B 29 Superfortress

The major production version of the Superfortress was the B-29, 2513 of which were built. 1620 of them were built by Boeing at its Wichita, Kansas plant, 536 by Martin at its Omaha, Nebraska plant, and 357 by Bell at its plant in Marietta, Georgia.

The B-29 differed from the test models in having 16-foot 7-inch diameter fully-feathering four-bladed propellers. The engines were Wright R-3350-23, with a war emergency rating of 2300 hp. Only the very early Wichita-built models were delivered in olive drab and grey camouflage paint, with the remainder being delivered unpainted.

The first production B-29s began to roll off the production lines at Boeing-Wichita in September of 1943. The first B-29s appeared on the production lines at Bell-Atlanta (Marietta) in February of 1944. The first Martin-Omaha B-29 was delivered in mid-1944. The new Boeing plant at Renton built only the B-29A version.

The crew of the B-29 was typically eleven, comprising pilot, co-pilot, bombardier, navigator, flight engineer, radio operator, radar operator, central fire control gunner, left side gunner, right side gunner and tail gunner. The first six crewmen were housed in the forward pressurized cabin. The next four were housed in the rear pressurized cabin. The tail gunner was in a separate pressurized compartment in the tail. Later in the war, the crew size was occasionally increased to 13 with the addition of two radar/radio operators to man the radar and electronic countermeasures equipment.

Fuel was carried in fourteen outer-wing, eight inner-wing, and four bomb bay tanks, giving a maximum capacity of 8168 US gallons. An early modification added four tanks in the wing centre section, bringing total fuel capacity to 9438 US gallons.

The early models of the B-29 carried the Philco AN/APN-4 Loran (LOng RANge) constant-beam navigation aid. It was replaced by the more sophisticated RCA AN/APN-9 system later in World War II.

The B-29 carried an AN/APQ-13 radar bombing/navigational aid set. This set was developed jointly by the Bell Telephone Laboratories and the Massachusetts Institute of Technology Radiation Laboratory. It was manufactured by Western Electric, which was in those days the manufacturing arm of the Bell System. The radar antenna for this unit was housed inside a retractable 30-inch hemispherical radar dome located between the bomb bays and protruding below the fuselage a couple of feet when extended. Later in the war, the AN/APQ-7 Eagle radar unit was used. The Eagle antenna was mounted in a wing-shaped housing installed underneath the forward section of the fuselage. The unit was also devised by Bell Labs and MIT, and was manufactured by Western Electric.

There were numerous variations within the production blocks. Boeing-Wichita models reached block number -100 in increments of five, and Martin and Bell reaching -60 and -65, respectively.

Early combat experience indicated that the B-29 needed more protection against fighter attacks coming from the front. The forward dorsal turret armament was increased to four 0.50-inch machine guns on Boeing-Wichita production Block 40. Bell-Atlanta introduced this innovation on Block 10, and all Martin-built B-29s had four guns in the top turret from the beginning.

In the initial B-29 models, fuel was carried in fourteen outer-wing, eight inner-wing, and four bomb bay tanks, giving a maximum capacity of 8168 US gallons. An early modification added four tanks in the wing centre section, bringing total fuel capacity to 9438 US gallons. This extra fuel was first introduced on Block 25 aircraft from Boeing-Wichita and on Block 5 B-29s from Bell. Martin-built B-29s had these extra wing tanks from the beginning.

The R-3350-41 engine was introduced by Boeing on the Block 50 B-29. Both Martin and Bell followed suit on Block 20. The R-3350-41 had baffles and oil crossover pipes in an attempt to improve the cooling.

The trajectory of the shells fired from the 20-mm cannon in the tail was completely different from that of the bullets from the 0.50-inch machine guns, which made aiming difficult in combat conditions. Consequently, the 20-mm cannon was deleted from the tail position beginning with Boeing-Wichita production Block 55, Bell-Atlanta Block 25 and Martin-Omaha Block 25.

By the end of the production run, all three companies had begun to use the R-3350-57 engine.

Lingering doubts of about the efficacy of the remotely-controlled armament system resulted in the completion of one B-29-25-BW (42-2444) with manned turrets. This plane featured two manned power-operated dorsal turrets and two manned ventral "ball" turrets, each with two 0.50-inch machine guns. There was a single 0.50-inch gun in each of two beam positions, and two additional 0.50 guns in a blister on each side of the fuselage nose. The remotely-controlled armament system of the standard B-29 proved to be adequate, and this unique armament scheme was not pursued any further.

The last B-29 was delivered by Boeing-Wichita in October of 1945. The last B-29 was delivered by Bell-Atlanta in January of 1945, when it was replaced by the B-29B on the production line. The last B-29 was delivered by Martin-Omaha in September of 1945.

Specification of the Boeing B-29 Superfortress:
Power plant:
Four Wright R-3350-23 Duplex Cyclone eighteen-cylinder air-cooled radial engines each with two General Electric turbo superchargers, 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 3250 miles at 25,000 feet with 5000 pound bomb load. Practical operational radius was 1600-1800 miles. Maximum ferry range was 5600 miles, rising to 6000 miles with the extra fuel.
Weights:
74,500 pounds empty, normal loaded 120,000 pounds, maximum overload 135,000 pounds.
Dimensions:
Wingspan 141 feet 3 inches, length 99 feet 0 inches, height 27 feet 9 inches, wing area 1736 square feet.
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. Later, two more guns were provided for 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.

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