Armed helicopter

An armed helicopter is a military helicopter equipped with aircraft ordnance. Most commonly, it is used for attacking targets on the ground. Such a helicopter could be either purposely designed for a ground-attack mission—in which case it would be more specifically categorized as an attack helicopter—or may have been previously designed for other uses, such as utility, air cargo, aerial reconnaissance, etc., with the weapons mounts being modifications, rather than part of the design of the helicopter. The purpose of the modification to an armed helicopter configuration can be field expediency during combat, the lack of military funding to develop or purchase attack helicopters, or the need to maintain the helicopter for missions that do not require the weapons.

Specialized armed helicopters fly from ships at sea, and are equipped for anti-submarine warfare or strikes with anti-ship missiles.

Direct fire support delivered by weapons mounted on helicopters began informally in the Korean War, with United States Marines firing their weapons from the open doors of the aircraft, into the treeline of the landing area below. The concept evolved with the French during the Algerian and the First Indochina wars, in the form of armed helicopters; where utility, cargo, and observation military helicopters were modified to carry various weapons.

The French Army was one of the first military forces to modify and use helicopters in combat in a ground attack role during the Algerian War of 1954–62. In 1955, French field commanders placed infantry machine gunners in the stretcher panniers of their Bell 47 (Sioux H-13) casualty evacuation helicopters. The ad hoc gunships were used to reach FLN guerrilla positions on otherwise inaccessible mountain ridges and peaks, but were far too underpowered.

In 1956, the French Air Force experimented with arming the Sikorsky S-55, then being superseded in service by the more capable Piasecki H-21 and Sikorsky CH-34 helicopters. The H-19 was originally fitted with two rocket launchers and an ex-Luftwaffe MG 151/20 20-mm cannon, both mounted axially on the outside of the aircraft. Later, an MG151/20 cannon, two .50 cal. (12.7-mm) Browning machine guns, and an FN Browning 7.5-mm light machine gun were mounted inside the fuselage at the cabin windows, but this load proved far too heavy, and even more lightly armed H-19 gunships proved underpowered. Some Piasecki H-21 helicopters were armed with fixed, forward-firing rockets and machine guns and a few even had racks for bombs, but the H-21 lacked the maneuverability and performance needed for offensive action. Most H-21s in service were eventually fitted with a single door-mounted 12.7 mm machine gun or an MG151/20 20-mm cannon as defensive armament.

The Sikorsky H-34 was also modified into a gunship by the French Navy: standard armament comprised an MG 151 20-mm cannon firing from the cabin door, two 12.7-mm machine guns firing from the cabin windows to port, plus racks for 37 mm or 68 mm rockets. While the CH-34 was effective in the ground attack role, official evaluations at the time indicated that the CH-21 was more likely to survive multiple hits by ground fire than was the CH-34; this was assumed to be a consequence of the location and construction of the CH-34's fuel tanks. Nevertheless, by the close of the Algerian War, attack helicopters such as the CH-34 were being used in synchronized operations with troop-carrying CH-21 helicopters in large-scale counterinsurgency operations.

The United States Navy and the United Kingdom began modifying existing helicopters as anti-submarine weapons (ASW) platforms, carrying depth bombs and Magnetic Anomaly Detector gear. After learning of French Army experiments, there was a movement within the U.S. Army to arm helicopters. Under the leadership of Colonel Jay Vanderpool, the U.S. Army modified Sikorsky and other larger helicopters with fixed and flexible-mount machine guns, rockets, and cannon. While Col. Vanderpool was ridiculed by some in the Army, others saw his efforts as a great aid to ground troops. At the time, the Army leadership felt that the U.S. Air Force was not doing enough to support ground forces, and due to the Key West Agreement, the Army could not field its own ground attack fixed-wing aircraft.

With the increasing use of the helicopter for infantry transport, the U.S. Army saw a need for specialized helicopters to be used as aerial artillery to provide fire suppression and ground support close to the battle. The first United States use of the armed helicopter in large-scale combat operations was during the Vietnam War. First the U.S. Army modified UH-1B 'Huey' helicopters, mounting machine guns and Folding Fin Aerial Rockets (FFAR) on struts parallel with the fuselage. Eventually, the U.S. Army would upgrade the engine and rotor to the UH-1C model, and again to the UH-1M model, to overcome power issues as more and more armament was added to the helicopters. But this was not fully satisfactory, so the AH-1 helicopter was developed.