In 1938, the Grumman Corporation proposed a new high-performance fighter to the United States Navy. The new aircraft was to combine the greatest amount of engine power with the smallest possible airframe. In the interest of greater power, Grumman even proposed a twin-engine design, a first for the company. The resulting aircraft was the XF5F Skyrocket. The Grumman XF5F Skyrocket was based around the concept of adding a secondary engine to an aircraft that would be no larger than a typical single-engine fighter. The airframe was small, initially being under 10,000lbs when fully loaded. This airframe was powered by two 1,200hp Wright Cyclone engines. The choice of two engines enabled some interesting design features. The XF5F had its landing gear retract into the engine nacelles, improving strength and reducing weight. The aircraft also had a very short fuselage that actually began well behind the leading edge of the ring. This arrangement provided exceptional visibility that surpassed single-engine fighters. Most importantly, the two engines were designed to rotate in opposite directions. This caused the engines to cancel each other's torque, improving stability and flight performance considerably. In addition, the close spacing of the engines meant that the aircraft remained stable in the event it had to fly on one engine only. The first and second photos show the initial XF5F Skyrocket. Initial flight testing in 1940 was promising, but further changes were needed. Enhancements were made, including the installation of four .50 caliber machine guns into the central fuselage, a change that required the fuselage to be extended forward of the wing's leading edge. The redesigned XF5F can be seen in the second photo. Due to the modifications, the new XF5F was slightly heavier than intended, now tipping the scales at 10,900lbs (4,955kg). However, performance did not suffer. Indeed, the Skyrocket had performance that could only be described as blistering. Immediately after its modifications were made, the US Navy organized a flyoff between the Skyrocket and several aircraft, many of which were prototypes themselves. The contenders for the 1941 test included: - The Grumman XF5F Skyrocket - The Grumman F4F Wildcat - The Prototype Vought XF4U Corsair - The Bell XFL Airbonita (A navalized P-39) - The Brewster F2A Buffalo - The Bell P-39 Aircobra - The Curtiss P-40 Warhawk - The Hawker Hurricane - The Supermarine Spitfire Testing revealed the Skyrocket to be superior to all of its competitors in the most important attributes. The XF5F displayed acceleration and a rate of climb that made it the superior carrier-based interceptor. During the tests, the XF5F repeatedly left its competitors in its wake during races. The visibility provided was especially enjoyed, making the aircraft a star during simulated carrier landings. Unfortunately, while the XF5F was determined to be the best aircraft so far as flight performance went, the Navy was less enthusiastic about the logistical impact. Double the engines meant double the maintenance and faster depletion of spare parts aboard aircraft carriers. For this reason, the Navy chose to pursue a single-engine fighter. Grumman continued developing the XF5F, adding further improvements and other modifications into 1942. During this time, they also began developing an even more powerful twin-engine fighter. This new fighter was the XF7F. The XF5F program was then abandoned, but the XF5F was used to gather flightdata to help its younger, larger brother during development. This continued to the very end of 1944 when the XF5F was finally grounded after suffering damage during a belly landing. Though the XF5F was lost, it helped create the Grumman F7F Tigercat, considered by many to be the greatest of Grumman's propeller driven fighters.