AH-56A Cheyenne - Program History
In the early 196Os, the Army was seeking ways to improve conventional helicopter capabilities. In 1963 the Secretary of the Army "disapproved the concept of modifying existing aircraft to provide only an interim solution to the direct fire support helicopter requirement" and directed the Army to "lift its sights" and develop an optimized aerial weapon system. The APL56A Cheyenne helicopter was the result of that directive.
After several studies, analyses, and contractor competition, in March 1966 the Army awarded a fixed-price incentive contract for engineering development to the Lockheed California Company. The contract included production options for 375, 500, 1,000, and 1,500 aircraft. The Army exercised the first option in January 1968, There were several technical problems, however -- most of them concerned with the main rotor control system. In Nay 1969, after Lockheed failed to convince the Army that the problems could be corrected within a reasonable time, the Army terminated the production part of the contract for contractor default. The development part of the contract remained in force, however, and certain performance specifications were subsequently downgraded.
Lockheed rolled-out the first prototype on May 3, 1967. The Army's newest and most advanced combat helicopter, the AH-56A Cheyenne, demonstrated its speed, versatility, and maneuverability in December 1967 during its first public flight at Van Nuys, California. Observers at the demonstration included ranking military and U. S. Government officials, representatives of the prime contractor, Lockheed-California Company, and some 800 sub-contractors who helped build the technologically advanced rotocraft.
Because of the advanced technologies in the AH-56 Cheyenne, the program ran into serious delays and cost overruns. The Cheyenne experienced developmental difficulties with some of the new technology it employed. Thus, Congress was severely critical of the program. However, advocates of the AH-56 Cheyenne argued that the program was about to succeed, but it would still take several years for this aircraft actually to go into the field and help soldiers on the ground. Eventually, Lockheed had eliminated nearly all of the bugs but the Cheyenne languished under an awkward procurement process put in place by Secretary of Defense Robert McNamara.
Unfortunately, what was a straight forward concept for a new armed helicopter soon became bogged down in a morass of permutations, modifications and additions to its design. The technicians had taken over from the tacticians. The concept grew in complexity and cost. Worse, it was being pushed into a later time frame when it was sorely needed in combat. Such things as a rigid rotor, ground avoidance radar, inertial navigation and computerization were straining the state of the art and pricing the Army out of mass production. A reevaluation was inevitable.
The production contract was canceled during the fiscal year 1969 because of technical problems. The development program was still in effect, however, and an early solution to technical problems was expected. There were no firm plans to enter into another production contract at the time production was cancelled.
By 1969 development activity had been centered around integrating subsystems and testing an improved rotor control system. Simultaneously the Army and Lockheed were negotiating a restructured development program (minus any production options), and on August 17, 1971, they entered into a new contract to continue development.
Lockheed-California Co. said it had remedied virtually all problems of the AH-56A compound helicopter cited in a cure notice from the Army in 1969. The restructured AH-56A development program identified two Army test programs which were to be conducted by the US Army Aviation Systems Test Activity (USAAS A) on the Improved Control System (ICS) configuration of the AH-56A. These programs were the Army Preliminary Evaluation I (APE I) and a portion of the Research and Development Acceptance Test I (RDAT I).
The Army Preliminary Evaluation I and a portion of the Research and Development Acceptance Test I were conducted periodically on the AH-56A Cheyenne compound helicopter by the US Army Aviation Systems Test Activity between 30 January and 23 December 1971. These engineering tests were divided into five distinct phases to permit Army evaluation of the aircraft at various stages of the contractor development program. Primary test objectives were to gather stability and control data to provide an early assessment of the AH-56A, to assist in determining flight envelopes for future Army tests, and to examine previously identified problem areas.
None of the rotor dynamic instabilities previously encountered in the contractor's development program were noted during these tests. Lateral control migration with airspeed was not objectionable. The capability of the pusher propeller to provide rapid deceleration and to control airspeed independently of dive angle was an excellent feature.
Five deficiencies and 54 shortcomings were identified. The deficiencies are (1) excessive pilot workload due to unacceptable static lateral-directional stability characteristics at low airspeed seriously impairs the capability to operate at minimum altitudes unaffected by conditions of darkness or adverse weather, (2) uncommanded aircraft motion and loss of control during some maneuvering flight conditions, (3) rapid rate of rotor speed decay following simulated engine failures which allows the rotor speed to drop below the present transient limit, (4) inadequate directional control margins in sideward flight, and (5) excessive vibration levels in portions of the flight envelope.
Correction of the deficiencies would be a prerequisite for an airworthiness it release for operational Army aviators, and correction of the shortcomings was desirable. Two deficiencies warranted a reduction of the flight envelope size for future Army tests until correction of those deficiencies was accomplished. Further testing of the AH-56A was recommended.
The US Army Aviation Systems Test Activity (USAASTA) conducted an Attack Helicopter Evaluation of the AH-56A Cheyenne Compound Helicopter during the period 15 April to 15 June 1972. The AH-56A was tested at Yuma Proving Ground, Arizona and Mammoth Lakes, California. This evaluation was conducted to provide data for use in determining Advanced Aerial Fire Support System effectiveness model inputs, validating material need requirements, and validating contractor claims. The forward area concealment evaluation was conducted by the US Army Combat Developments Command Aviation Agency and the maintenance characteristics evaluation was conducted by the US Army Aviation Systems Command. The performance and handling qualities testing consisted of 49 test flights totaling 42.2 flight hours. The pusher propeller was a major contributor to several enhancing performance and handling qualities characteristics.
By the end of 1971 the Cheyenne was in engineering development being readied for production, and a new production decision (for budgetary purposes) was anticipated early in 1972. A production contract, however, was not expected to be signed before October 1972. The Army in September 1971 estimated that the weapon system acquisition cost would total about $2.1 billion, or about $4.5 million for each aircraft.
By the time the aircraft was ready for production in 1972, the Army was becoming interested in a helicopter with night and all-weather attack capability - a requirement that was not included in the Cheyenne contract. Congress then cancelled the program at a significant financial loss to Lockheed. Ten prototypes were completed before the program was terminated August 9, 1972 due to delayed development, rising costs, and the appearance of two competitive company-funded initiatives by Sikorsky and Bell. Most Cheyenne airframes ended up at Aberdeen Proving Grounds.
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