Key Points and Summary – The Martin XB-48 was an experimental American jet bomber developed immediately after World War II.
-It represents a design “stuck between two worlds,” mating six new jet engines to a conservative, WWII-era straight-wing airframe.
-While a competitor, the Boeing B-47 Stratojet, used a revolutionary swept-wing design for higher speeds, the XB-48’s obsolete configuration made it slower and less efficient.
-Deemed a failure almost immediately, the underperforming XB-48 lost the Air Force competition. Only two prototypes were ever built, dooming the bizarre bomber to obscurity.
XB-47 vs. B-47: We Have A Winner
The Martin XB-48 was an experimental medium bomber developed in the mid-1940s for the United States Air Force.
The unusual bomber was a unique platform that represented the transition from aircraft typical of the Second World War and the new technology of the jet age. Designed by the Glenn L. Martin Company, an aerospace firm, for the U.S. Army air Forces, the precursor to today’s U.S. Air Force, the XB-48 is a good example of how quickly aerospace technology progressed in the years following the war, and an exemplar of how some aircraft could not keep up with competing aircraft, both literally and figuratively.
The Competition
The XB-48 was the product of a competition that included the North American XB-45, Convair XB-46, and the Boeing XB-47, which were initial explorations into mating jet engine technology with medium bombers.
At the time of the competition, jet engines were still in their infancy, and aerospace firms sought to minimize risk wherever possible.
Martin’s XB-48 was, in essence, a Second World War-era airframe, though with jet engines. Like many bombers of the wartime era, the XB-48 mounted a straight wing, to which six General Electric J35 turbojet engines were mounted in nacelles below the wings. In addition to a pressurized cockpit, tricycle landing gear, and a conventional tail arrangement, the jet was also outfitted with additional bicycle landing gear on the wings for improved handling during landing. The XB-48 first flew in 1947.
A Glenn L. Martin press release from 1947 explained that the “six-jet Martin XB-48, newest Army Air Forces high speed jet bomber, made its initial flight Sunday (22 June 1947) from the Glenn L. Martin Company airport in Baltimore to the Patuxent River (Maryland) Naval Air Station, remaining aloft 37 minutes. Powered by six General Electric J-35 gas turbine engines housed three in each wing, the Martin XB-48 has a speed of over 480 miles per hour and carries a bomb load of more than 10 tons.”
The Martin press release also added that the XB-48 used a “new type “bicycle” landing gear, because of the difficulty of retracting heavy gears into fragile wings required for high speeds. Two pairs of main wheels are located tandem-style under the fuselage, and two smaller “outrigger” wheels farther out under the wing, to give stability during ground operations. The large main gear folds into the fuselage, and the smaller wheels retract into the wings.”
It was an incredibly short-lived aircraft, and the Martin firm built only two prototypes before their XB-48 lost to what would become the B-47 Stratojet, a vastly superior platform in every regard that would be the main United States Air Force bomber for much of the 1950s and 1960s.
What Made the B-47 Special
The XB-48 was, in essence, caught between the past and the future. Though the increasingly high speeds afforded by jet engine technology called for a more aerodynamically-efficient swept-wing design, the XB-48 retained the straight wing of its Second World War predecessors. Despite sporting six jet engines, these engines were underpowered and consumed large amounts of fuel.
The B-47, in contrast, was revolutionary. That jet’s design featured swept wings, affording it greater top speeds and better fuel efficiency and range. The B-47’s podded engines were easier for mechanics to work on during maintenance and repair, and ran cooler. The B-47’s fuselage was also more streamlined, a crucial component of efficient flight.
The XB-48 is one of the prototypical examples of an airplane stuck between two ages: piston-powered propeller aircraft and the jet age. While it did feature some novelties, including bicycle landing gear and multiple jet engines, the XB-48’s overall design conservatism ultimately hampered the bomber’s performance, dooming the project to remain prototyped only.
The B-47 stands in striking contrast, a highly aerodynamic design that virtually all bombers and many fighter aircraft would follow in the future — and indeed, still do today. Thanks to that bold innovation philosophy, the B-47 would enjoy success as an important part of the American bomber fleet during the early years of the Cold War, while the XB-48 would fall into relative obscurity.
About the Author: Caleb Larson
Caleb Larson is an American multiformat journalist based in Berlin, Germany. His work covers the intersection of conflict and society, focusing on American foreign policy and European security. He has reported from Germany, Russia, and the United States. Most recently, he covered the war in Ukraine, reporting extensively on the war’s shifting battle lines from Donbas and writing on the war’s civilian and humanitarian toll. Previously, he worked as a Defense Reporter for POLITICO Europe. You can follow his latest work on X.
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