The Martin XB-48 was an early American jet bomber that reached the prototype stage, but didn’t enter production.
In 1944 the USAAF issued a request for designs for a high performance jet bomber, getting replies from North American, Convair, Boeing and Martin. Martin’s Model 223 was a six engine design. It had a narrow high mounted wing with a straight leading edge and tapered trailing edge. The six engines were carried in separate pods mounted close together under each wing. A strip of sheet metal connected the base of the pods, making them look like a single unit, but actually producing cooling tunnels in the gaps between the engines. The wings were too narrow to contain the main landing gear, so a new ‘bicycle’ system was developed. This had the main wheels carried fore and aft in the main fuselage, with two wheels in each position, and much smaller balance wheels on the outside of the engines.
The B-48 could carry a single 20,000lb bomb over a short distance, or 8,000lb of bombs over 2,500 miles. Power came from six Allison J35-A-5 turbojets. Martin produced two prototypes, the first of which made its maiden flight on 22 June 1947. It had a top speed of 495mph, but its overall performance wasn’t impressive enough to justify further production, so only the prototypes were ever built.
Engine: Six Allison J35-A-5 turbojets
Power: 3,750lb thrust each
Span: 108ft 4in
Length: 85ft 8in
Height: 26ft 6in
Empty Weight: 58,260lb
Gross Weight: 102,600lb
Maximum Speed: 495mph
Climb rate: 2,600ft/ min
Range: 2,500 miles with 8,000lb payload
Bomb load: 20,000lb