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Development of the Gunship
The AC-47D
Combat Record
The Douglas AC-47D gunship was developed in the early 1960s for use in anti-insurgency operations, and combined a long-standing aerial manoeuvre – the pylon turn – with the use of sideways firing weapons.
A pylon turn is a manoeuvre in which an aircraft turns around a fixed spot on the ground. It was developed during the air races of the early 1920s as the quickest way to turn around the pylons that marked the ends of the race courses.
It soon occurred to a number of military aviators that if the pylon turn was combined with sideways firing guns, then it would allow highly concentrated gunfire to hit a single fixed target. The first known experiment with the idea came in 1926-27. 1st Lt. Fred Nelson, the supervisor of part of the air training program at Brooks Field, San Antonio, mounted a .30in calibre machine gun on the side of a de Havilland DH-4, and successfully hit a ground target while flying a pylon turn.
The idea next appeared in 1942, when Colonel G.C. MacDonald (then a first lieutenant) suggested using the technique as an anti-submarine weapon, with the advantage that a single aircraft would be able to keep up a constant attack on a surfaced submarine. This idea was not taken up, and neither was his 1945 suggestion to mount a sideways firing bazooka in a liaison aircraft to turn it into an anti-tank weapon. MacDonald submitted the idea for a third time in 1961, this time for use in counterinsurgency operations. Once again his suggestion was not taken up.
From MacDonald the idea passed onto Ralph Flexman of Bell Aerosystems, and from him to Captain John C. Simons, who in 1963 proposed the idea once again. This time the proposal received serious study, and a number of technical objections were raised. Despite this, in June 1963 Simons was finally able to carry out the first tests of the concept, proving that the pylon turn could indeed be used to hit a particular target, or even to track moving vehicles.
The programme then stalled for some time, mostly because of resistance to the idea of live firing tests. During 1964 Simons was replaced by Captain Ronald W. Terry, a former fighter pilot. One of his most important contributions to the development of the gunship was to develop a use for it – to develop isolated villages, hamlets and forts against surprise attacks. The Aeronautical Systems Division’s Limited Warfare Office finally became interested in the scheme, believing that it might be of great use as American became increasingly involved in the conflict in Vietnam.
The gunship was seen as one possible answer to a new problem facing the US military. The Communists had begun to launch night time attacks on isolated hamlets, villages and forts. Because they could pick their targets at will, and the defenders rarely had any advanced warning, many of their targets were overrun before help could reach the scene. Fighter aircraft could reach the area, but were of little use for ground attack at night, as they often couldn’t see their targets, and even when they did find the target, often lost sight of them after a single pass. In contrast the gunship would be able to loiter overhead, concentrating its fire where needed.
In August 1964 the Limited War Office approved firing tests, using the Convair C-131 Samaritan transport aircraft. A C-131 was taken to Eglin Air Force Base, where a new General Electric SUU-11A 7.62mm Minigun pod was installed in the left side of the cargo compartment. Firing tests took place late in 1964, and were a great success. One test saw the aircraft score seventy-five hits on a fifty-foot square target in a one-second burst (100 rounds fired), while a three-second firing run hit nineteen of twenty-five manikins scattered across three-quarters of an acre.
Only now did the C-47 come into the picture. It was chosen because a number of Special Forces units in South Vietnam were already using the aircraft. Three miniguns were mounted in the cargo space of a C-47D, and in September 1964 successful firing tests took place with the new combination of aircraft and gun.
Not everybody was convinced that the C-47 was suitable for the gunship role. It was slow, which made it vulnerable to ground fire or hostile aircraft. By the standards of the mid 1960s it had a slow rate of climb, which caused problems over the Vietnamese mountains. The low wings also caused problems, restricting the sideways view. Despite these problems, in November 1964 General Gurtis E. LeMay, then Air Force Chief of Staff, decided to send a team to Vietnam to modify a C-47 and then carry out combat tests.
The standard AC-47A was armed with three General Electric 7.62mm Miniguns, firing through the open dorr and the fifth and sixth port side windows. Until 1967 these guns were mounted in pods, which took ten minutes to reload. From 1967 these were replaced by General Electric MXU-470/A minigun modules, which were designed for the gunships, and could be easily reloaded.
The guns were aimed and fired remotely by the pilot, using the gun sight from an A-1 Skyraider mounted in the left cockpit window. The guns were serviced in flight by a team of armourers in the cargo compartment, who also had the job of dropping flares. The minigun could fire 6,000 rounds per minute per gun, for a total of 18,000 rounds in a minute, although as the aircraft normally carried around 15,000 rounds that rate of fire was not sustainable. The normal tactic was for short bursts of fire, punctuated by reports from the ground.
At first the gunships were designated as FC-47Ds, for Fighter/ Cargo, but this was not popular with the fighter community, and after a review the designation was changed to AC-47D, for Attack/ Cargo.
In early 1965, after the successful service test of the prototype FC-47D, the Air Force ordered another four gunships. Because of a shortage of the new minigun pods, these aircraft, which were converted at Clark Air Force Base on the Philippines, were armed with eight to ten 0.30in calibre machine guns firing through holes in the fuselage side and door. These were replaced by miniguns when the supply situation improved.
The AC-47D gained a number of nicknames. The most famous is “Puff the Magic Dragon”, which came from the 1963 pop song of the same name, and is said to have been adopted by a Stars and Stripes reporter after he saw the gunship in action at night. From this came “dragonship”, while the 1st Air Command Squadron used the call sign “Puff” for the first of the gunships.
The AC-47D was also known as “spooky”, the call sign adopted by the 4th Air Commando Squadron because they spent most of their time operating at night in camouflaged aircraft.
Captain Terry and the testing team reached Vietnam on 2 December 1964, closely followed by the equipment needed to modify two C-47s. The first test aircraft was ready by 11 December, the second by 15 December, and were allocated to the 1st Air Commando Squadron.
The first combat test came in daylight on 15 December, when Captain Terry cooperated with a forward air controller to attack targets of opportunity. The first night attack was made on 23/24 December, in defence of outposts at Thanh Yend and Trung Hung, in the Mekong River Delta. In the two attacks the gunship fired 9,000 rounds of ammunition, and successfully defeated both attacks. Between 15 and 26 December the AC-47 flew sixteen combat sorties, all of them successful.
During the first half of 1965 the Air Force examined the results of these early tests. It was already clear that the C-47 was too small to be a really effective gunship, and the search for a suitable larger aircraft began, but despite this in July 1965 the Air Force decided to order sixteen more gunships, the first four to be armed with machine guns, the rest with minigun pods as they became available. This soon changed to an order for twenty-six gunships, armed with miniguns.
By the time this order was placed four machine gun armed gunships had already been created using surplus 0.30in guns, and were rushed into combat.
All twenty-six of the gunships ordered in July were completed by 25 October 1965, although many lacked the gun pods. They were to be used by the newly formed 4th Air Commando Squadron, then training at Forbes Air Force Base, Kansas. Training began in August 1965 and ended on 1 November, and the squadron reached Vietnam on 14 November 1965.
At this point the South Vietnamese government was rapidly losing control of the countryside, and the AC-47D gunships were desperately needed. Their entry into combat was delayed by the late arrival of the minigun pods, and for a month the squadron was used as a normal C-47 transport squadron, but by 17 December every aircraft had at least one minigun, and in late December the squadron entered combat.
The 4th Air Commando Squadron rarely operated as a single unit. At the end of 1965 it was split into four detachments, one for each of Vietnam’s military corps areas. By the end of the year one of these detachments had moved into Thailand, and was operating over Laos, attacking the Ho Chi Minh trail. This detachment found operations much more difficult than the tests had suggested. The difficult mountain terrain combined with unexpectedly heavy anti-aircraft fire caused the loss of one of the detachments four aircraft on 24 December.
The 4th Air Commando Squadron was remarkable active in December 1965, taking part in 277 combat missions in two weeks. Most of these were defensive missions in support of South Vietnamese forces defending villages and forts.
During 1966 the range of missions flown by the AC-47Ds expanded to include close air support of ground combat units, convoy escort, forward air control, armed reconnaissance and interdiction. Most of these missions took place at night. American airbases and oil stores were also successfully defended. The gunship did have its limits – the A Shau Special Force camp was overrun in early March when poor weather and low cloud prevented the gunships from operating effectively, and one AC-47D was lost after attempting to fly below the cloud base.
The pylon turn also proved to be effective against moving targets – the gunship would fly in a series of loops along a road believed to be in use by the North Vietnamese, and would then fly a pylon turn around a lorry or other target. Once again the Ho Chi Minh trial would prove to be very dangerous for the gunships. The North Vietnamese had 37mm anti-aircraft guns, perfectly capable of shooting down the AC-47D, and three aircraft were lost over Laos in the first half of 1966. The gunships were withdrawn from the effort against the Ho Chi Minh trail in July 1966.
Towards the end of 1966 a second squadron became to operate the gunship. This was the 606th Air Commando Squadron, based at Nakhon Phanom, Thailand, which would use its AC-47Ds against communist insurgents in Thailand and Laos.
The pattern of operations remained the same during 1967, with the AC-47D being used for village defence in the south, air close supprt in the north and a mix of the two in the central highlands. The number of gunships deployed to Vietnam was increased during 1967 in response to a wave of successful rocket attacks on American bases. A third gunship squadron, the 14th Air Commando Squadron, was created to cope with the increase, becoming operational at the start of 1968.
September 1967 also saw the arrival of the prototype AC-130A, armed with four 20mm cannon and four 7.62mm miniguns. This more powerful gunship would eventually replace the AC-47 in US service, but not until 1969. 1967 also saw the first Vietnamese air force C-47s turned into gunships.
1968 began with the Tet offensive and the siege of Khe Sanh, two body blows to American confidence. The AC-47 gunships played an important role in the military defeat of these North Vietnamese attacks, but could not undo the psychological damage inflicted by the unexpected offensive.
The AC-47 gunship was withdrawn from USAF service during 1969. The two squadrons turned their aircraft over to the Vietnamese and Royal Laotian Air Forces. They were replaced in American service by the AC-130 Spectre and the AC-119 gunship, and flew their final sortie on 30 November 1969. The 4th Air Commando Squadron (by 1969 renamed as the 4th Special Operations Squadron) ended operations with a very impressive record. In four years it had defended 3,926 hamlets, outposts and forts, and could claim that no outpost had been lost while an AC-47 was overhead. During this period 97 million rounds of ammunition and 270,000 flares had been used. Of the 53 AC-47 guns that had been built, 41 had been deployed to Vietnam, and during 5,000 missions only 12 had been lost.
After leaving US service the AC-47 went on to be used by the South Vietnamese, Cambodian, Laotian, Thai and Philippine Air Forces. It was revived in 1984, when the US gave El Salvador four C-47 gunships armed with 0.50in machine guns, and again in 1987, when eight went to Columbia. Despite its age the reliability of the C-47 meant that it was perfectly suited for use by less well equipped air forces, and even in the 1980s there was no shortage of spare parts.