By Tommy H. Thomason

Sunday, February 15, 2009

Area Rule

The area rule for transonic drag minimization was postulated and demonstrated by NACA engineer Richard Whitcomb. The rule was that the total cross-sectional area of an airplane should smoothly increase and then decrease. The result was that the fuselage cross section needed to be reduced beginning at the point of attachment of the leading edge of the wing and indented as necessary to compensate for the cross sectional area of the wing at each successive fuselage station going aft. The theory was provided to U.S. aerospace contractors in a confidential Research Memorandum in September 1952.

As it happened, Grumman had already defined and proposed an area-ruled fighter design to the Navy in December 1951. The result was the sleek F11F Tiger. Grumman went so far as to design special area-ruled external wing tanks for the Tiger.

Unfortunately, the engine chosen, the license-built Armstrong-Siddeley Sapphire, did not meet specified thrust. Although supersonic, the airplane fell well short of the guaranteed top speed. Performance with the substituted engine, the General Electric J79, was excellent but the Navy chose to standardize on the 1,000 mph F8U Crusader. Tiger production ended with only 201 built. After a very brief operational career with a handful of carrier-based squadrons, most of these were relegated to a training role. It also served for several years as the mount for the Blue Angels flight-demonstration team.


Overscan said...

I thought the original Tiger design wasn't area-ruled until Grumman got hold of the NASA research - at least thats how NASA tells it.

Tailspin said...

NASA might tell it that way, but Grumman's proposal for the "Sapphire Cougar" in December 1951 not only depicts an area-ruled airframe, but includes a chart showing the smooth increase of the cross-sectional area of the fuselage and wing by longitudinal fuselage station. See page 211 of U.S. Naval Air Superiority.