The Grumman F9F Panther was the first jet-powered aircraft to be built by Grumman, a long-time manufacturer of carrier-based fighter aircraft for the US Navy. The Panther bore the brunt of carrier-based jet fighter operations in the Korean War, and had the distinction of downing the first MiG-15 to be destroyed by a US Navy plane. However, it was to be in the ground attack role that the Panther was to gain its primary claim to fame.
As compared to some of its competitors, the Grumman Aircraft Corporation of Bethpage, Long Island was rather late in getting into the design of jet combat aircraft. However, between July of 1943 and November of 1944, Grumman undertook some preliminary work on several different jet-powered designs, some of them powered by a mixture of jet and piston engines. The first of these was the G-57, which was to have been powered by an R-2800 piston engine plus a small turbojet. Next was the G-61, which was a development of the F6F Hellcat with a turbojet engine in the tail. However, both of these projects had to be shelved in favor of higher-priority work on the G-58 (XF8F-1 Bearcat), a conventional piston-engined fighter. Later, Grumman began work on projects G-63 and G-71, which were both small single-jet designs. This was soon followed by the G-68, which was a single seat fighter to be powered by a TG-100 turboprop. However, none of these wartime projects attracted very much enthusiasm, and all of them were abandoned almost as soon as they were begun.
Serious Grumman work on jet-powered fighter aircraft did not really get underway until after the war was over. The G-75 was a postwar project begun by Grumman in September of 1945 in response to a Navy Request For Proposals for a two-seat radar-equipped jet-powered carrier-based night fighter. The G-75 was to be capable of flying at speeds of 500 mph and at altitudes of 40,000 feet and was supposed to be able to detect the presence of enemy aircraft at ranges as great as 125 miles. The G-75 looked very much like a jet-powered F7F Tigercat, and was to be powered by four 3000 lb.s.t. Westinghouse 24C-4B turbojets mounted two each side-by-side in midwing-mounted nacelles. A radome was to be mounted in the nose, and the armament was to have been four 20-mm cannon.
Competing proposals from Curtiss, Douglas, and Fleetwings were also submitted to the Navy in response to the RFP. On April 3, 1946, the Navy deemed the Douglas proposal as being the best of the lot, and ordered three prototypes under the designation XF3D-1. However, on April 11, a Navy contract was issued for the construction of two G-75 prototypes under the designation XF9F-1 as a backup just in case the Douglas design did not live up to expectations.
The XF9F-1 was appreciably larger and heavier than the XF3D-1. In the summer of 1946, further design studies indicated that the Grumman design was considerably less promising than the Douglas design, and the Navy considered cancelling the XF9F-1 contract altogether. ,p. This would ordinarily have been the end of the line, but Grumman had fortuitously been working on another totally-unrelated project under the company designation of G-79 that had been initiated only a month before the two XF9F-1 night fighter prototypes had been ordered. As originally conceived, the G-79 was a much smaller single-seat fighter powered either by a single centrifugal-flow turbojet fed by wing root intakes and exhausting underneath the rear fuselage, by two wing-mounted Westinghouse J34 axial-flow turbojets, or by two Rolls-Royce Derwent centrifugal-flow turbojets mounted in the wing roots. Alternatively, during the early summer of 1946, Grumman proposed the use of a single 5000 lb.s.t. Rolls-Royce Nene centrifugal-flow turbojet which would be built under license in the USA as the J42. In case the J42 ran into unexpected difficulties, the 4600 lb.s.t. Allison J33 was considered as a possible alternative, since it was about the same size as the Nene but was somewhat less powerful.
Enough interest was generated in this list of projects that the Navy was persuaded to amend the XF9F-1 contract rather than cancel it outright. On October 9, 1946, the XF9F-1 contract was amended to provide for the construction of three single-seat prototypes (BuNos 122475/122477), a static test airframe, plus design data for a swept-wing version. By November, the Navy had narrowed its choice of powerplant options and specified that two of the G-79 prototypes should be completed as XF9F-2 powered by Rolls Royce Nene turbojets and that the third should be powered by an Allison J33 turbojet and be designated XF9F-3.
The Rolls-Royce Nene jet engine, was to be built under license in the USA by the Taylor Turbine Corporation as the J42-TT-2. Just in case the adaptation of the Nene to production in the USA turned out to be more difficult than expected, Grumman developed a parallel version of the Panther to be powered by the Allison J33 turbojet. The J33 engine was somewhat less powerful than the J42, but it was considered to be a safer risk. The J33-powered version was to be designated F9F-3 and was to be manufactured in parallel with the J42-powered F9F-2.
Since the the J42 was not going to be ready in time to be installed in the XF9F-2, Taylor Turbine Corporation supplied six imported Rolls-Royce Nene turbojets to Grumman.
By the time that the mockup was ready for inspection in January and February of 1947, the G-79 design had been further revised. The cockpit had been moved further aft, the exhaust had been extended further to the rear, and the tail surfaces had been redesigned. The first XF9F-2 prototype (BuNo 122475) began engine ground running tests in October of 1947. The maiden flight took place from Bethpage on November 21, 1947, test pilot Corwin H. "Corky" Meyer being at the controls. The landing took place at Idlewild Airport (now the John F. Kennedy International Airport), since the runway at Bethpage was thought to be too short to risk a first landing of a jet-powered aircraft. The second XF9F-2 prototype (BuNo 122477) flew five days later.
Neither XF9F-2 prototype was fitted with armament nor was it fitted with an ejector seat. The wings folded upward hydraulically. A single tailhook retracted into the rear fuselage underneath the jet exhaust. Internal fuel capacity was 597 US gallons.
During company and Navy trials, the two XF9F-2 prototypes were found to snake markedly at all speeds and were longitudinally unstable at all speeds. The snaking problem was addressed by increasing the area of the fin and rudder, and the longitudinal instability problem was attacked by adding baffles to the fuel tanks. One of the prototypes shed its tail section during an arrested landing at Patuxent River, Maryland, which required some strengthening of the rear fuselage.
In February of 1948, non-jettisonable fuel tanks were added to the wingtips of the first prototype. This feature became standard with the 13th production aircraft, and non-jettisonable wingtip fuel tanks were to be a feature of the Panther through its entire production run.
Since the Navy was fearful that the Taylor Turbine Corporation might not be able to deliver sufficient numbers of engines in a timely fashion, the Navy encouraged Taylor to negotiate an agreement whereby the Nene manufacturing license would be transferred to a more-established engine manufacturing company. This was done as requested, and the Nene license was purchased from Taylor by Pratt & Whitney.