The AH-56 Cheyenne had a maximum speed of approximately 351 km/h (218 mph). While this was fast for a helicopter at the time, it did not surpass the top speeds of more modern attack helicopters like the AH-64 Apache or the Mi-24 Hind.

The AH-64 Apache, developed in the 1970s, has a top speed of around 293 km/h (182 mph). The Mi-24 Hind, which entered service in the 1970s, has a top speed of approximately 335 km/h (208 mph).

It’s important to note that top speeds can vary depending on factors such as altitude, weather conditions, and aircraft configuration. However, based on generally accepted figures, the AH-56 Cheyenne does not hold the title of the fastest combat helicopter in the world.

The AH-56 Cheyenne was born at the request of the US military that needed a high-speed combat helicopter to maneuver quickly on the battlefield. This project was started in the 1960s with the winner being Lockheed. The AH-56 Cheyenne is a perfect combination of light helicopter and attack aircraft. It was arguably the world’s most advanced attack helicopter in its heyday, with revolutionary features far beyond its time.

Unfortunately, the Cheyenne program never fully succeeded due to technical issues, program management shortfalls, changing procurement priorities, high cost, and a crash in 1969 that left a test pilot ᴅᴇᴀᴅ. Despite never entering service, the Cheyenne left a profound impact on the concept of close air support and attack helicopter design, and today holds a special place in military aviation history.

The AH-56A was also called the Advanced Aerial Fire Support System. During the period when the United States was building up its troop strength in Vietnam, the AH-56 became a bold attempt to compete with the Air Force for a key role in air-to-ground support. The Cheyenne was a highly sophisticated compound rotorcraft incorporating design features pioneered in Lockheed’s earlier XH-51A test ship.

It was a long, slim helicopter with retractable landing gear, small wings that spanned almost 27ft, and a General Electric T64-GE-16 shaft turbine engine with a four-bladed rotor. The power rating of the engine was increased to 3,922hp as the test program evolved. The Cheyenne used an innovative propulsion system built around the T64. The power plant drove a rigid, four-bladed, gyro-stabilized main rotor, the tail-mounted anti-torque rotor, and the pusher propeller at the extreme end of the tail boom.

The Army was looking for a truly giant leap with the AH-56. The service established exceedingly ambitious goals. It said it wanted an aircraft with a top speed of 220kt, able to hover out of ground effect at 6,000ft, with a ferry range of 2,100 nautical miles. A little noticed feature of the Cheyenne was its ability to self-deploy over long distances, including the 2,200-mile flight from California to Hawaii. Although Lockheed had little experience building helicopters, the Army chose its design in 1966.

The crew of two, pilot and gunner, sat in tandem in an enclosed cockpit. The impressive armament of the Cheyenne included a 30mm XM140 cannon in a belly turret, and a 40mm XM129 grenade launcher or 7.62-mm minigun in a nose turret. Under the wing were six hard points for ordnance, consisting of Hughes TOW anti-tank missiles or 2.75in folding fin aircraft rockets.

The AH-56 had an advanced ωєαρσи sighting system that included night vision equipment and a helmet gun sight. The Army was enthusiastic enough that in January 1968, it placed an initial production order for 375 aircraft. As it turned out, only ten Cheyennes were built. But in tests the AH-56 had difficulty maintaining stability close to the ground and at high speed. Various design changes seemed to help, but no certain fix had been found when the third Cheyenne built was lost in a crash on Mar. 12, 1969.

Following the grounding of the AH-56s, tests resumed in July 1969. By then the Army had abandoned its production order – prematurely, many observers said. The Cheyenne program had also suffered from cost increases. Meanwhile, the Army was getting good results with a less advanced, less ambitious helicopter, the AH-1G Huey Cobra, which went into combat in South Vietnam in October 1967.

Had its technical difficulties been overcome and had politics not intervened, the Cheyenne would have been a formidable ωєαρσи. In some ways, it was more advanced than today’s AH-64D Longbow Apache, which offers some of the capabilities the Cheyenne had but is not as effective at high altitude. The Cheyenne “was an incredible aircraft,” said Richard Berch, who piloted the AH-56A at the Yuma Proving Ground in Arizona. “It would have changed military aviation.