The B-29A was the version of the Superfortress built by Boeing at the Navy-owned Renton plant. The B-29A was essentially the same as the B-29, differing from the B-29 primarily in the wing center structure.
The B-29 had employed a two-piece wing center section that was bolted together at the center line and which was installed as a single unit passing entirely through the fuselage and supporting the engine nacelles. The B-29A used a very short stub center section that did not project beyond the fuselage sides, being only 47.75 inches wide on either side of the center line or almost eight feet in total. Each pair of engine nacelles was fitted to a separate short section of wing. The outer wing panels were attached at the same point on B-29s and B-29As alike.
These wing changes were internal only, and there were no external differences visible in the wing root area, except for the overwing panelling on the fuselage Contrary to what has been posted elsewhere, this change did not give the B-29A an additional foot of wingspan as compared to the B-29.
The B-29A was powered by four R-3350-57 engines. 1119 B-29As were built, with block numbers reaching -75. The 20-mm cannon was removed from the tail turret beginning with production block 20, and a pair of 0.50-inch guns were added to the top forward turret to provide additional protection against fighter attacks coming from the front.
Revised engine nacelles were developed and tested and were to be used on late-model B-29As. These engine nacelles had the oil coolers and intercoolers moved further aft, which gave them a "chinless" appearance. Because of this chinless appearance, these nacelles became known by the nickname *Andy Gump*, who was a famous cartoon character of the period.
Some early B-29As were fitted with pneumatically-operated bomb-bay doors which could be snapped shut in less than a second. The normal hydraulic doors took seven seconds to close. By early 1945, all B-29s were being manufactured with pneumatic doors as a standard fit.
The B-29 had always been somewhat underpowered for its weight, and in search of more power, one B-29A (42-93845) was handed over to Pratt & Whitney for conversion as a testbed for the four-row 28-cylinder Pratt & Whitney R-4360 air-cooled radial engine. This aircraft was later redesignated XB-44, and was readily recognizable by the new engine installation, with the oil cooler intake pulled further back on the lower part of the nacelle. The aircraft had initially ordered into production as the B-29D, but all contracts were cancelled at the end of the war. However, the B-29D project was later reinstated as B-50A.
42-93824/93843 Boeing B-29A-1-BN Superfortress 42-93844/93873 Boeing B-29A-5-BN Superfortress 93845 converted to XB-44, progenitor of B-50. 42-93874/93923 Boeing B-29A-10-BN Superfortress 42-93874/93923 Boeing B-29A-10-BN Superfortress 42-93924/93973 Boeing B-29A-15-BN Superfortress 42-93974/94023 Boeing B-29A-20-BN Superfortress 42-94024/94073 Boeing B-29A-25-BN Superfortress 42-94074/94123 Boeing B-29A-30-BN Superfortress 44-61510/61609 Boeing B-29A-35-BN Superfortress 44-61610/61709 Boeing B-29A-40-BN Superfortress 44-61710/61809 Boeing B-29A-45-BN Superfortress 44-61810/61909 Boeing B-29A-50-BN Superfortress 44-61910/62009 Boeing B-29A-55-BN Superfortress 44-62010/62109 Boeing B-29A-60-BN Superfortress 44-62110/62209 Boeing B-29A-65-BN Superfortress 44-62210/62328 Boeing B-29A-70-BN Superfortress
Engines: Four Wright R-3350-57 Duplex Cyclone eighteen-cylinder air-cooled radial engines each with two General Electric turbosuperchargers, delivering 2200 hp for takeoff and having a war emergency rating of 2300 hp at 25,000 feet. Performance: Maximum speed 357 mph at 30,000 feet, 306 mph at sea level. Maximum continuous cruising speed 342 mph at 30,000 feet. Economical cruising speed 220 mph at 25,000 feet. Initial climb rate 900 feet per minute at combat weight. An altitude of 20,000 feet could be attained in 38 minutes. Service ceiling 33,600 feet. Maximum range was 4000 miles at 25,000 feet with 5000 pound bomb load. Practical operational radius was 1800 miles. Maximum ferry range was 6000 miles. Weights: 71,360 pounds empty, Normal loaded 120,000 pounds, maximum overload 135,000 pounds with 12,000 pound bombload. Dimensions: wingspan 141 feet 2 3/4 inches, length 99 feet 0 inches, height 27 feet 9 inches, wing area 1738 square feet. Fuel: 8288 US gallons after installation of semipermanent bomb bay tanks. Armament: Twelve 0.50-inch machine guns in four remotely-controlled turrets (two above and two below the fuselage) and in the tail, each with 1000 rounds of ammunition. In addition, early production blocks had a single rearward-firing 20-mm M2 Type B cannon with 100 rounds in the tail position. The 20-mm cannon was deleted on production block 20 and two more 0.50-inch guns were added to the forward top turret.. Maximum internal short-range, low-altitude bomb load was 20,000 pounds. A load of 5000 pounds of bombs could be carried over a 1600-mile radius at high altitude. A load of 12,000 pounds of bombs could be carried over a 1600-mile radius at medium altitude.