The Lockheed AH-56 Cheyenne was slated to become the world's fastest production attack helicopter, with a speed of just over 250 mph. It was conceived in 1966 as a heavily armed, extremely maneuverable escort helicopter.

Rather than depend on its rotor for lift, thus limiting its top speed, the AH-56 had a 26 foot wing that supported the helicopter at speed. With its wing, the Cheyenne was classified as a compound rotorcraft, rather than a true helicopter. Its rotor was feathered during high speed runs, with forward thrust provided by a propeller in the tail.

Armament consisted of either a 7.62 mm minigun or 40 mm grenade launcher in the nose, a 30 mm cannon under its mid-section, anti tank missiles and rockets under its wing. The weapons system was computer assisted using doppler radar and laser imaging. For extended range, two fuel tanks could be mounted under the fuselage.

The Cheyenne had a crew of two, sitting in tandem, with the pilot in the rear cockpit seat, and the gunner/co-pilot up front. This arrangement provided excellent all around visibility for the gunner.

The main landing gear of the helicopter was lengthened in order to have enough ground clearance for its 30 mm cannon turret. The landing gear retracted into the wing. A wheel under the rear fin supported the tail. With a full load, it was intended that the Cheyenne use a short take off roll to get into the air.

When the first Cheyenne prototype took to the sky with successful results in September of 1968, a total of 375 AH-56 production helicopters were ordered by the U.S. Army. However, further testing showed that the helicopter had stability problems when flown at speeds in excess of 200 mph.

On March 12, 1969 the main rotor of a prototype came into contact with its aft fuselage resulting in a fatal crash. A wind tunnel test of a second prototype in September of 1969 found that the problem still was not cured and resulted in significant damage to the aircraft. Nevertheless, prototype testing continued through August 9, 1972 when the project was canceled. It was over cost, stability problems were never fully resolved, and by this time, more advanced, less costly, but slower helicopters were already on the drawing board.

Ten Lockheed AH-56 Cheyenne helicopters were produced.  All were prototypes.  Four can be seen on display at museums around the United States.

Specifications
Primary Function:     Crew:     Engine:     Horsepower:     Length:     Height:     Rotor Diameter:     Weight Empty:     Max. Weight:     Cruise Speed:     Max. Speed:     Initial Climb:     Ceiling:     Range:     First Flight:     Year Deployed:	escort/attack two P&W T64-GE-16 3,922 h.p. 54' 8" 13' 9" 51' 3" 11,740 lbs. 25,880 lbs. 225 mph 252 mph 3,000 fpm 20,000 feet 2,800 miles 9/21/67 -------