Military


AH-56A Cheyenne
Advanced Aerial Fire Support System (AAFSS)

The AH-56 Cheyenne Advanced Aerial Fire Support System (AAFSS) was a prototype attack helicopter developed to replace the AH-1 Cobra. It never went into production. The Army -- in cooperation with industry -- began developing the AH-56 Cheyenne and the AH-64 Apache during the final years of the Vietnam conflict. The Army's development of specifically designed attack helicopters during the 1970s again raised the question of Army and Air Force aerial missions. By this time, the Air Force was content to permit the Army to continue developing helicopters.

The experience of Vietnam showed that the existing attack helicopter, the AH-1 Cobra, was vulnerable even to light antiaircraft fire and lacked the agility to fly close to the ground for long periods of time. The AH-56A Cheyenne helicopter was intended to correct those deficiencies. The Lockheed AH-56A Cheyenne attack helicopter was designed to meet the US Army's requirement for the Advance Aerial Fire Support System (AAFSS). The helicopter's mission would eventually be assumed by the Boeing (formerly McDonnell Douglas) AH-64 Series Apache attack helicopter.

Termed a compound helicopter, the Cheyenne had rotor blades as well as stub wings and a pusher propeller. The rotors provide conventional helicopter performance, and in conjunction with the stub wings and pusher prop permit level flight at speeds of more than 250 miles per hour. The Cheyenne was the first Army aircraft to be designed and built as an integrated aerial vehicle / armament / avionics / fire control gun ship and coincidentally the first compound helicopter to be developed by any of the US military forces. The versatile craft, when fully equipped, would be capable of firing machine guns, grenades, rockets and missiles. The swiveling belly turret mounts a 30-mm automatic gun. Both the pilot and gunner are protected by armor plate.

The AH-56 was essentially a flying tank built around rigid rotor system. This remarkable compound helicopter relied on a pusher propeller and a set of wings to achieve speeds greater than 322 kph (200 mph). The AH-56A was a compound helicopter designed to perform the advanced aerial fire support mission. The Cheyenne had a single rigid four-bladed main rotor and anti-torque tail rotor, and a three-bladed pusher. In addition to a single four-bladed "rigid" main rotor and a teetering four-bladed antitorque tail rotor, a three-bladed pusher propeller was located at the aft end of the fuselage, and a low wing was located on the fuselage midsection. During high-speed forward flight, the main rotor was partially unloaded with the lift provided by the wing and thrust supplied by the pusher propeller. The cockpit had tandem seals. Normally, the forward seat was for the copilot/gunner, and the aft seat was for the pilot. The conventional wheel-type landing gear was retractable.

Provisions for wide variety of armament systems are available in two turrets and on six external stores stations. The rigid-rotor Cheyenne featured a XM112 swiveling gunner's station linked to rotating belly and nose turrets, and a laser range-finder tied to a fire control computer. It was armed with an XM52 30mm automatic gun in the belly turret and a XM51 40mm grenade launcher or a XM53 7.62mm Gatling machine gun in the chin-turret, TOWs, and XM200 2.75 inch rocket launchers.

The Cheyenne, powered by one General Electric T64-GE-16 3435 shp turbine engine, was designed to fly at nearly twice the speed of combat helicopters used in Vietnam. The AH-56A had a maximum speed of 214 knots, cruise speed of 197 knots, a service ceiling of 26,000 feet, maximum range of 547 nautical miles, and could climb 3,420 feet per minute. Designed for quick turn-around capability, an AH-56A returning from a combat flight could be readied and rearmed for a new mission within ten minutes. A complete engine change could be accomplished in 30 minutes. The AH-56 was a very promising aircraft, but the program was cancelled. There did not appear to be a clearly defined capability gap which would require the Cheyenne helicopter, This issue may be amplified in view of the fact that the Army was expected to procure TOW missile modification kits for its current Cobra attack helicopters.

If the Army had to introduce an attack helicopter into a mid-intensity war situation against a well-equipped enemy it would be a first for this kind of aircraft. Meanwhile there were sensitive problems, such as aircraft survivability and weapon systems effectiveness, which required intensive study, testing, and evaluation before confident estimates can be made about its combat expectations, To our knowledge, however, there are no plans to conduct extensive realistic testing of the aircraft before a decision was made to enter it into full-scale production.

The Cheyenne was expected to carry about three times the useful weapon load of the Army's current attack helicopter and the fuel requirements of the Cheyenne would also be greater. These factors, among other things, may require additional cargo helicopters and/or ground vehicles to adequately resupply the Cheyenne in the forward combat area. We found no evidence that these logistical support requirements, including their expected financial impact on the Army's budget, had been adequately determined on the basis of the various battle scenarios.

Without contesting the concept of forward basing of the Cheyenne, there appeared to be a need to assess the expected requirements for maintaining forward-base secrecy and security. There may be a need to employ a substantial ground force, including air defense elements, to forward-base the aircraft [as in fact was the case with the AH-64 Apache deployment in the Kosovo conclict in 1999].

The aircraft experienced control-system problems with its initial configuration. The problems were found and ultimately fixed, but not fast enough to satisfy the Department of Defense and the US Army. Lockheed’s inability to successfully scale up its XH-51 by a factor of five to its AH-56 led the Army to cancel the Cheyenne production program in 1969 because of unresolved technical problems. Lockheed itself was experiencing problems in several other major program areas. The outcome was a new start by the US Army that yielded the Hughes AH-64 Apache and ultimately, in 1995, the merger of the Lockheed Corporation with Martin Marietta.



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