FLYING QUALITIES OF THE XV-5A V/STOL AIRCRAFT

The Army XV-5A lift-fan flight research aircraft is shown in hovering flight at Edwards Air Force Base, California, Figure 1. Accomplishments such as this were the results of V/STOL studies begun in the mid 1950's by the General Electric Company for the US Army. General Electric was to investigate the feasibility of the lift-fan concept for V/STOL propulsion application. An early result of this investigation was the development of the 5-foot-diameter lift fan, Figure 2. The lift fan was simply a low-pressure single-stage compressor driven by an integral impulse turbine attached to the fan blade tips. The installed design lift to thrust augmentation ratio was 2.78. Later a 3-foot-diameter pitch fan, which was a second generation scaled version of the original 5-foot-diameter fan, was developed for use as a pitch attitude control device on the yet-to-be-designed flight test vehicle. The power source for the newly developed lift-fan propulsion system was a pair of two-non-afterburning J-85-5 turbojet engines, Figure 3. The same basic engine with afterburner powers the NORATR T-38 and F-5 aircraft. The lift-fan concept included the attachment of diverter valves, Figure 4, to the discharge of each J-85-5 engine. These diverter valves direct the engine exhaust gages to either the lift fans or to conventional jet nozzles. The entire uninstalled system developed a measured 5,704 pounds of jet thrust or 15,850 pounds of fan lift at standard sea-level conditions. With hardware in hand, the lift-fan concept was well on its way to becoming a reality. The major advantage of this V/STOL propulsion concept was the common basic power source for both vertical and conventional flight. Early in 1961, USAAVNLABS requested a design competition to manufacture and test a lift-fan flight research aircraft to meet the following objectives: a. Determine performance and suitability of the lift-fan propulsion concept over a broad subsonic V/STOL flight spectrum. b. Demonstrate compatibility of the lift-fan system with a conventional, uncompromised, winged aircraft. c. Provide a useful vehicle for V/STOL research of a general nature such as studies of handling qualities, ground impingement, flight safety and other investigations.