During World War II, three models of the Superfortress were manufactured: the B-29, B-20A and the B-29B.
After the war, B-29s were adapted for several functions, including in-flight refueling as the KB-29, anti-submarine patrol, the RB-29 reconnaissance version, WB-29 weather reconnaissance, and rescue duty.
Two tanker versions were developed and produced: KB-29M and KB-29P. The B-29 played an important role in developing the effective use of aerial refueling during the late 1940s. The first aircraft produced for aerial refueling was the KB-29M tanker which used a flexible hose approach.
A more refined system was used in the KB-29P, involving a rigid flying boom system. The boom was mounted on the aftmost end of the KB-29P, and had two small wings. This approach would later be used in other Air Force tankers, including the KB-50, KC-97, KC-135 and KC-10.
The photo reconnaissance version of the B-29 was originally designated the F-13 Superfortress. In 1944 an F-13 became the first U.S. plane to fly over Tokyo since April 1942.
A total of 118 B-29 aircraft were reconfigured for photo work. In 1948, the F-13s were redesignated the RB-29 or the RB-29A.
The WB-29s were production aircraft modified to perform weather monitoring missions. An observation position was fitted above the central fuselage section. They conducted standard data-gathering flights, including from the England out over the Atlantic Ocean, but also used for accumulating hurricane weather data.
As the Air Force's largest aircraft in 1950, the WB-29 became the first aircraft to be designated with a "W" for weather service. The 53rd Weather Reconnaissance Squadron scored many "firsts" with the Superfortress. For example, in 1946 it was the first to fly into the top of a hurricane, at 22,000 feet (with the tops of clouds at 36,000 feet).
The TB-29 was a trainer version of B-29 used to train cresw for bombing missions. Other TB-29s were used to tow targets.
During World War II, the 509th Composite Group included 15 B-29s with special "Silverplate" modifications, and 1,800 men. The Silverplate B-29s had modifications necessary to deliver atomic weapons, which included an extensively modified bomb bay with pneumatic doors, special propellors, modified engines and the deletion of protective armor and gun turrets.
The XB-39 Superfortress was intended to prove that the B-29 could successfully operate if the first choice of engine, the air-cooled Wright R-3350 radial engine, ran into development or production difficulties. The XB-39 would be fitted with Allison V-3420-17 liquid-cooled W24 inline engines.
The project test bed was YB-29, S/N 41-36954; it was was transferred in November of 1943 to the Fisher Body Aircraft Development Section of General Motors to be fitted with the Allison engines.
The first flight of the B-39 was made on December 9, 1944 at Cleveland, Ohio. The initial flight tests of the B-39 were impressive. However, the B-29s in service were working at a level that made the XB-39 not worthwhile. Consequently, the B-39 project was cancelled and no other types were built.
Pratt and Whitney was provided B-29A S/N 42-93845 for testing of more powerful R-4360 radial engines. This aircraft was known as the XB-44, and later as the B-29D.
To secure funding for the new aircraft, and due to the aircraft's large number of modifications from the B-29, the designation was later changed from the B-29D to the B-50.
A later variant of the B-29, the B-50 made it maiden flight in 1947, originally named the B-29D. Essentially an improved version of the B-29, this aircraft's large number of modifications caused its redesignation as the B-50.
The B-50 was configured with more powerful Pratt & Whitney radial engines than the B-29, a stronger structure, a taller fin, and other improvements.
The Boeing B-54 was a strategic bomber designed by Boeing for use by the United States Air Force. Derived from the YB-50C Superfortress, construction of the prototype was cancelled before completion, and the aircraft was never flown.
After the war Boeing developed the Model 367, a military transport airplane based on the B-29 Superfortress bomber. Its civilian counterpart was the Model 377 Stratocruiser.
The C-97 Stratofreighter had a double-lobe fuselage consisting of two intersecting circular sections, so that the 74-foot-long upper deck had a larger diameter.
The Boeing 377, also called the Stratocruiser, was a large long-range airliner built after World War II. It was developed from the C-97 Stratofreighter.
The Tupolev Tu-4 is a reversed-engineered variant of the Boeing B-29. Using B-29s which made emergency landings in the Soviet territory, Tupolev engineers designed and built a clone of the B-29, with its first flight in May of 1947.
A total of 847 Tu-4s were reported built when production ended in 1952.
Tupolev Tu-4 on display at the Monino Museum
More about the B-29 Superfortress