The Lockheed XF-90 was a design for a penetration fighter, capable of escorting bombers and carrying out ground attack missions, but never got beyond the prototype stage.
In July 1945, with the P-80A in production, Lockheed’s jet design team led by Kelly Johnson began to look at more advanced designs, attempting to take advantage of captured German research. The company was thus in a good position to attempt to meet an Air Force requirement for a penetration fighter, first issued in 1946. The new aircraft was expected to serve as a bomber escort and a ground attack aircraft.
Unfortunately for Lockheed, the Air Force couldn’t decide what it wanted the new aircraft to be able to do. Originally they required a combat range of 900 miles. This then rose to 1,500 miles before dropping to 600 miles. Rate of climb went from an original 10 minutes to 35,000ft up to under five minutes to 50,000ft.
Despite these problems, Lockheed received a contract for two XP-90 prototypes on 20 June 1946. The original design was for a delta-wing fighter, but wind tunnel tests revealed problems with this design, and it was replaced with a twin engined swept wing design.
The new Model 90 was to be powered by two Westinghouse J34 engines, which were small enough to fit side by side within the fuselage. It had swept wings, a pointed nose and was to be armed with six 20mm cannon. The fuselage had a flat base and curved sides, and was the same width for most of its length. It used a new stronger aluminium alloy, and in order to allow it to carry out ground attack missions was very solidly built.
The first XF-90 prototype, powered by two 3,000lb thrust Westinghouse XJ34-WE-11 engines, made its maiden flight on 3 June 1949. The trial programme was completed without any serious problems, but the aircraft was underpowered and its performance was disappointing. The second prototype was completed with XJ-34-WE-15 engines that produced 3,600lb thrust normally or 4,200lb thrust with afterburners. These engines were later installed on the first prototype.
The XF-90 was significantly heavier than its main rival, the McDonnell XF-88, but used the same engines. Even with the more powerful engines, the XF-90 was still slower than the North American F-86A Sabre, which was already in service. As a result Lockheed put forward a series of alternative designs, two using single engines and one using two engines. In each case the new engines would have required a major redesign, so in June 1950 the McDonnell XF-88 Voodoo was chosen for further development. The XF-90 project was cancelled in September 1950. The first prototype was later used for structural tests, while the first was destroyed in the Frenchman’s Flat atomic bomb tests of 1952.
The XF-88 never entered service, but it was the basis of the F-101 Voodoo supersonic jet fighter.
Engines: Westinghouse XJ-34-WE-15
Power: 3,600lb thrust normally or 4,200lb thrust with afterburners each
Wing span: 40ft
Length: 56ft 2in
Height: 15ft 9in
Empty weight: 18,050lb
Loaded weight: 27,200lb
Maximum weight: 31,060lb
Maximum speed: 668mph at 1,000ft
Cruising speed: 473mpg
Climb: 4m 30sec to 25,000ft
Service ceiling: 39,000ft
Normal range: 1,050 miles
Maximum range: 2,300 miles