A door gunner is a crewman tasked with firing and maintaining manually directed armament aboard a military helicopter.
The concept of the door gunner originated during the Vietnam War, when helicopters were first used in combat in large numbers.
The monkey harness allowed a door gunner great movement, including to lean outward on the helicopter skids, to get a better firing angle.
According to popular legend, the door gunner on a Vietnam era Huey gunship had a life span of 5 minutes.
The UH-1 (still in use by the U.S. Marine Corps, as the UH-1Y) is still manned as it was in the Vietnam War, with the gunner firing from the open cabin door.
They normally undergo a specified training period (normally referred to as a "progression") and then assume part-time or, in some cases dependent on the needs of the companies and the battalion as a whole, full-time flying duties.
Besides manning the machine gun, they are responsible for weight and balance, take-off and landing data, preflight, radios, defensive systems, scanning, hoisting, deploying ropes and must be proficient in NVG operations.
Most door gunners use some sort of machine gun such as the M60 or the M60D (a modification of the basic M60 for aircraft), M240, M2HB, or more recently, the General Electric M134 minigun.