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Boeing B-54 (Ultrafortress)

Four-Engine, High-Altitude, Long-Range Heavy Bomber Proposal [ 1947 ]

Born from the YB-50C bomber prototype, the Boeing B-54 program saw only one incomplete prototype and a completed mockup before cancellation.

Authored By: Staff Writer | Last Edited: 05/09/2019 | Content ©www.MilitaryFactory.com | The following text is exclusive to this site.

Outstanding issues inherent in the original Boeing B-29 "Superfortress" strategic bomber design of World War 2 (1939-1945) prompted work on a more refined form and this became the "B-50" offering of 1948. Three-hundred seventy examples of the type were built and these saw service into 1965. Similar in form and function to the B-29 before it, the B-50 was essentially an all-new aircraft as it was given more powerful radial piston engines, a reinforced airframe, larger tail fin, and a slew of other benefits.

Even with these changes in place, there still remained carry-over issues with production B-50A bombers that pushed through an even more improved form - the YB-50C. A single B-50A production model was set aside and modified by way of new R-4369 "Variable Discharge Turbine" (VDT) radial piston engines, a 20-foot-longer wingspan, and a 10-foot-longer fuselage. Because of the increased overall dimensions of the aircraft, further reinforcement of the airframe was required and the added span to the wings also forced outrigger landing gear legs to be installed to support the weight of the wings while ground-running. The aircraft promised better operational ranges while operating at a higher altitude and carrying a larger war load.

The YB-50C project soon took on a development road all its own - apart from that of the B-50 series - that it was seen fit to redesignate the new aircraft as the "B-54". A mockup was completed during 1948 for review.

Despite the progress on the program, it coon became clear that jet-powered bomber forms would become the future of the USAF strategic bombing needs leaving the B-54 without a role to fill. This led to the termination of the B-54 program during1949 and no flyable examples were completed (constructed had begun on a prototype).

The USAF originally intended a first-order of 21 bomber forms in the "B-54A" guise and a further 52 would follow as the "RB-54A" - these outfitted with special reconnaissance equipment instead of a bomb-carrying capability.

As finalized, the B-54 design was to feature crew spaces for ten operators. Dimensions included a length of 34 meters, a wingspan of 49 meters, and a height of 10 meters. Gross weight was 104,326 kilograms. The engines of choice became 4 x Pratt & Whitney R-4360-51 series radial piston engines of 4,500 horsepower each. Estimated performance specs included a maximum speed of 430 miles per hour, a cruise speed of 305 miles per hour, a range out to 9,000 miles, and a service ceiling of 40,000 feet.

In terms of armament, there would have been 14 x 0.50 caliber heavy machine guns fitted to several remote-controlled turrets about the aircraft for local defense against interceptors. The conventional bomb load was rated at 36,000lb.©MilitaryFactory.com
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Service Year

United States national flag graphic
United States

Development Ended.


National flag of the United States United States (cancelled)
(OPERATORS list includes past, present, and future operators when applicable)
Ground Attack (Bombing, Strafing)
Ability to conduct aerial bombing of ground targets by way of (but not limited to) guns, bombs, missiles, rockets, and the like.
X-Plane (Developmental, Prototype, Technology Demonstrator)
Aircraft developed for the role of prototyping, technology demonstration, or research / data collection.

111.5 ft
(34.00 m)
160.8 ft
(49.00 m)
32.6 ft
(9.95 m)
Empty Wgt
168,654 lb
(76,500 kg)
229,997 lb
(104,325 kg)
Wgt Diff
+61,344 lb
(+27,825 kg)
(Showcased structural values pertain to the base Boeing B-54 (Ultrafortress) production variant)
Installed: 4 x Pratt & Whitney R-4360-51 radial piston engines (w/ variable discharge turbines) developing 4,500 horsepower each and driving four-bladed propeller units.
Max Speed
432 mph
(695 kph | 375 kts)
40,026 ft
(12,200 m | 8 mi)
9,010 mi
(14,500 km | 26,854 nm)

♦ MACH Regime (Sonic)
RANGES (MPH) Subsonic: <614mph | Transonic: 614-921 | Supersonic: 921-3836 | Hypersonic: 3836-7673 | Hi-Hypersonic: 7673-19180 | Reentry: >19030

(Showcased performance specifications pertain to the base Boeing B-54 (Ultrafortress) production variant. Performance specifications showcased above are subject to environmental factors as well as aircraft configuration. Estimates are made when Real Data not available. Compare this aircraft entry against any other in our database or View aircraft by powerplant type)
14 x 0.50 caliber Browning M2 heavy machine guns in remote-controlled turrets (assumed dorsal, ventral, and tail turret locations).

Up to 36,000lb of internally-held stores (conventional drop bombs).

Supported Types

Graphical image of an aircraft medium machine gun
Graphical image of an aircraft heavy machine gun
Graphical image of an aircraft conventional drop bomb munition

(Not all ordnance types may be represented in the showcase above)
Hardpoint Mountings: 0

B-54 - Base Series Designation; based on the YB-50C prototype; incomplete prototype and completed mockup.
B-54A - Proposed production bomber designation
RB-54A - Proposed production reconnaissance variant

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Image of the Boeing B-54 (Ultrafortress)
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