Boeing B-29 Super Fortress Family
I had a thought experiment, what if the USAF never redesignated the B-39, B-44, B-50 and B-54, and kept its original designation of B-29, how big would the family be.
XB-29: prototype with Wright R-3350-13 engines
YB-29: preproduction version with Wright R-3350-21 engines.
B-29: original production version
B-29A: improved version
B-29B: modified version used for low-level raids, designed with the intent of firebombing Japan. All defensive armament was removed except for that in the tail turret.
B-29C: modified B-29A with improved Wright R-3350 engines
XB-44 (B-29D): a B-29A-5-BN modified by Pratt & Whitney to use the four-row, 28-cylinder Pratt & Whitney R-4360 Wasp Major radial engine. This was originally going to be the B-29D but came after WWII. With orders for several of existing aircraft orders being cancelled, the USAF redesigned it B-50A as a ploy since new design aircraft weren't being cancelled.
XB-29E: a B-29-45-BW with a modified fire-control systems.
B-29F: cold-weather version for operation in Alaska.
XB-29G: testbed for jet engines.
XB-29H: testbed for armament configurations
B-29I: letter not used.
RB-29J: the F-13, a reconnaissance version of the B-29, being redesignated FB-29J, later redesignated again to YB-29J, then RB-29J. They were modified with the Wright R-3350-CA-2 fuel injected engines.
XB-39 (B-29K): Single YB-29 modified by General Motors to use water-cooled Allison V-3420-17 Vee type engines, no improvement was gained.
B-50A (B-29L): the production version of the B-44, originally B-29D.
B-50B (B-29M): Improved version of the B-50A
B-50C/B-54 (B-29N): modified to use the Pratt & Whitney R-4360-51 Variable Discharge Turbine (VDT) engines, the fuselage was lengthened by over 10 feet (3.0 m) and the wingspan was extended by 20 feet (6.1 m), which required the installation of outrigger landing gear in the first and fourth engine nacelles.
B-50D (B-29O): Improved version of the B-50B, final bomber version.
RB-50E (RB-29P): RB-50B modified for specialist photographic reconnaissance
RB-50F (RB-29Q): modified for reconnaissance, fitted with SHORAN navigation radar.
RB-50G (RB-29R): RB-50B modified for electronic reconnaissance. Fitted with Shoran for navigation, and six electronic stations.
TB-50H (TB-29S): crew trainer version for B-47 squadrons.
KB-50J (KB-29T): air-to-air refueling tankers with improved performance from two extra General Electric J47 turbojets under the outer wings.
KB-50K (KB-29U): TB-50H modified to be Tankers.
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