Lockheed AH-56 Cheyenne

The Lockheed AH-56 Cheyenne was an attack helicopter developed by Lockheed for the United States Army. It rose from the Army's Advanced Aerial Fire Support System (AAFSS) program to field the service's first dedicated attack helicopter. Lockheed designed the Cheyenne using a four-blade rigid-rotor system and configured the aircraft as a compound helicopter. It also featured low-mounted wings, a tail-mounted thrusting propeller, and a single General Electric T64 turboshaft engine. The Cheyenne was to have a high-speed dash capability to provide armed escort for the Army's transport helicopters, such as the Bell UH-1 Iroquois.

In 1966, the Army awarded Lockheed a contract for ten AH-56 prototypes. The AH-56's maiden flight took place on 21 September 1967. In January 1968, the Army awarded Lockheed a production contract, based on flight testing progress. A fatal crash and technical problems affecting performance put Cheyenne development behind schedule, resulting in the production contract being canceled on 19 May 1969. Development of the Cheyenne continued in the hope that the helicopter would eventually enter service.

On 9 August 1972, the Army canceled the Cheyenne program. Controversy with the United States Air Force over the Cheyenne's role in combat as well as the political climate regarding military acquisition programs had caused the Army to amend the service's attack helicopter requirements in favor of a twin-engined conventional helicopter, viewed as less technical and more survivable. The Army announced a new program for an Advanced Attack Helicopter (AAH) on 17 August 1972, which led to the development of the AH-64 Apache.