These prototype B-52s were given the designations XB-52 and YB-52… X for ‘experimental’ and Y being the designation for ‘prototype.’
After it became operational in 1955, the B-52 remained the main long-range heavy bomber of the US Air Force during the Cold War, and it continues to be an important part of the USAF bomber force today.
As explained by Scott Lowther in his book Boeing B-47 Stratojet & B-52 Stratofortress Origins and Evolution, the winning design for the XB-52, Model 464-49, transitioned to Model 464-67. While largely the same, there were some notable differences, most obviously the extension of the forward Fuselage. Where 464-49 had the rear of the cockpit canopy behind the leading edge of the wing roots, 464-67 put the cockpit well ahead of the wing. The relatively vast expanse of spoilers on the wings were scaled down and the engine nacelles were reshaped. With those changes and an Air Force ‘letter of intent’ for B-52 tooling in March 1951, Boeing was ready to begin constructing two Model 464-67s.
These prototype B-52s were given the designations XB-52 and YB-52… X for ‘experimental’ and Y being the designation for ‘prototype.’ Typically an `experimental’ aircraft is built before a ‘prototype’, but in this case while the XB-52 (serial number 49- 230) rolled out on Nov. 29, 1951, and the YB-52 (serial number 49-231) followed on Mar. 15, 1952, the YB-52 flew first on Apr. 15, 1952. This was due to the XB-52 suffering damage during pneumatic system pressurization testing which required extensive repairs.
The XB-52 followed the prototype into the air on Oct. 2, 1952. The first flight of the YB-52 lasted two hours and was powered by prototype YJ57-P-3 engines. Despite the difference in designations, the XB-52 and the YB-52 were essentially identical.
The prototype B-52s were largely similar to the production aircraft in appearance. An immediately distinguishing feature of both aircraft, though, was the cockpit. A tandem fighter-style canopy somewhat similar to that used on the B-47 was employed; it was low-drag and gave the pilot excellent visibility.
The prototypes pioneered the landing gear layout that the rest of the B-52 fleet would employ. Somewhat similar at first glance to the bicycle arrangement used by the B-47, the gear used by the B-52 was quite different. Four separate dual-wheel bogies were stored within the B-52 fuselage, but instead of deploying straight down they deployed out to the sides, twisting around so that the bogies stored fore-and-aft ended up side-by-side. This gave the B-52 not a bicycle arrangement, but a quadricycle. The B-52 would comfortably sit level on its main landing gear and not tip to one side or the other. It still employed smaller outrigger gear near the wingtips, but this was to keep the wingtips from striking the ground during heavily laden takeoffs or bumpy landings.
Additionally, the forward bogies could rotate up to 20° side to side, allowing the B-52 to do something unique: land while ‘crabbing’ into the wind, the fuselage of the aircraft pointed well off the axis of the groundpath of the flight. This would permit safe landings in high winds.
The prototypes had flapperons, ailerons and spoilers on the main wings. The ailerons were relatively small and located far from the wingtip; in fact, just outboard of the inboard engine pylon. A wingtip location for the ailerons would have given them more authority, but that would have put them in a much thinner section of the wing, a section much given to flexing. The inboard location was sufficient for the manoeuvring that the bomber was expected to perform.
In any event, the spoilers were to take care of the bulk of the control needs of the aircraft, and the ailerons would eventually find themselves redundant. Unlike the production aircraft that followed, the prototypes did not have the capability for inflight refuelling. Neither did they, initially, have the external fuel tanks that generally graced the outer wings of production model B-52s, but such tanks were eventually added later in the testing phase.
The horizontal stabilizers were all-moving, but this was meant for trim stabilization. Actual control was via slim elevators along the trailing edge. The elevators had, through the B-52F, trim tabs. An important but rarely noted feature not only of the prototype B-52s but of all B-52s that followed was the folding vertical fin. The fin was, at least until the G-model, a vast structure; too tall by far to allow the B-52 to fit within standard hangars. So it could fold over 90-degrees, greatly reducing the effective height of the aircraft. Unlike naval aircraft with wings that fold to fit in the limited space on board aircraft carriers, the fielding fin is not a self-contained system — an external crane is needed to lay it over and raise it back up again.
The prototypes were essentially hand-made at the Boeing Seattle factory. Production methods were not used as the jigs were not finalized; the equipment and instruments employed were also often not what would become standard. Neither prototype was fitted with defensive weapons; the tail turrets were represented by static fairings, with the painted-on lines.
The YB-52 was donated to the US Air Force Museum on Jan. 27, 1958, having flown for 783 hours. It was on display for a time but due to a ‘beautification’ scheme orchestrated by First Lady Lady Bird Johnson, both the XB-52 and YB-52 were scrapped sometime in the 1960s. Exactly how the official museum of the United States Air Force was ‘beautified’ by converting one of the most beautiful aircraft ever built into razor blades and soda cans is not adequately explained in the available literature.
Boeing B-47 Stratojet & B-52 Stratofortress Origins and Evolution is published by Mortons Books and is available to order here.
Photo credit: U.S. Air Force