Development of this unique aircraft - the world's first variable-sweep fighter, was begun in November 1946, to satisfy contractual requirements for the provision of design data for a swept-wing version of the XF9F-2/XF9F-3. As submitted on September 3, 1947, however, Design 83 already retained little but the forward fuselage, cockpit, and J42 turbojet of the F9F-2 and was proposed with clipped delta-wing, T-tail with swept surfaces, and conventional tail exhaust. Nevertheless, BuAer saw sufficient merit in the Design 83 proposal to issue letters of intent first in December 1947 to cover additional design work and then on April 7, 1948, to provide for the design and manufacture of two XF10F-1 prototypes. At that time, rather optimistically as it turned out, flight trials were projected to begin in August 1949. What followed was a long evolutionary gestation during which frequently changing Navy requirements and the selection of an unreliable powerplant (the Westinghouse J40 turbojet which was also the downfall of several other contemporary Navy projects) doomed this overly ambitious project.

In the three years between the issue of the letter of intent and December 1950, when Grumman and the Navy finally reached an agreement on the Detailed Specification for a new naval fighter, the design was entirely revised and the resulting design for a variable geometry aircraft ended without commonality with either the straight-wing F9F-2 or the original Design 83 proposal with a modified delta-wing.

All along, the project team, led by Gordon Israel, strove to design a carrier-based fighter capable of achieving the then-elusive twin goals of transonic speeds and good low-speed handling qualities. Difficult as it was, this task was further complicated by a steady stream of Navy-dictated changes and demands for radar, increased range, heavier armament, etc, which led to size and weight increases. In the process, to achieve the desired low-speed characteristics, Grumman first proposed the use of variable incidence wings in the fall of 1948 and finally proposed variable-sweep wings in July 1949.

As provided in the Detailed Specification issued in December 1950, the shoulder-mounted wings of the XF10F-1 were to translate hydraulically fore and aft by means of a single pivot-point to change sweep from a minimum of 13.5 degrees to a maximum of 42.5 degrees. The maximum sweep was to be used at the top-end of the performance envelope, and good low-speed handling characteristics were to be obtained by flying with the wings at the minimum sweep angle, and through the use of full-span slats and Fowler flaps extending over 80 percent of the trailing edge. Lateral control was to be provided by ailerons supplemented by spoilers and longitudinal control by a delta tailplane driven by a servoplane tab at the front of a long acorn fairing. The main undercarriage was to retract into the deep-bellied fuselage, beneath the compressor section of the engine. The Westinghouse J40 turbojet was to be fed by cheek intakes, and fuel tanks in the wings and fuselage were to have a total capacity of 1,573 gallons. In addition, a 300 gallon drop tank was to be carried beneath each wing on a swivelling pylon which remained parallel to the fuselage regardless of sweep angle. Production aircraft were to be fitted with an AN/APS-25 radar in the nose and armed with four 20-mm cannon in the forward fuselage and two rocket packs (each containing twenty-four 2.75-in FFARs or six 5-in HPAGs) or bombs of up to 2,000 lbs on swivelling wing pylons.

Even before the first prototype was completed, the future of the Jaguar appeared safely assured, as the outbreak of fighting in Korea brought with it a new urgency. In August 1950 the order for two prototypes to be powered by the 7,310/10,900-lb. military/afterburning thrust Westinghouse XJ40-WE-6 was supplemented by one for ten pre-production aircraft with either the XJ40-WE-6 or if available, the J40-WE-8. Later contracts were placed for 123 F10F-1s and eight F10F-1Ps, all to be powered by J40-WE-8s. However, after the Jaguar encountered overwhelming stability and control problems and its Navy-specified J40 engine proved totally inadequate, the entire program for what had been intended to be the world's first variable-sweep fighter had to be cancelled.

As the J40 program was already running behind schedule, no afterburning XJ40-WE-6 was available when the first XF10F-1 was completed. Thus this aircraft was fitted with a non-afterburning XJ40-WE-6 with an installed maximum thrust of only 6,800 lbs before undergoing systems checks and low-speed taxiing runs at Bethpage. On April 16, 1952, a Jaguar was partially dismantled and loaded aboard a Douglas C-124 to be airlifted to Edwards AFB, California, where initial trials of this advanced aircraft could be made safely over the Mojave Desert and away from prying eyes.

With Corwin H. 'Corky' Meyer at the controls, the first flight on May 19, 1952 lasted 16 minutes. It was marred by the failure of the slats to retract, excessive change in trim with flap movement, and rudder buffet. Two days later, the second flight ended with a dead stick landing due to a a defective electronic fuel control unit. As taxiing trials earlier had confirmed wind-tunnel and control-line tests predicting major longitudinal control difficulties with the initial horizontal tail design, it was painfully clear that the XF10F-1 trials were going to be anything but routine. Later tests revealed more airframe and engine problems. On the positive side, however, tests proved the wing sweep mechanism to be reliable and effective.

While Grumman had no control over engine-related deficiencies, the company did try to correct the numerous stability and control problems plaguing the trials. Noteworthy changes include the fitting of 'horsal' (horizontal ventral) fins on the rear fuselage sides, the testing of larger horizontal tail surfaces, and the substitution of powered F9F-6 swept horizontal surfaces for the originally fitted delta tailplane. The last of these changes appeared to hold much promise but nevertheless on April 1, 1953, the Navy cancelled production contracts. The subsequent grounding of all J40-powered aircraft spelled the end for the Jaguar. The second XF10F-1 prototype which was then 90 percent complete was shipped to the Naval Air Material Center in Philadelphia where, together with the first prototype, it was used for barrier testing.

When trials ended on April 25, 1953, with the thirty-second flight, the XF10F-1 had nevef been airborne for more than 67 minutes at a time. It had never reached an altitude of more than 31,500 ft. nor had it gone past Mach 0.86 in level flight as, fitted with a non-afterburning engine, it was grossly underpowered. Even with their intended afterburning engines, however, it is doubtful that production F10F-1s could have achieved predicated performance as their power loading would still have been higher than desired. Only one of the two XF10F-1s was completed.

Manufacturer: Grumman

Powerplant: One Westinghouse J40-WE-6 turbojet

Wingspan unswept: 50 ft 7 in

Wingspan swept: 36 ft 8 in

Length: 54 ft 5 in

Height: 16 ft 3 in

Weight empty: 20,426 lbs

Weight loaded: 27,540 lbs

Maximum speed: 710 mph

Cruising speed: 478 mph

Range: 1,670 miles

Service ceiling: 45,800 ft