The majority of Viet Cong and NVA attacks against bases took place at night and the Air Force responded by converting the Second World War vintage transport planes into flying gun platforms. The AC-47s were armed with three 7.62 miniguns, each capable of firing up to 6,000 rounds per minute, in one side of the fuselage; several tons of ammunition were also loaded on board. The planes could circle a base when it was under attack, illuminating the target area with 2-million candlepower flares. It would stay overhead until the base’s own helicopters were in the air and able to take over. They were known as Spooky, but the GIs christened it Puff the Magic Dragon after a well-known song because the thousands of tracer bullets made it look like the plane was breathing fire.
The AC-119 Shadow and AC-119 Stinger were introduced at a later date. The Stinger was also armed with two 20mm multi-barrel guns capable of firing up to 2,500 high explosive incendiary rounds per minute while a 2-billion candlepower searchlight lit up targets.
The need for fighter planes to be fast and highly maneuverable seriously restricts the weight and bulk of the guns and ammunition that can be fitted into them; this limits their ability to strafe ground targets. A cargo plane, with machine guns in the cargo bay firing sideways, is not subject to these restrictions and can place much heavier fire on ground targets.
The United States began giving serious consideration to this idea in 1963. In December 1964, combat tests began in Vietnam of an aircraft initially designated the FC-47: an old C-47 cargo plane, with six 7.62-mm miniguns each capable of firing either 3,000 or 6,000 rounds per minute, all pointed to the same side of the aircraft. The tests were successful, and more C-47s were converted in the following months, with varying armaments. Three miniguns per plane eventually became standard. The plane was redesignated the AC-47 late in 1965. It was officially called the “Spooky,” unofficially “Puff the Magic Dragon.” The U.S. Air Force (USAF) stopped operating AC-47s in Southeast Asia toward the end of 1969; most of the aircraft were turned over to the Vietnamese Air Force and the Royal Laotian Air Force. The AC-47 had had an impact on the war far out of proportion to its numbers—only 53 were built—and very low cost.
Toward the end of 1966, modified AC-47s with added armor and fire extinguishers were being sent to Nakhon Phanom in Thailand, to be used for operations in Laos, where the danger of ground fire was too great for the unarmored AC-47s used for missions in South Vietnam.
The AC-130 Spectre was a larger and much more modern aircraft. It carried four 7.62-mm miniguns, and also four 20-mm Vulcan cannons. The Vulcan used the same basic Gatling-gun design as the minigun: six barrels rotating at high speed around a common axis. Early Vulcans could fire 2,500 rounds (usually high-explosive incendiary, sometimes armor-piercing incendiary) per minute. Later models fired up to 6,000 rounds per minute. The AC-130 also carried more equipment than the AC-47 for detecting targets at night: a side-looking radar, an infrared device that could detect the engines of trucks by their heat, and a starlight scope that could amplify images in dim light. Initial combat tests from September to December 1967 were highly successful, but there was resistance to the AC-130 design from people who felt that the Air Force needed its limited number of C-130 aircraft for transport purposes, and could not afford to convert any significant number of them to gunships. Arguments over this issue, and problems with the infrared gear and other equipment, delayed the program; in late 1968 and early 1969 only four were in action, based at Ubon in Thailand, and mainly devoted to hunting trucks on the Ho Chi Minh Trail.
Some AC-130 aircraft were given heavier weapons, both to make their fire more destructive and to enable them to fire from a greater distance and thus reduce their exposure to anti-aircraft fire. The Surprise Package variant of the AC-130A, carrying two 40-mm Bofors cannon originally designed as anti-aircraft guns, plus two 20-mm guns, underwent its first combat trial in December 1969; the 40-mm cannon became standard equipment for the AC-130 during 1970. The Pave Aegis variant of the AC-130E, introduced around the beginning of 1972, had a 105-mm cannon as well as one 40-mm and two smaller guns.
The AC-130 also came to be equipped with a laser target designator, to guide a smart bomb (see bombs) to its target. The first combat use of this system was on February 1, 1971; the bomb was dropped by an F-4 Phantom.
The AC-119, based on the old C-119 “Flying Boxcar” transport plane, was slower than the AC-130 and had less armor and much less powerful guns, but it was cheaper; it eventually replaced the AC-47 as the USAF gunship for use inside South Vietnam, and was also used to a significant extent in Cambodia and Laos. The AC-119G Shadow, equipped with four 7.62-mm miniguns, began to arrive in Vietnam in the last week of 1968, and began combat trials early in 1969. The AC-119K Stinger, with four miniguns and two 20-mm cannon, began to arrive in South Vietnam in November 1969 and began combat trials the same month.
A Cheap and Simple Concept
The fixed wing gunship was a great developmental and operational success. A few dedicated, innovative individuals brought forth a new concept quickly and cheaply that fit the war that was being fought in Vietnam. The basic gunship concept is quite simple: an aircraft flying in a level turn around a point on the ground (as if tethered to a pylon, hence called a “pylon turn”) can deliver fairly accurate firepower from guns firing perpendicular to the line of flight. This concept was first proposed in 1926 and demonstrated the next year. A number of other airmen later advanced the idea, but the Army Air Forces/US Air Force did not pick up on it until the early 1960s. The idea reached Capt. John Simmons at Wright-Patterson AFB, Ohio, through an indirect route. After overcoming numerous rebuffs, he pushed through a modest test program in mid 1963 that demonstrated that a pilot could track a target while in a pylon turn. The breakthrough came in August 1964 when a C-131 armed with a 7.62 mm Gattling gun achieved better than expected accuracy in firing tests over the Gulf of Mexico. The next month, three Gattling guns were mounted aboard a C-47 and also successfully tested. Capt. Ronald Terry forcefully articulated a concept of C-47s delivering accurate and massive firepower to hamlets under attack. Things moved ahead rather rapidly, for on November 2, 1964 Terry helped brief the concept to the Air Force Chief of Staff Curtis LeMay, who ordered that the C-47 be tested in Vietnam.
Opposition to the Gunship Concept
There was opposition to the concept. Gen. Walter Sweeney, commander of Tactical Air Command, had two seemingly contrary objections: could the aircraft survive, and if so, would it undermine the Air Force’s position in the battle with the Army over armed helicopters? In addition, he did not see how the gunship would work in other conflicts, specifically one in Europe. Therefore, success in Vietnam might saddle the command with a number of aircraft that would prove useless and vulnerable where it really counted, in Europe. Certainly, the idea of using obsolete transports to support besieged hamlets at night, at low speeds, and from low altitudes did not appeal to the airmen, who thought primarily in terms of newer aircraft flying ever higher and faster. Nevertheless, the tests went forward.
Gunships Quickly Prove Their Worth
Terry and his team arrived in South Vietnam in December 1964. The gunship quickly demonstrated that it not only worked but was valuable. On its first night mission on 23-24 December, it helped repel a Vietcong attack on an outpost. The gunship concept would be used in two very different roles. The first was to provide heavy firepower to ground forces engaged in combat in South Vietnam. The other was to interdict enemy logistics in Laos. The aircraft’s success continued, but better gunships were coming on-line. On December 1, 1969, US Air Force AC-47s flew their last mission. In November 1966, the C-130 was actually picked as a follow-on aircraft. The four-engined turboprop had much greater flying performance than the ancient “Gooney Bird” and carried much heavier firepower, four 7.62 mm and four 20 mm Gattling guns compared to the AC-47’s three 7.62 mm guns. Nicknamed “Spectre,” it also mounted an array of advanced Sensors.