The Grumman F9F/F-9 Cougar is a carrier-based jet-powered fighter aircraft designed and produced by the American aircraft manufacturer Grumman.
It was developed during the early 1950s on behalf of the United States Navy (US Navy) and United States Marine Corps (USMC), which were keen to quickly introduce a naval fighter equipped with a swept wing. Grumman's design team decided to adapt its earlier F9F Panther, replacing the straight wing of the Panther with a new swept wing. Thrust was also increased with the installation of a newer and more powerful engine. Nevertheless, the aircraft remained limited to subsonic speeds. The first prototype (XF9F-6), which was produced by modifying an existing Panther, performed its maiden flight on 20 September 1951. The Navy considered the Cougar to be an updated version of the Panther, despite having a different official name, and thus Cougars started off from F9F-6.
During December 1952, the F9F-6 was introduced to service, VF-32 being the first squadron to receive the type; while developed at a relatively rapid pace, the Cougar's arrival was too late for it to engage in active combat during the Korean War. While initial production aircraft were powered by a single Pratt & Whitney J48 turbojet engine, the F9F-7 were furnished by an Allison J33 powerplant instead. In the mid 1950s, the improved F9F-8 was introduced, which had a lower stall speed, improved handling when flown at high angles of attack, and increased range. The twin-seat F9F-8T was procured by the US Navy to perform various forms of training. The F9F-8P photo-reconnaissance variant was created by converting existing F9F-8s; most of the modifications were made to the aircraft's nose.
On 1 April 1954, US Navy Cougars established a new transcontinental crossing record. The US Navy's flight demonstration team, the Blue Angels, adopted the type in place of its Panthers. The Cougar gained a favourable reputation as a highly maneuverable and easy to fly aircraft. The only foreign air service that operated the Cougar was the Argentine Naval Aviation. The F9F-8 was withdrawn from front-line duties during the late 1950s, having been replaced by more capable aircraft such as the F11F Tigers and F8U Crusaders. While the Naval Reserves flew Cougars into the mid-1960s, only the TF-9J trainer model saw actual combat, having been deployed as a Forward Air Control aircraft during the Vietnam War. Following its withdrawal from active service, many F9F-6s were used as unmanned drones for combat training, designated F9F-6D, or as drone controllers, designated F9F-6K.
Design and development Early development Rumors that the Soviet Union had produced a swept wing fighter had circulated a year before the Mikoyan-Gurevich MiG-15 first appeared at air shows in 1949. Despite the level of activity taking place with swept wing aircraft, the US Navy was not initially focused on the development of such aircraft. This was largely because the US Navy's focus at the time was defending the battle group against high speed, high altitude bombers with interceptors, as well as escorting medium-range carrier-based bombers in all weather conditions; air-to-air combat was of less interest at that time. Nonetheless, the US Navy appreciated the importance of getting a capable carrier-based swept wing jet fighter. Grumman was awarded a contract for the development of a swept-wing fighter jet in early 1951. The arrival of the MiG-15, which easily outclassed straight-wing fighters in the air war over North Korea, was a major factor.Kinzey 1983, p. 4.Elward 2010, p. 112.Elward 2010, p. 113.
Development proceeded at a relatively rapid pace, in part due to Grumman's pre-existing experience of studying prospective derivatives of the Panther guiding several of their design choices. One example of this was the design team's decision to retain the center fuselage section of the Panther relatively unchanged, as studies of various alternative arrangements had been determined to have introduced center of gravity issues that in turn would have compelled substantial redesigns of other elements of the aircraft, including its propulsion. Instead, the aircraft shared the Panther's engine, landing gear, and various other systems. By changing as little as possible, the company was able to produce a swept wing fighter for the US Navy in mere months, rather than the years involved in delivering a clean-sheet design.Thomason 2008, p. 132.
However, it was necessary to implement various design changes. To effectively accommodate the switch from a straight wing to a swept one, it was necessary to delete the two 120-gallon tip tanks, as in combination with the swept wing there would have been too great a negative impact upon the aircraft's center of gravity; for the same reason, only a single hardpoint was fitted under each wing. Instead, internal fuel tanks housed within the wing were adopted, although these had less capacity than the tip tanks had. The leading edge flaps present on the Panther were deleted in favour of slats, while the trailing edge slats and fuselage-mounted flaps were both redesigned to be effective with the swept wing. The modified fuselage flaps could also function as a second set of air brakes.
Early flights
Three XF9F-6 prototypes, two airworthy and one static test airframe, were rapidly produced by modifying existing Panthers straight off the production line. On 20 September 1951, the first prototype conducted its maiden flight, piloted by Grumman test pilot Fred Rowley, only six months following the contract's awarding. Few meaningful problems were encountered during flight testing, most being quickly resolved or accepted on the basis of the perceived urgency for such an aircraft to be made available. The Cougar proved itself to be a definitive step forward; some pilots claimed the type to have superior handling at approach speeds than the preceding Panther.Thomason 2008, pp. 133-134. In a full-power vertical dive, it could break the sound barrier without experiencing buffeting or major undesirable flight characteristics.Thomason 2008, p. 134. In level flight, the aircraft remained only capable of subsonic flight, however, the critical Mach number was increased from 0.79 to 0.86 at sea level, and to 0.895 at 35,000 ft (10,000 m), thus delivering performance markedly superior to that of its predecessor.
However, both roll and pitch control were deemed to not satisfy the requirements. The original roll control arrangement, a combination of unboosted ailerons and hydraulically-actuated spoilers (referred to as "flaperons"), were insufficient when operated via mechanical linkage alone without hydraulic pressure, thus were redesigned. Wing fences were added and the spoilers extended from the fences to the tips of the wing, while the flaperons were divided into two halves, the inbound set being powered by a separate hydraulic system.
Pitch control was initially achieved via a conventional elevator and horizontal stabilizer, the rudder pedals controlled the section of the rudder beneath the horizontal tail surface, while the upper portion of the rudder was controlled by a yaw damper. However, this arrangement was unsuited to high speed flight, thus a powered "flying tail" was adopted.Thomason 2008, pp. 132-133. As such, the Cougar was capable of flying safely and easily even without the upper portion of the tail being present.Kinzey 1983, p. 5.
F9F-6
The initial production model was the F9F-6; a total of 646 airframes were delivered between mid-1952 and July 1954. The F9F-6 first flew on 20 September 1951, seven months after Grumman signed a contract with the Navy for swept-wing fighter.Kinzey 1983, p. 8. The engine was the Pratt & Whitney J42, a licensed version of the Rolls-Royce Nene. The first 30 production aircraft had the same J42 P-6 engine as the F9F-5; the rest had the more powerful J42 P-8 with of thrust.Elward 2010, p. 115.
Armament was four 20 mm (.79 in) AN/M3 cannons in the nose and provisions for two bombs or drop tanks under the wings. Most were fitted with a UHF homing antenna under the nose, and some were fitted with probes for inflight refuelling. The F9F-6 used an Aero 5D-1 weapons sight with an APG-30A gun-ranging radar. The F9F-6 was later designated F-9F in 1962. Sixty were built as F9F-6P reconnaissance aircraft with cameras instead of the nose cannon.Elward 2010, p. 128.
After withdrawal from active service, many F9F-6s were used as unmanned drones for combat training, designated F9F-6D, or as drone controllers, designated F9F-6K. The F9F-6K and the F9F-6D were redesignated the QF-9F and DF-9F, respectively.
F9F-7 The F9F-7 referred to the next batch of Cougars that were given the Allison J33 also found in the F9F-4, instead of the Pratt & Whitney J48. A total of 168 were built, but the J33 proved both less powerful and less reliable than the J48. Almost all were retrofitted with the J48 engine, and were thus indistinguishable from F9F-6s. These were redesignated F-9H in 1962.Elward 2010, p. 118.
Flexible deck testing The Navy used two modified F9F-7s to conduct experiments landing on British-inspired flexible decks which did not require the use of landing gear. The reasoning was that since an airplane's landing gear comprises some 33% of the total weight, a plane without landing gear would gain a greater range and would be able to carry more ordnance. The aircraft were fitted with a false bottom under the center fuselage to help balance the plane during landings on the flex-deck made up of a lubricated rubberized fabric. The deck, built by Goodyear was thick and featured several arresting cables.Elward 2010, p. 120. The planes were launched using a ramp and a handling dolly which served as temporary landing gear.Elward 2010, p. 119. The two F9F-7 aircraft in the test were equipped with the powerful J48-P8 engine instead of the Allison J33 engine originally used with the F9F-7. While the landing tests yielded positive results and proved that landing was clearly possible, the project was terminated in 1955 as it would have been difficult to move the aircraft around the carrier deck once they landed. It also required a highly skilled pilot to perform the landings and would have made it impossible to divert to a land base if necessary.Elward 2010, p. 122.
F9F-8