The Soviet-built copy of the B-29 was called the Tupolev Tu-4. Modifications led to the B-29D, upgraded to the B-50, and the RB-29 photoreconnaissance aircraft. The B-29 used the high-speed Boeing 117 airfoil, and its larger Fowler flaps added to the wing area as they increased lift.
The B-29 was also the world’s heaviest production plane because of increases in range, bomb load and defensive requirements. The tail gunner had a separate pressurized area that could only be entered or left at altitudes that did not require pressurization. Two crew areas, fore and aft, were pressurized and connected by a long tube over the bomb bays, allowing crew members to crawl between them. One of the most technologically advanced airplanes of World War II, the B-29 had many new features, including guns that could be fired by remote control. Boeing submitted the proposal for the B-29 long-range heavy bomber to the Army in 1940, before the United States entered World War II.
