User:Born2flie/AH-56 Cheyenne
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| AH-56 Cheyenne | |
|---|---|
 AH-56 Cheyenne during testing |
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| Type | Attack helicopter |
| Manufacturer | Lockheed |
| Maiden flight | 21 September 1967 |
| Status | Cancelled |
| Number built | 10 |
| Developed from | XH-51 |
The Lockheed AH-56 Cheyenne was a two-seat, single-engine, rigid-rotor, compound helicopter with low-mounted, fixed wings and retractable main landing gear. The AH-56A was the design winner of the United States Army's Advanced Aerial Fire Support System program in 1965 to establish a technologically advanced, dedicated attack helicopter. It was armed with a 30mm cannon in a belly turret and either a 7.62 minigun or a 40mm grenade launcher in a nose turret. It was also capable of being armed with 2.75-inch rockets and TOW missiles. The Cheyenne's compound helicopter design was intended to provide a 212-knot dash capability in order to serve as an armed escort to the Army's transport helicopters, such as the UH-1 Iroquois.
Lockheed was awarded a production contract in 1967 but was unable to deliver production aircraft by 1968, and the production contract was subsequently canceled in 1969. Development continued in the hopes that eventually the Army would be able to field the Cheyenne. A 1972 congressional report from the Senate which recommended funding of the United States Air Force's A-10 and the United States Navy's Harrier programs sounded the end for the AH-56, and the program was canceled by the Secretary of the Army in August 1972.
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[edit] History
Prior to the development of the AH-56, all armed helicopters had been modifications or derivatives from existing aircraft whose design purpose was other than carrying weapons for aerial employment.[1] In 1962, instigated by then Secretary of Defense McNamara, the Howze Board envisioned an airmobile division that was supported by 90 armed aircraft,[2] at the same time the Army was preparing to deploy its first armed escort helicopters to Vietnam, 15 UH-1A Iroquois modified with armament systems capable of mounting machine guns and rockets.
Another development that would ultimately influence the direction of armed helicopters happened that year when Bell Helicopters presented a new helicopter design, the D-255 Iroquois Warrior, to the Army in the hopes of soliciting funding for further development. The D-255 would be a purpose-built attack aircraft based on the UH-1B airframe and dynamic components with a nose-mounted ball turret, a belly-mounted gun pod, and stub wings for mounting rockets or SS-10 anti-armor missiles.
Soon after, and possibly influenced by viewing the D-255 design, Army officials decided to go with an interim, commercial off-the-shelf (COTS) aircraft to fulfill the escort role until the Army could decide what they really wanted in a dedicated armed helicopter. In December 1962, Combat Development Command (CDC) drafted a Qualitative Material Requirement (QMR) for an aircraft with a 140–knot cruise speed and a 1,500-pound payload, anticipating the potential of the D-255. However, the Secretary of the Army disapproved the interim approach and directed that the Army look for a more advanced system that would dramatically improve over current helicopter designs.[1]
[edit] Fire-support Aerial System
Based on the guidance from the Secretary of the Army, CDC established Qualitative Material Development Objectives (QMDO) for a rotary-wing aircraft with 195-knot cruise speed, 220-knot dash speed, and the capability to hover out-of-ground-effect (OGE) at 6,000 feet on a 95 °F (35 °C) day. The Director of Defense Research and Engineering (DDRE) agreed with the changes but required that all efforts be exhausted to determine if existing systems could be improved to meet the requirement.
Meanwhile, Army Material Command (AMC) conducted feasibility studies on the QMDO, and established a Program Manager office for the Fire-support Aerial System (FAS) based on the QMDO. AMC made a recommendation based on the study to narrow the competition to compound helicopters, as they were the only rotary-wing aircraft currently capable of approaching CDC's stated objectives. In March 1964, the Secretary of the Army advised DDRE that modification of existing systems would not approach the required performance of the FAS program; the Army would continue using UH-1B aircraft until development of the FAS could proceed. On 26 March 1964, the Army Chief of Staff redesignated the FAS program as the Advanced Aerial Fire Support System (AAFSS).
[edit] Advanced Aerial Fire Support System
The QMDO document for the AAFSS was approved in April 1964, and on 1 August 1964, the Transportation Research and Engineering Command contacted 148 prospective contractors with a request for proposals (RFP). Bell submitted the D-262, a modification of the D-255, but still a conventional helicopter design. Sikorsky submitted the S-66, which featured a "Rotorprop" serving as a tail rotor but during increased speeds would rotate 90° to serve as pusher prop.[3] Lockheed submitted the CL-840 design, a rigid-rotor compound helicopter with both a pushing propeller and a conventional tail rotor mounted at the end of the tail. On 19 February 1965, Lockheed and Sikorsky were announced as winners of Project Definition Phase contracts.[1]
Each company assembled proposals for the design in three configurations based on the QMDO and a revised RFP, based on a draft QMR. The proposals were then studied by an evaluation board and submitted with recommendations to the selection authority council on 6 October 1965. On 3 November 1965, Lockheed was announced as the winner of the AAFSS program selection, but it wasn't until 23 March 1966 that Lockheed was awarded the contract for engineering and development of the Advanced Aerial Fire Support System.
[edit] Development
On 23 March 1966 the Army awarded Lockheed an engineering and development (ED) contract for ten prototypes, designating the aircraft AH-56A. Lockheed began construction of the aircraft at its Van Nuys, California facility. 15 months later, on 3 May 1967, Lockheed held a roll-out ceremony for the AH-56A, and the aircraft was christened Cheyenne by the Army.
The first flight of the AH-56 was accomplished by 21 September 1967 with the second prototype aircraft. Lockheed and the Army later held a 13-minute demonstration "first flight" for the public at the Van Nuys Airport on 12 December 1967. During the flight, the aircraft demonstrated the new capabilities brought about by the thrusting propeller. For instance, the helicopter could hold a 10-degree nose-high or nose-low attitude while hovering. The helicopter could also slow down or accelerate without pitching the nose up or down.
Flight testing and envelope expansion progressed with minor issues, such as an instability when the aircraft was flying in ground effect. But these problems were quickly addressed and on 8 January 1968 the Secretary of Defense approved $31.4 million to initiate a production order for an initial 375 aircraft. By March 1968, the AH-56 had established a flight envelope of 169 knots (195 mph, 314 km/h) in forward flight, 23.9 knots (27.5 mph, 44.3 km/h) sidewards, and 20 knots (23 mph, 37 km/h) rearwards.
[edit] Source information
The Cheyenne (AH-56A) was conceived as an integrated aerial weapons system, a high-speed and heavily armed helicopter to escort airmobile forces and provide direct fire support. Following award of the production contract, technical difficulties arose in the prototype aircraft. On 19 May 1969, when it appeared that production schedules would not be met with aircraft that would meet performance specifications, the production contract was terminated by the Army for default. As the year closed, the Cheyenne program was being evaluated to determine a course of action that would make maximum use of the work to date.
--Source
The Cheyenne helicopter project is an example in weapon system acquisition of the problems of cost, contract performance, performance specification, and technical risk. In fiscal year 1966 the Army contracted with the Lockheed Aircraft Corporation for the development of an advanced aerial fire support system. The central component of the system is the Cheyenne helicopter (AH-56). Pursuant to an option clause in the development contract, a separate contract was negotiated on January 8, 1967, for the production of 375 aircraft. On May 19, 1969, the production contract was terminated by the Army for default. Lockheed appealed to the Armed Services Board of Contract Appeals, alleging that the Army erred and claiming an estimated $150 million as damages. The appeal, pending as the year closed, should be acted upon in fiscal year 1971. The Army formed a litigation group under the supervision of the General Counsel to present the Army's case.
Meanwhile, the development program continued during fiscal year 1970 and considerable progress was reported in resolving most of the technical problems that caused termination of the production contract. On March 3, 1970, however, Lockheed stated that it had exhausted its operating capital because of the size of its claims against the Department of Defense under this and other contracts and requested the Office of the Secretary of Defense (OSD) to provide relief pending settlement of the claims. As the year closed, the request was receiving careful study by the Office of the Secretary of Defense. The Army was particularly concerned with the effects of possible OSD action on further Cheyenne development and upon its plans eventually to purchase the advanced aerial fire support system. A decision on procurement of Cheyennes was deferred. The deferment will permit additional development and further evaluation of alternatives. The Lockheed financial request and the Cheyenne program received wide publicity.
--Source
Following award of the production contract, technical difficulties arose in the prototype aircraft. On May 19, 1969, when it appeared that production schedules would not be met with aircraft that would meet performance specifications, the production contract was terminated by the Army for default. As the year closed, the Cheyenne program was being evaluated to determine a course of action that would make maximum use of the work to date.
--Source
[edit] Program demise
[edit] Design
The AH-56 has a short but substantial wing on each side of the airframe and a rigid main rotor. Thrust is provided by a pusher-prop at the rear of the aircraft. Since the main rotor is not relied on for the full amount of lift (provided by the wings) or thrust (from the pusher prop), the Cheyenne is able to reach high speeds in excess of 200 knots.
The oddest feature of the AH-56 is the gunner's station. Like the AH-1 Cobra, the AH-56 has two crewmembers, seated in tandem—a pilot and a gunner. The AH-56 gunner's station seat rotates along with the turret to keep the gunner facing the same direction as the 30mm cannon, viewing the target through direct-view optics.
[edit] Specifications (AH-56A)
{{aero-spec}}
Data from {Jane's Aircraft}[4]
General characteristics
- Crew: 2 pilots: 1 pilot, 1 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)
- Disc area: ft² (m²)
- Empty weight: 12,215 lb (45,540 kg)
- Loaded weight: 18,300 lb (8,300 kg)
- Useful load: lb (kg)
- Max takeoff weight: 25,880 lb (11,739 kg)
- Powerplant: 1× General Electric T64-GE-16 turboshaft, 3925 shp (kW)
Performance
- Maximum speed: 212 knots (244 mph, 393 km/h)
- Cruise speed: 195 knots (225 mph, 362 km/h)
- Range: 1,063 nm (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)
[edit] References
- ^ a b c An Abridged History of the Army Attack Helicopter Program. Washington, DC: Office of the Assistant Vice Chief of Staff of the Army, Department of the Army. 1973. <http://www.webcitation.org/5JNGWqTeh>.
- ^ Bonin, John A., MAJ, USA. Towards the Third Dimension in Combined Arms: The Evolution of Armed Helicopters into Air Maneuver Units in Vietnam. Fort Leavenworth, Kansas: Command and General Staff College. 1986. <http://www.webcitation.org/5Tb9iX8u2>.
- ^ Apostolo, Giorgio. The Illustrated Encyclopedia of Helicopters. New York: Bonanza Books. 1984. ISBN 9780517439357
- ^ Jane's All the World's Aircraft, 1969-70. Ed. John W. R. Taylor. London: Sampson, Low, Marston & Co. 1969.
- Robb, Raymond L. "Hybrid helicopters: Compounding the quest for speed", Vertiflite. Summer, 2006. American Helicopter Society.
- Shrader, Cecil L., COL (Ret.), USA. "Attack Helicopter Transformation". Letter to the editor. ARMY Magazine. January 2003. Association of the United States Army.
