The Lockheed AH-56 Cheyenne was a purpose-built attack helicopter. It was developed to meet a US Army requirement for a first dedicated attack helicopter. The US Army was looking for an advanced helicopter design. In 1966 Lockheed was awarded a contract for 10 prototype helicopters, which would be used for trials and evaluation. Design of the AH-56 was very futuristic, innovative and ambitions for its time. The helicopter made its first flight in 1967. The Cheyenne had impressive performance and devastating ƒιяєρσωєя. However because of technical problems, excessive weight, cost overruns and the change of military vision, the project of AH-56 Cheyenne was canceled in 1972.

The Cheyenne used Lockheed rotor system, tail-mounted pusher propeller, and conventional tail rotor. The tail section was pointing down. Short wings provided good lift and high speeds and put the Cheyenne in the list of compound helicopter class. This machine was powered by a single General Electric T64-GE-16 engine. During flight most of the engine power went to the pusher propeller, and only 20-25% of power was delivered to the main rotor. This gave a top speed of about 390 km/h and ability to reach such speed at extremely low altitudes. Currently such design and is still used only on experimental helicopters.

The Cheyenne was armed with new for the time TOW wire-guided anti-tank missiles. Helicopter had wing hardpoints and could carry 6 of these missiles. It was also fitted with a side-mounted 30 mm cannon. The cannon could easily destroy lightly-armored vehicles. Nose-mounted turret of the AH-56 was fitted with 7.62 mm minigun, or alternatively a 40 mm ɢяєиα∂є launcher. This helicopter could also carry pods with 70 mm unguided rockets. Inbord hardpoints could carry additional fuel tanks for extended range.

The AH-56 had a crew of two. The huge transparent canopy gave a superb all around visibility to the pilot and the gunner. Pilot could also ƒιяє all ωєαρσиs of the Cheyenne. Helicopter was fitted with advanced ƒιяє control and navigation suite.

In 1972 the US Army initiated a new program for a more conventional attack helicopter. This program led to the development of the AH-64 Apache, which entered service in 1986. As an interim helicopter the AH-1 Cobra was used. Ultimately an experimental Piasecki X-49A SpeedHawk with pusher propeller has been developed. This concept aircraft made its first flight in 2007 and is intended to test maximum speed and possible increase in payload capacity.

Source: http://www.military-today.com/helicopters/ah_56_cheyenne.htm