Staff Writer (Updated: 6/3/2016):
For the Grumman concern, who eventually earned the favor of the United States Navy when selling its collection of excellent fighter types - from the World War 2-era F4F "Wildcat" and F6F "Hellcat", to the Cold War-era F-14 "Tomcat" - the F9F "Panther" proved its first jet-powered fighter and the first such notable aircraft to the USN. The series went on to see extensive service throughout the Korean War (1950-1953) as a ground attack platform while scoring several air-to-air kills even against the famed Mikoyan-Gurevich MiG-15 "Fagot" swept-wing, single-seat fighter. The Panther formed a good portion of USN and USMC strength committed to the theater of war.
A swept-wing version of the F9F Panther was conceived in what would ultimately emerge as the F9F "Cougar" - the natural evolution of the Panther for it retained the same overall physical appearance of the former design, the major difference becoming its new swept-back wing design. While studies of such an aircraft were being drawn up as early as December 1945, it was not until March of 1950 that the USN officially commissioned Grumman with its development. Considering the success of the straight-winged Panther in the Korean War, the Cougar could be developed along much quicker lines around the already-proven airframe utilizing the same technology within. Grumman was handed the USN contract in March of 1951 and, by this time, the USN was firmly entrenched in Korea where its Panther would go on to record over 78,000 sorties in the conflict. The arrival of the swept-wing, Soviet MiG-15 fighter only spurred greater American military interest in similar swept-wing fighters which ultimately culminated in the war-winning North American F-86 "Sabre" series detailed elsewhere on this site.
Original Panthers were selected for modification and had swept-wing surfaces installed at their main spars and at the tail rudder. First flight of a modified Panther was achieved on September 20th, 1951. Each wing was given a sweep of 35 degrees and, unlike original Panthers, the prototype form lacked the wingtip fuel tanks. The new aircraft only retained the main-forward portion of the Panther's fuselage while the wings and some of the empennage were of largely new design. Wing roots were lengthened though retaining similar triangular intakes as on the Panther. These split intakes aspirated the single engine within and exhausted jointly through a single cylindrical exhaust port under the tail. The canopy carried the same "tear-drop" shape which offered excellent vision out of the cockpit. The single rudder assembly now showcased a pair of high-mounted, swept-back horizontal tail surfaces to complete the new appearance. The undercarriage remained retractable and featured two single-wheeled main legs and a single-wheeled nose leg. A tailhook was fitted under the tail which allowed for the requisite aircraft carrier-landing capabilities. The powerplant of choice became the Pratt & Whitney J48 series turbojet which also powered later Panther variants (F9F-5). With a special water/alcohol injection system, the aircraft could manage a thrust output of 7,250lbs.
Even as the Panther was already entrenched in the USN inventory by 1950, the service elected to procure the more modern F9F Cougar in some number - 1,392 in all. Its similarities and pedigree to the preceding Panther also led to the "F9F" designation being used by the USN for its newer Cougar line. The US Navy took on their first stock of Cougars in the latter part of 1952 as the "F9F-6" since the related F9F Panther variants ended at the "F9F-5" designation.
The Cougar line was born through three completed prototypes constructed and tested under the "XF9F-6" designation. Initial production models - the F9F-6 - totaled 646 examples. The F9F-6P was a dedicated photographic reconnaissance version sans its cannon armament and produced across 60 units. The F6F-6D was a "drone director" modified from retired F9F-6 production mounts. Drone directors born from F6F-6P recon models then became F9F-6PD. Retired F9F-6 fighters were also used as unmanned target drones under the F9F-6K designation, improved versions appearing as F9F-6K2.
Some 168 examples of the newer F9F-7 variant were produced and these were powered by the Allison J33 series turbojet engine which promoted a thrust output of 6,350lbs. However, many of these aircraft were eventually re-engined to take the standardized PW J48 turbojet in time as the J33 failed to make a wholly positive impression in practice.