Lockheed AH-56 Cheyenne Mystery Cache

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 with low-mounted wings and a tail-mounted thrusting propeller driven by a 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, but as a stopgap also ordered the simpler AH-1G Cobra as an interim attack aircraft for combat in Vietnam. 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 cancellation of the production contract on 19 May 1969. Development of the Cheyenne continued in the hope that the helicopter would eventually enter service.

But as American involvement in Vietnam was winding down, the Army canceled the Cheyenne program on 9 August 1972. By this time, the AH-1 Cobra was widely deployed by the Army during the Vietnam War. 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-engine 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.

General characteristics:

• Crew: Two; one pilot, one copilot/gunner (front seat)
• Length: 54 ft 8 in (16.66 m)
• Rotor diameter: 51 ft 3 in (15.62 m)
• Height: 13 ft 8.5 in (4.18 m)
• Empty weight: 12,215 lb (5,540 kg)
• Loaded weight: 18,300 lb (8,300 kg)
• Max. takeoff weight: 25,880 lb (11,740 kg)
• Powerplant: 1 × General Electric T64-GE-16 turboshaft, 3,925 shp (2,930 kW)
• Rotor systems: 4 blades on main rotor, 4 blades on tail rotor, 3 blades on pusher propeller

Performance:

• Maximum speed: 212 knots (244 mph, 393 km/h)
• Cruise speed: 195 knots (225 mph, 362 km/h)
• Range: 1,063 nmi (1,225 mi, 1,971 km)
• Service ceiling: 20,000 ft (6,100 m)
• Rate of climb: 3,000 ft/min (15.23 m/s)