Wednesday, January 10, 2018

The Grumman XF9F-9, Too Little, Too Soon

After the debacle of the XF10F Jaguar and the hasty conversion of the straight-wing F9F Panther to the swept-wing F9F Cougar, Grumman elected to propose the jet-powered equivalent of their F8F Bearcat to the Navy, encouraged to do so by BuAer's Fighter Class Desk. It was to be light, simple, inexpensive, maneuverable, and capable of near sonic speed in level flight without an afterburner. The engine selected was the Wright J65, a license-built British Armstrong Siddeley Sapphire that had also been selected to power the Navy's FJ-3 Fury and A4D Skyhawk. At the last moment, BuAer decided to add an afterburner in this instance.

Wright experienced difficulty in qualifying the afterburner so the first XF9F-9 made its first flight without one (it was subsequently redesignated F11F Tiger, since it bore no resemblance to its F9F Cougar forebear even in a dim light).

Like the Bearcat, it was relatively small and would have been wrapped snugly around its engine except that it was snugly wrapped with fuel tanks, not enough as it turned out.

Unfortunately, the F11F not only proved to be too small, lacking endurance, it was too soon, since the General Electric J79 then in development subsequently exceeded expectations as the afterburning Wright J65 was falling short of them. When evaluated with the J79, the F11F not only had terrific performance, it had somewhat better endurance. By then however, the Vought F8U Crusader had enough of a head start that the little Tiger became an also-ran.

A model of the first-flight prototype would be a relatively straight-forward conversion of a production F11F since most of the airframe was unchanged.
Note that the nose is even shorter than the original production F11F's but the wings, horizontal tail, and much of the fuselage is the same (the extreme aft fuselage has to be reshaped and shortened). Deletions include the wing fillet on the second production lot airplanes and the splitter plate ahead of the inlet (the inlet was offset from the fuselage, however). The vertical tail is smaller. Some other notable differences are the large pitot on the right side of the forward fuselage (it was subsequently moved to the vertical fin), the nose-landing-gear doors, the size of the wing fence, and the leading edge slat arrangement.