The Lockheed AH-56A Cheyenne’s ability to self-deploy over great distances, including the 2,200-mile journey from California to Hawaii, was a little-noticed feature of the aircraft
The Lockheed AH-56A Cheyenne assault helicopter, which would have transformed warfare, was tested by the Army in the 1960s. A civilian version might have revolutionized aviation. Instead, the Cheyenne became a “might have been,” as James C. Goodall explains in his book 75 Years of the Lockheed Martin Skunk Works. It was expensive and technically challenging. It might have been too sophisticated for its era. One pilot described it as occasionally “spectacular” in flight, but there were some small flaws that were never completely worked out.
The Advanced Aerial Fire Support System (AAFSS) was another name for the AH-56A aircraft. The AH-56 was a daring attempt to compete with the Air Force for a crucial role in air-to-ground support during the time when the United States was increasing the number of its troops in Vietnam. The Cheyenne was a very complex compound rotorcraft that used cutting-edge design elements from Lockheed’s earlier XH-51A test ship.
It had long, thin wings that extended almost 27 feet, retractable landing gear, a General Electric T64-GE-16 shaft turbine engine, and a four-bladed rotor. The engine’s power rating was raised to 3,922 horsepower as the test program progressed. The T64 served as the center of Cheyenne’s innovative propulsion system. A pusher propeller at the very end of the tail boom, a tail-mounted anti-torque rotor, and a stiff, four-bladed, gyro-stabilized main rotor were all driven by the power plant.
The main and anti-torque rotors received all of the power during vertical and hovering flight, whereas the pusher propeller received all but around 700sph during forward flight. The main rotor and windmilling stub wings produced lift during forward flight. The AH-56A was capable of sea-level speeds of more than 275mph in a “clean” configuration.
With the AH-56, the Army was seeking a truly significant leap. The service set incredibly ambitious objectives. It declared that it required a plane with a maximum speed of 220kt, the ability to hover without ground effect at a height of 6,000 feet, and a ferry range of 2,100 nautical miles. The Cheyenne’s ability to self-deploy over vast distances, including the 2,200-mile journey from California to Hawaii, was a little-noticed capability. The Army adopted Lockheed’s design in 1966 even though it had little prior experience producing helicopters.
The cockpit was enclosed, and the two-person crew—a pilot and a gunner/co-pilot—sat adjacent to one another. The Cheyenne had a 40mm XM129 grenade launcher or 7.62-mm minigun in the nose turret in addition to a 30mm XM140 cannon in the belly turret. Six hard points for armament, which might be Hughes TOW anti-tank missiles or 2.75-inch folding fin aviation rockets, were located under the wing. A helmet gun sight and night vision equipment were also part of the AH-56’s advanced weapon sighting system.
The Army was so enthusiastic that it placed an initial production order for 375 aircraft in January 1968. In the end, just ten Cheyennes were produced. On September 21, 1967, test pilot Donald R. Segner took the AH-56 prototype for its initial flight at Van Nuys Airport with Army Lt. Col. Emil “Jack” Kluever in the cockpit. However, in tests, the AH-56 had trouble maintaining stability at high speeds and near the ground. When the third Cheyenne constructed was destroyed in a crash on March 12, 1969, some design adjustments appeared to have helped, but no definitive solution had been established.
Testing resumed in July 1969 after the AH-56s were grounded. By that point, the Army had prematurely canceled its production order, according to many analysts. Cost hikes also affected the Cheyenne program. The AH-1G Huey Cobra, which saw action in South Vietnam in October 1967, was a less sophisticated and less ambitious helicopter that was performing well for the Army at the time.
The Cheyenne would have been a powerful weapon had its technical issues been resolved and politics not gotten in the way. It was more advanced in some aspects than the AH-64D Longbow Apache of the present day, which has some of the same capabilities as the Cheyenne but is less efficient at high altitudes. Richard Berch, who flew the AH-56A at the Yuma Proving Ground in Arizona, described the Cheyenne as “an incredible aircraft.”
“It would have changed military aviation. A passenger carrying version would have changed short-haul commercial aviation.”
75 years of the Lockheed Martin Skunk Works is published by Osprey Publishing and is available to order here.
Photo by: William Pretrina via Wikipedia and U.S. Army
