Lockheed AH-56 Cheyenne

AH-56 sur Wikipedia.en

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The Lockheed AH-56 Cheyenne was a single-engine [Vous devez être inscrit et connecté pour voir ce lien] developed by [Vous devez être inscrit et connecté pour voir ce lien] for the [Vous devez être inscrit et connecté pour voir ce lien]'s Advanced Aerial Fire Support System (AAFSS) program to produce the Army's first dedicated attack helicopter.

Lockheed designed the AH-56 utilizing a four-bladed rigid-rotor and configured the aircraft as a [Vous devez être inscrit et connecté pour voir ce lien]; with low-mounted wings and a tail-mounted thrusting propeller.

The Cheyenne was powered by a [Vous devez être inscrit et connecté pour voir ce lien] turboshaft engine and was intended to provide a 212-knot (244 mph, 393 km/h) dash capability in order to serve as an armed escort to the Army's transport helicopters, such as the [Vous devez être inscrit et connecté pour voir ce lien].

In 1966, the Army awarded Lockheed a contract to develop 10 prototypes of the AH-56.

The first flight of an AH-56 occurred on 21 September 1967.

In January 1968, the Army awarded Lockheed a production contract, based on flight testing progress.

A fatal crash and technical problems affecting performance put Cheyenne development behind schedule, resulting in the production contract being canceled on 19 May 1969.

Cheyenne development continued in the hope that the helicopter would eventually enter service.

On 9 August 1972, the Army canceled the Cheyenne program.

Controversy with the [Vous devez être inscrit et connecté pour voir ce lien] over the Cheyenne's role in combat as well as the political climate regarding military acquisition programs had caused the Army to amend the service's attack helicopter requirements in favor of a twin-engined conventional helicopter, viewed as less technical and more survivable.

^{[Vous devez être inscrit et connecté pour voir ce lien]}The Army announced a new program for an [Vous devez être inscrit et connecté pour voir ce lien] on 17 August 1972,^{[Vous devez être inscrit et connecté pour voir ce lien]} which led to the development of the [Vous devez être inscrit et connecté pour voir ce lien].

Development

Background

Prior to the development of the AH-56, all armed helicopters had been modifications to existing aircraft designed for unarmed uses.

In 1962, then [Vous devez être inscrit et connecté pour voir ce lien] convened the [Vous devez être inscrit et connecté pour voir ce lien] to review Army aviation requirements.

The results of the board envisioned an airmobile division that was supported by 90 armed aircraft.

The recommendation of the Howze Board came at the same time the Army was preparing to deploy its first armed escort helicopters to Vietnam, 15 [Vous devez être inscrit et connecté pour voir ce lien] modified with armament systems capable of mounting machine guns and rockets.
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In June 1962, Bell Helicopter presented a new helicopter design to Army officials, in the hopes of soliciting funding for further development.

The [Vous devez être inscrit et connecté pour voir ce lien] was envisioned as a purpose-built attack aircraft based on the [Vous devez être inscrit et connecté pour voir ce lien] airframe and dynamic components, with a nose-mounted ball turret, a belly-mounted gun pod, and stub wings for mounting rockets or [Vous devez être inscrit et connecté pour voir ce lien].

Attack helicopter requirements


In December 1962, Combat Development Command (CDC) drafted a Qualitative Material Requirement (QMR) for an interim, [Vous devez être inscrit et connecté pour voir ce lien] (COTS) aircraft, with a 140–knot (161 mph, 259 km/h) cruise speed and a 1,500-pound (680 kg) payload.

This was seen as an attempt by Army officials, anticipating the potential of the D-255, to acquire an interim aircraft to fill the escort role until the Army could determine the requirements for a dedicated armed helicopter.

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.
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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 (224 mph, 361 km/h) cruise speed, 220-knot (253 mph, 407 km/h) dash speed, and the capability to [Vous devez être inscrit et connecté pour voir ce lien] (OGE) at 6,000 feet (1,830 m) on a 95 °F (35 °C) day.

The speed requirements were derived from the speed of aircraft the helicopter would escort.

The Director of Defense Research and Engineering (DDRE) conditionally approved the changes to the development objectives, pending his review of the proposed program.

He also directed the Army to determine whether or not any other helicopter could offer an improvement in performance over the UH-1B in the meantime.

As a result, the Army Material Command (AMC) conducted a study to determine if the development objectives were feasible and also established a Program Manager's office for the Fire-support Aerial System (FAS).

AMC recommended to narrow the competition to compound helicopters, as they were considered the only helicopter configuration at the time capable of being developed to meet the objectives.

In March 1964, the Secretary of the Army advised DDRE that modification of existing aircraft 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.


AAFSS competition


On 26 March 1964, the Army Chief of Staff redesignated the FAS program as the Advanced Aerial Fire Support System (AAFSS).

The development objectives document (QMDO) for the AAFSS was approved in April 1964, and on 1 August 1964, the [Vous devez être inscrit et connecté pour voir ce lien] 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 [Vous devez être inscrit et connecté pour voir ce lien], which featured a "Rotorprop" that would serve as a tail rotor but as speeds increased would rotate 90° to act as pusher propeller.

Lockheed submitted the CL-840 design, a [Vous devez être inscrit et connecté pour voir ce lien] compound helicopter with both a pushing propeller and a conventional tail rotor mounted at the end of the tail
The Army announced Lockheed and Sikorsky as winners of Project Definition Phase contracts on 19 February 1965.^{[Vous devez être inscrit et connecté pour voir ce lien][Vous devez être inscrit et connecté pour voir ce lien]}

Meanwhile, the Army also continued to pursue a solution for an interim aircraft for combat in Vietnam until the AAFSS could be fielded, resulting in development of the [Vous devez être inscrit et connecté pour voir ce lien].