe ground targets and defend itself from attacking fighters. The aircraft’s gun configuration changed multiple times, even during initial production, but all models at least included nose, dorsal, and tail firing positions. The Marauder’s dorsal turret, modified in early production to house twin .50 caliber guns, proved extremely successful and was later used in the B24. Martin had truly designed a powerful bomber that could fly like a fighter.
The general design scheme was that of a low-drag profile rotated. Years before this design had been advanced for the construction of a radical-type wing. The result traced out a symmetrically perfect fuselage and nacelle with very low drag. The inside diameter of the fuselage was sixty-seven inches, the same as the width at the point where the pilot can see the wing tips past the propellers.
To attain the requisite speed, a wing loading somewhat higher than had been considered normal in previous designs was used. A front bomb bay, almost identical to that of the B-17, was installed and an extra one was added to the rear to account for the highest maximum bomb capacity. Before the first bomber left final assembly the original armament was increased greatly and .50-calibers were installed in the tail and in a deck turret, which was power operated in azimuth and manually operated in elevation.
The design of Marauder combined quite traditional for that time general layout of the aircraft with the use of the most advanced technological solutions. The scheme of a free-carrying monoplane, all-metal construction, three-wheeled chassis with a nose wheel at that time was no longer a novelty. However, the high wing had an unusually small area for the aircraft of such a weight, which created a load on the wing of 223 kg / sq. M - more than any other aircraft that was then in service in the US.
This approach allowed to reduce aerodynamic resistance and raise the maximum speed of flight, although at the same time made it difficult to take off and land. Marauder consciously made the choice of "speed due to takeoff and landing characteristics", given that the landing speed was not specified in the task. The aerodynamics of the bomber also improved the choice of a round spindle-shaped fuselage round the section. For this it was necessary to pay with complex technology of manufacturing of panels of a fuselage: they all had a double curvature and were made by pressing.
In general, Martin Martin 179 introduced many technological innovations: widely used spot welding instead of labor-intensive riveting, used parts from plastics, introduced new ways of casting aluminum alloys. From the very beginning, the design was based on the requirements of mass production. The whole plane was broken up into three dozen main nodes, which in turn were assembled from 600 knots smaller. Many forgings, castings and stamped parts were used. Due to the large size of the aircraft, the dimensions of these parts were also very significant. However, the company was ready to produce them using powerful presses and advanced technology. According to the concept of the designers, the bomber could be operated in a wide range of climatic zones, which was taken into account in the choice of materials and design of the nodes.
It was the first turret of its kind installed on an American bomber. Boxes with ammunition (400 rounds) were located around the turret platform. The trunks could be raised about 70°. The turret itself rotated 360° and had a safety device to protect the keel. Subsequently, the same successful turret was introduced on the B-25 and A-20G. It was supposed to have another 12.7-mm machine gun in the rear of the fuselage, shooting through the hatch in the floor behind the rear bomb bay. The company's calculations showed that the empty and maximum take-off weight will be respectively 8732 kg and 12,077 kg, and the maximum speed - 520 km / h. The working ceiling was estimated at 8060 m, the range with the bomb load of 1360 kg - at 2900 km. In two bombshek, in theory, it was possible to load 2,630 kg of bombs.
An assessment of pre-war expectation versus wartime reality for the Marauder, however, is ambiguous. First, the Marauder’s ultimate role, almost paradoxically, more closely resembled pre-war thinking than did the roles applied to most other aircraft types. The B-26 entered the war without a clearly defined role, but the war radically altered the roles of all aircraft. Second, B-26 units, like all Airmen of WWII, adapted throughout the war. Whereas most Airmen deviated from relatively rigid pre-war doctrines, B-26 crews began from a comparatively clean slate requiring trial and error even in initial operations.
The B-26 was not a strategic bomber. The Marauder’s limited range precluded it from significant participation in the strategic bombing offensive. On the opposite extreme, the AAF did not use the B-26 primarily at the battle line in direct support of ground forces. That role fell largely to fighter bombers. Marauder groups, including the 397th, did accomplish direct support missions, though such missions were exceptional. The B-26 was also not a pure attack aviation platform. This point, however, requires clarification. Definitions of attack aviation differed and evolved both before and during the war. Put simply, Marauder units provided airpower through bombardment against any necessary target within their range.
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