In the early 1960s, Air Force Systems Command began experimenting with side-firing weapons systems for possible use in Vietnam in point defense and night Close Air Support (CAS) roles. In late 1964, the first gunship conversion of a World War II Douglas C-47D was done. The gunship version of the C-47D was initially designated FC-47D (Fighter-Cargo), but was changed to AC (Attack Cargo) primarily because of complaints by traditional fighter pilots. The aircraft had several nicknames: "Spooky", Puff the Magic Dragon", and "Puff".
The AC-47D(S/N 43-48579) was equipped with three SUU-11A 7.62 mm "miniguns" with a 6,000 round per minute rate of fire. The miniguns were mounted in the aft left fuselage, one gun was installed in the aft passenger door area. The other two guns were mounted just forward of the passenger door with the gun barrels pointed out window ports. The AC-47D carried about 16,500 rounds of ammunition on a typical mission.
For night missions, the aircraft carried approximately 48 MK-24 flares. Each flare would last up to three minutes (Mod 3 version) and produced a light of 2 million candlepower. The delivery system was extremely simple, the loadmaster armed and dropped the flare out the cargo door when the pilot signaled by flashing a cargo compartment light.
AC-47 Operations Bulletin #56 - 13 Feb 67 (PACAF)
As employed in Southeast Asia, the flight crew consisted of seven USAF personnel, as well as a Vietnamese observer assigned to aid in the "delta" missions. The aircraft commander (pilot) fired the gun while the copilot performs the normal piloting duties and coordinated the activities of the crew. In the target area the navigator and Vietnamese Air Force observer (8th crewman if assigned) collaborate to accurately pinpoint objectives and coordinate with the ground forces. Two gunners accomplish the preflight, gun loading and in-flight troubleshooting of the SUU-11 guns. The loadmaster arms and manually drops the flares from the rear entrance door upon a light signal from the aircraft commander. A flight mechanic rounds out the crew and is responsible for aircraft systems operation.
Initial attack procedures began with the aircraft in straight and level flight, and the target just outside and forward of the left prop dome. Usual altitude is between 2500-3000 feet above ground level (AGL); however, this could be adjusted to allow for such variables as weather, ground fire and target identification difficulties. As the target passed under the engine cowling, the aircraft was rolled into a level 30° bank turn. When the (gun site) pipper came on target, firing was commenced in bursts of 3-7 seconds, as required. When the pipper moved off the target to the rear, the firing was ceased and a slight turn was made away from the target for repositioning and subsequent firing passes. If the pipper moved off the target to the front, the degree of bank was increased to realign on target. Airspeed during the maneuver was normally 120 knots indicated air speed (KIAS). Each minigun fired at a rate of 6000 rounds per minute. This provided a coverage over an elliptical area approximately 52 yards in diameter, placing a projectile within every 2.4 yards during a 3 second burst.
- The basic missions on which the AC-47 was employed were:
- Defense of ground positions (friendly forts and outposts).
- Escort and patrol.
- Pre-planned strikes against suitable targets.
- Forward air controlling for fighter strikes.
The guns were configured for a 12° declination to allow shallower bank angles and more precise aircraft control.