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This article is about the single-engine models of the Bell Cobra family. For the twin-engine models, see Bell AH-1 SuperCobra. For an overview of the whole Huey family of aircraft, see Bell Huey family.

The Bell AH-1 Cobra (company designation: Model 209) is a two-blade, single engine attack helicopter manufactured by Bell Helicopter. It was developed using the engine, transmission and rotor system of the Bell's UH-1 Iroquois. The AH-1 is also referred to as the HueyCobra or Snake.

The AH-1 was the backbone of the United States Army's attack helicopter fleet, but has been replaced by the AH-64 Apache in Army service. Upgraded versions continue to fly with the militaries of several other nations. The AH-1 twin engine versions remain in service with United States Marine Corps (USMC) as the service's primary attack helicopter. Surplus AH-1 helicopters have been converted for fighting forest fires. The United States Forest Service refers to their program as the Firewatch Cobra. Garlick Helicopters also converts surplus AH-1s for forest firefighting under the name FireSnake. Development Background Closely related with the development of the Bell AH-1 is the story of the Bell UH-1 Iroquois—predecessor of the modern helicopter, icon of the Vietnam War and one of the most numerous helicopter types built. The UH-1 made the theory of air cavalry practical, as the new tactics called for US forces to be highly mobile across a wide area. Unlike before, they would not stand and fight long battles, and they would not stay and hold positions. Instead, the plan was that the troops carried by fleets of UH-1 "Hueys" would range across the country, to fight the enemy at times and places of their own choice.[3] It soon became clear that the unarmed troop helicopters were vulnerable against ground fire from Việt Cộng and North Vietnamese troops, particularly as they came down to drop their troops in a landing zone. Without friendly support from artillery or ground forces, the only way to pacify a landing zone was from the air, preferably with an aircraft that could closely escort the transport helicopters, and loiter over the landing zone as the battle progressed. By 1962 a small number of armed UH-1As were used as escorts, armed with multiple machine guns and rocket mounts.[4] The massive expansion of American military presence in Vietnam opened a new era of war from the air. The linchpin of US Army tactics were the helicopters, and the protection of those helicopters became a vital role.[5] Iroquois Warrior, Sioux Scout and AAFSS Bell Model 207 Sioux Scout Main article: Bell 207 Sioux Scout Bell had been investigating helicopter gunships since the late 1950s, and had created a mockup of its D-255 helicopter gunship concept, named "Iroquois Warrior". In June 1962, Bell displayed the mockup to Army officials, hoping to solicit funding for further development. The Iroquois Warrior was planned to be a purpose-built attack aircraft based on the UH-1B components with a new, slender airframe and a two-seat, tandem cockpit. It featured a grenade launcher in a ball turret on the nose, a 20 mm belly-mounted gun pod, and stub wings for mounting rockets or SS.10 anti-tank missiles.[6] The Army was interested and awarded Bell a proof of concept contract in December 1962. Bell modified a Model 47 into the sleek Model 207 Sioux Scout which first flew in July 1963. The Sioux Scout had all the key features of a modern attack helicopter: a tandem cockpit, stub wings for weapons, and a chin-mounted gun turret. After evaluating the Sioux Scout in early 1964, the Army was impressed, but also felt the Sioux Scout was undersized, underpowered, and generally not suited for practical use.[7] Army's solution to the shortcomings of the Sioux Scout was to launch the Advanced Aerial Fire Support System (AAFSS) competition.[7] The AAFSS requirement gave birth to the Lockheed AH-56 Cheyenne, a heavy attack helicopter with high speed capability. It proved to be too sophisticated, and was canceled after 10 years of development in 1972. The Army sought greater survivability in a conventional attack helicopter.[7] Model 209 Bell 209 prototype of the AH-1 Cobra series, with skids retracted (FAA no. N209J) At the same time, despite the Army's preference for the AAFSS–for which Bell Helicopter was not selected to compete–Bell stuck with their own idea of a smaller and lighter gunship.[7] In January 1965 Bell invested $1 million to proceed with a new design. Mating the proven transmission, the "540" rotor system of the UH-1C augmented by a Stability Control Augmentation System (SCAS), and the T53 turboshaft engine of the UH-1 with the design philosophy of the Sioux Scout, Bell produced the Model 209.[7] Bell's Model 209 largely resembled the "Iroquois Warrior" mockup.[8] In Vietnam, events were also advancing in favor of the Model 209. Attacks on US forces were increasing, and by the end of June 1965 there were already 50,000 US ground troops in Vietnam.[7] 1965 was also the deadline for AAFSS selection, but the program would become stuck in technical difficulties and political bickering. The U.S. Army needed an interim gunship for Vietnam and it asked five companies to provide a quick solution. Submissions came in for armed variants of the Boeing-Vertol ACH-47A, Kaman HH-2C Tomahawk, Piasecki 16H Pathfinder, Sikorsky S-61, and the Bell 209.[7] On 3 September 1965 Bell rolled out its Model 209 prototype, and four days later it made its maiden flight, only eight months after the go-ahead. In April 1966, the model won an evaluation against the other rival helicopters. Then the Army signed the first production contract for 110 aircraft.[7] Bell added Cobra to the UH-1's Huey nickname to produce its HueyCobra name for the 209. The Army applied the Cobra name to its AH-1G designation for the helicopter.[9] The Bell 209 demonstrator was used for the next six years to test weapons and fit of equipment. It had been modified to the match AH-1 production standard by the early 1970s. The demonstrator was retired to the Patton Museum at Fort Knox, Kentucky and converted to approximately its original appearance.[8] Into production The Bell 209 design was modified for production. The retractable skids were replaced by simpler fixed skids. A new wide-blade rotor was featured. For production, a plexiglass canopy replaced the 209's armored glass canopy which was heavy enough to harm performance.[8] Other changes were incorporated after entering service. The main one of these was moving the tail rotor from the helicopter's left side to the right for improved effectiveness of the rotor.[10] The U.S. Marine Corps was interested in the Cobra and ordered an improved twin-engined version in 1968 under the designation AH-1J. This would lead to more twin-engine variants.[11] In 1972, the Army sought improved anti-armor capability. Under the Improved Cobra Armament Program (ICAP), trials of eight AH-1s fitted with TOW missiles were conducted in October 1973. After passing qualification tests the following year, Bell was contracted with upgrading 101 AH-1Gs to the TOW-capable AH-1Q configuration.[12] Following AH-1Q operational tests, a more powerful T53 engine and transmission were added from 1976 resulting in the AH-1S version. The AH-1S was upgraded in three steps, culminating with the AH-1F.[7][13]