The Lockheed AH-56 Cheyenne was a single-engine attack helicopter developed by Lockheed for the United States Army's Advanced Aerial Fire Support System (AAFSS) program to produce the Army's first dedicated attack helicopter. Lockheed designed the AH-56 utilizing a four-bladed rigid-rotor and configured the aircraft as a compound helicopter; with low-mounted wings and a tail-mounted thrusting propeller. The Cheyenne was powered by a GE T64 turboshaft engine and was intended to provide a 212-knot (244 mph, 393 km/h) dash capability in order to serve as an armed escort to the Army's transport helicopters, such as the UH-1 Iroquois.
In 1966, the Army awarded Lockheed a contract to develop 10 prototypes of the AH-56. The first flight of an AH-56 occurred 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. Cheyenne development 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.
The Cheyenne's compound helicopter design included a rigid main rotor, low-mounted wings, and a pusher propeller. The Cheyenne was powered by a General Electric T64 turboshaft engine. Thrust was provided by a pusher propeller at the rear of the aircraft. At high speeds, the amount of lift provided by the wings and thrust from the pusher prop, relieved the aerodynamic requirements of the rotor. At such speeds, the rotor produces 20% of the lift and could be adjusted by collective pitch control changes. The Cheyenne achieved speeds over 200 knots (230 mph, 370 km/h), but as a compound helicopter was unable to qualify for speed records in helicopter categories.
The Cheyenne had a two-seat tandem cockpit featuring an advanced navigation and fire control suite. The tandem seating placed the pilot in the rear seat, and the gunner in the front seat. An unusual feature of the gunner's station was that the entire seat, sighting system, and firing controls rotated to keep the gunner facing the same direction as the gun turret being controlled. The gun-sight afforded the gunner direct viewing from the turret by way of a periscope sight. The pilot had a helmet mounted sight system for aiming weapons.
Weapon turrets were mounted at the nose and the middle of aircraft underbelly. The nose turret had a +/- 100° of rotation from centerline and could mount either a 40 mm (1.57 in) grenade launcher, or a 7.62 mm (0.308 in) minigun. The belly turret included a 30 mm (1.18 in) automatic cannon with 360° of rotation. Mechanical stops prevented the belly turret from aiming at any part of the helicopter.
Six external hardpoints were located along the bottom of the helicopter, with two under each wing and two on the fuselage under the sponsons. The two inner wing hardpoints could carry pods of three TOW missiles. 2.75-inch (70 mm) rockets in 7-rocket, or 19-rocket launchers could be carried on the four wing hardpoints. The two fuselage mounts were dedicated to carrying external fuel tanks. The wing hardpoints could also be used to carry additional fuel tanks if needed.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 kn (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)
Armament
- Guns:
- 1 × nose turret with either an M129 40 mm (1.57 in) grenade launcher or an XM196 7.62x51 mm machine gun and
- 1 × belly turret with an XM140 30 mm (1.18 in) cannon
- Hardpoints: 6
- Rockets: 2.75 in (70 mm) FFA rockets
- Missiles: BGM-71 TOW missiles
