Grumman F9F-6 "Cougar"

F9F-6 "Cougar: of Fighter Squadron 112 (VF-112) during field carrier landing practice at NAS Miramar.
This aircraft is being flown by Ensign Robert Jellison, USNR

ABOUT THE GRUMMAN F9F-6 "COUGAR"

History

Grumman received a Navy contract on 16 December 1946 to produce a jet powered, straight wing, carried based fighter. The aircraft Grumman proposed first flew on 21 November 1947 and was eventually designated and named the F9F-2 Panther. It was first delivered to Navy squadron in May 1949 and remained in service until October 1958. The Navy accepted a total of 1,388 Panthers with designations of F9F-2, F9F-3, F9F-4 and F9F-5.

The Panther’s success led Grumman to design a swept wing derivative and propose it to the Navy.

The new design retained the fuselage of the Panther but included a swept wing and tail. The Navy awarded Grumman a contract for this new aircraft on 2 March 1951. It made its first flight on 20 September and was named the Cougar but retained the F9F designation. The Cougar was first delivered to the Navy in November 1952 and remained in squadron until February 1960. The Navy accepted a total of 1,985 Cougars with the designations F9F-6, F9F-7 and F9F-8.

Concept to production

The surprise appearance of the swept-wing MiG-15 in November 1950 suddenly rendered obsolete the straight-wing Grumman F9F-2 and McDonnell F2H-2, the Navy's most advanced fighters then in squadron service. Work on a swept-wing Panther, which had been shelved because of the poor low-speed behavior of swept-wing aircraft. was resumed on a high priority basis.

A contract for the modification of three F9F-5 airframes was awarded in March of 1951, and the F9F-6 prototype first flew six and a half months later The first F9F-6s were delivered to VF-32 in November 1951, just one year after the MiG- I5's debut in Korea.


Ensign Bob Jellison

Airframe

Conceived as a straightforward derivative of the Panther, the F9F-6 retained the fuselage, vertical tail surfaces, power plant, and undercarriage of the F9F-5 and was fitted with wings swept at 35 degrees at quarter chord and with swept horizontal tail surfaces. To compensate for the increase in approach and stalling speeds resulting from the use of swept wings, the chord of the leading-edge slats and that of the trailing-edge flaps were increased and much larger split flaps were fitted beneath the center section. Other modifications included the lengthening of the forward fuselage by 2 ft, the forward extension of the intake-housing wing center section, the enlargement of the wing root fillets, and the use of a broader chord lower rudder section linked to the rudder pedals and of an upper rudder section of unchanged dimension but linked to a yaw damper. Furthermore, as the tip tanks had to be dispensed with, the resulting reduction in fuel capacity was made up partially by increasing the size of the forward fuselage fuel tank and adding bladder-type tanks in the wing Ieading-edge. (Nevertheless, total internal fuel capacity decreased from 1,003 to 919 US gal.)

Controls

The first prototype had cotiventional horn-balanced ailerons for lateral control and conventional tab geared elevators for longitudinal control. However, with these surfaces, the F9F-6 experienced control reversal at high speed and poor lateral and longitudinal control. The use of an hydraulically-operated 'flying tall' easily cured the longitudinal control deficiency but lateral control remained unsatisfactory until the horn balanced ailerons were replaced by' flaperon/'flaperette' spoilers fitted on the wing upper surface at about 75 per cent of the chord line. The flaperon was ahead of the flaperette and under normal flight conditions both of these spoiler sections were hydraulically operated as a single surface. In an emergency, the flaperette section was operated independently by means of a separate hydraulic System. Large fences were also added during trials to inhibit spanwise flow and preserve lateral control effectiveness. The resulting F9F-6 demonstrated better carrier handling characteristics than the F9F-5, while critical Mach number was increased from 0.79 to 0.86 at sea level and to 0.895 at 35,000 ft. 

Photo F9F-6P being launched from port catapault

F9F-6 "Cougar: of Fighter Squadron 112 (VF-112) landing on the USS Kearsarge
Note the 12 arresting wires on this straight deck carrier.

Trials to delivery

In spite of the need to develop and evaluate these major control system changes, and much to the credit of the Grumman engineering team, flight trials proceeded remarkably quickly and production F9F-6s were ready for squadron delivery only fourteen months after the first flight of the prototype. Equally impressive were the ease with which this stop-gap design was further developed and its longevity.

Field carrier landing practice at NAS Miramar