Boeing B-29 Superfortress
|BOMBER||Virtual Aircraft Museum / USA / Boeing|
The outbreak of war in Europe in 1939 made it essential that USAAC planners should at least talk about long-range bomber projects, and the initial identification of such was VHB (very heavy bomber). When it seemed likely that such an aircraft might have to be deployed over the vast reaches of the Pacific Ocean the identification VLR (very long-range) seemed more apt, and it was the VLR project which General Henry H. ('Hap') Arnold, head of the USAAC, got under way at the beginning of 1940.
Requests for proposals were sent to five US aircraft manufacturers on 29 January 1940: in due course design studies were submitted by Boeing, Consolidated, Douglas and Lockheed, these being allocated the respective designations XB-29, XB-32, XB-31 and XB-30. Douglas and Lockheed subsequently withdrew from the competition, and on 6 September 1940 contracts were awarded to Boeing and Consolidated (later Convair) for the construction and development of two (later three) prototypes of their respective designs. Convair's XB-32 Dominator was the first to fly, on 7 September 1942, but extensive development delayed its entry into service.
Boeing, because of the company's foresight, was much further along the design road in 1940, and being able to convince the USAAC that it would have production aircraft available within two or three years, had received orders for more than 1,500 before a prototype was flown. The reason for the advanced design state of Boeing's proposal was due to the fact that as early as 1938 the company had offered to the USAAC its ideas for an improved B-17, with a pressurised cabin to make high-altitude operations less demanding on the crew. While there was then no requirement for such an aircraft, the US Army encouraged Boeing to keep the design updated to meet the changing conditions of war. This was reflected by designs identified as Models 316, 322, 333, 334 and 341. The design for the XB-29 was a development of the Model 341, designated Model 345, and the first of the prototypes made its maiden flight on 21 September 1942.
The USAAC's specification had called for a speed of 644km/h, so the XB-29 had a high aspect ratio cantilever monoplane wing mid-set on the circular-section fuselage. Because such a wing would entail a high landing speed, the wide-span trailing-edge flaps were of the Fowler type which effectively increased wing area by almost 20%, thus allowing a landing to be made at lower speed. Electrically retractable tricycle landing gear was provided and, as originally proposed by Boeing, pressurised accommodation was included for the flight crew. In addition, a second pressurised compartment just aft of the wing gave accommodation to crew members who, in the third XB-29 and production aircraft, sighted defensive gun turrets from adjacent blister windows. The crew and aft compartments were connected by a crawl-tunnel which passed over the fore and aft bomb bays. The tail gunner was accommodated in a pressurised compartment, but this was isolated from the other crew positions. The powerplant consisted of four Wright R-3350 Cyclone twin-row radial engines, each with two General Electric turbochargers mounted one in each side of the engine nacelle.
Prototype production was followed by 14 YB-29 service test aircraft, the first of these flying on 26 June 1943. Deliveries of YB-29s began almost immediately to the 58th Very Heavy Bombardment Wing (VHBW), a unit which had been established on 1 June in advance of the first flight. B-29 production was the most diverse aircraft manufacturing project undertaken in the USA during World War II, with literally thousands of sub-contractors supplying components or assemblies to the four main production plants: Boeing at Renton and Wichita; Bell at Marietta, Georgia; and Martin at Omaha, Nebraska.
B-29 production totalled 1,644 from Boeing's Wichita plant, with 668 built by Bell and 536 by Martin. The Renton plant produced only the B-29A variant, with slightly increased span and changes in fuel capacity and armament: production continued until May 1946 and totalled 1,122 aircraft.
The designation B-29B related to 311 of the aircraft built by Bell. These were reduced in weight by removal of all defensive armament except for the tail guns, which were then unmanned, being aimed and fired automatically by an AN/APG-15B radar fire-control system. The production total of nearly 4,000 B-29s of all versions must be regarded as very large, having regard to their size and cost, and it is not surprising that they saw a wide variety of employment in the post-war years, operating under several designations. A number of B-29s were used operationally during the Korean War.