Look quickly and you might call it a Sabre. Look again and the differences pile up: a fatter fuselage, twin-wheel landing gear, cannon in the nose, and — strangest of all — no air intake at the front. This was the North American YF-93, a fighter built to fly halfway across a continent and still win a dogfight at the far end.

It should have been a star. The U.S. Air Force ordered 118 of them. Instead, the production contract was killed before the prototype had even flown, and only two YF-93As were ever built. Both ended their days not as fighters but as flying laboratories.

The YF-93 is the story of a very good aircraft overtaken by a very fast bomber.

A Sabre stretched for range

The problem the YF-93 was built to solve was as old as strategic bombing itself: bombers deep in enemy airspace need fighter escort, and early jets simply could not carry enough fuel to get there and back. In 1946 the USAAF asked for a “penetration fighter” with a combat radius of at least 900 miles that could still out-fight anything it met.

North American’s answer, project NA-157, kept the Sabre’s swept wing and tail but changed almost everything else. A bigger Pratt & Whitney J48 engine replaced the Sabre’s J47, the fuselage grew wider and longer to swallow 1,580 gallons of fuel, and the landing gear was beefed up with twin main wheels. A search radar was planned for the nose — which is why the air intakes migrated to the sides of the fuselage.

The first prototype took the boldest step of all: instead of conventional scoops, it wore flush NACA-designed intakes let into the fuselage sides, in the hope of cutting drag. The second aircraft was fitted with ordinary scoops, setting up a neat head-to-head experiment.

Killed by the B-47

In June 1948 the Air Force backed its favourite with an order for 118 production aircraft, and the design was redesignated YF-93A. Then, in February 1949, the whole thing collapsed. The budget for 1949 was slashed, priority went to interceptors and bombers — and the new Boeing B-47 Stratojet was so fast that planners decided it would not need a fighter escort at all.

The two prototypes were finished anyway, purely to compete in a fly-off against the Lockheed XF-90 and McDonnell XF-88. On 15 August 1950 the board declared the XF-88 the winner — but it was a victory over an already-doomed idea.

A second life for science

Both YF-93As were handed to NACA’s Ames Laboratory at Moffett Field, where the flush-versus-scoop intake question was finally settled — and not in the exotic option’s favour.

Fitted later with F-86D-style tailpipes, the two aircraft flew on as NACA test and chase planes well into the mid-1950s, quietly supporting the development of the Century Series fighters — the F-101 through F-106 — before being scrapped. The escort fighter that never was had helped bring a whole generation of interceptors into being.

Sources: Joe Baugher, joebaugher.com; Wikipedia; Vintage Aviation News; NACA records.