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Boeing XB-55

1947 COLD WAR X-PLANE

The history of the Boeing XB-55

The United States Air Force (USAF) did not believe in the reliability of early turbojets and promised their performance. The Boeing B-47 "Stratojet" swept-wing strategic jet bomber was selected by the USAF to meet early specifications and was a product of the period - it was ultimately a success, with more than 2,000 built and flown by the USAF Examples of this type.

Late 1970s.

In October of that year, even before the B-47 prototype took off in 1947, US Air Force authorities made a new request for an insurance-focused strategic bombing platform that would rely on more traditional propulsion power. The usual participants reacted, and the batch also included Boeing, the template of which was chosen for further development under the designation "XB-55" (company type 474).

Boeing engineers identified a form that was no different from their B-47 proposal, except that it used an Allison T40-A-2 turboprop instead of a turbojet. These systems would be mounted under the wings in the usual way (the wing main aircraft has a smaller downsweep compared to the B-47) and drive three-bladed counter-rotating propeller units. Four engines will power the large bomber, producing up to 5,600 horsepower. Estimated performance includes a top speed of 490 mph (going at about 450 mph), a range of up to 5,000 miles, and a ceiling of 42,000 feet.

By comparison, the B-47 (B-47E) has a top speed of 607 mph, a cruising speed of 557 mph, a flight altitude of 4,650 miles, and an altitude of 33,100 feet.

The XB-55 has a crew of 10 and has an overall fuselage length of 119 feet, a wingspan of 135 feet, and a height of 33.7 feet. The reported maximum takeoff weight (MTOW) is 168,000 pounds. Like the B-47, the XB-55 had a "bicycle" landing gear arrangement, keeping the main legs under the fuselage and using outriggers to support the wings.

Standard defensive armament includes a 10 x 20mm gun, while the store's bomb load reaches 24,000 lbs. The B-47 was defended by 2 x 20mm guns and carried approximately 25,000 pounds of ammunition.

In many ways, the XB-55 is an insurance policy against the B-47 - it's more traditional in design and has the qualities of a WWII-influenced bomber, but the USAF can at least understand that they don't get what they have All hope was on the success (or failure) of the then unreliable, underperforming and thirsty turbojets.

Finally, the expected delay in the Allison engine has drawn attention to a pure turbojet form under the "XB-52" program - a design that promises a significant performance boost from the upcoming Pratt & Whitney J57 turbojet Data - Engine. Coupled with waning interest in the XB-55 in the USAF (by which time the B-47 was successfully operating), the contract for the XB-55 program was terminated in 1949.

The USAF realized once again that a fleet of fast bombers and turboprops was not enough.

The XB0-55 effort had a shorter lifespan than the "Type 479", which studied the use of 6 x Westinghouse J40 turbojets along with modified wing elements, and then applied that data to the upcoming Boeing B- 52 The Stratofortress Strategic Heavyweight Bomber Program. The remainder of the XB-55 funds were used to develop Boeing's supersonic strategic bomber designated the "XB-59" (Type 701).

As no working prototype of the XB-55 has been completed, the specifications given in this article and on this page are only estimates based on technical data.