Boeing CH-47 Chinook ACH-47A

The ACH-47A was the US Army's most ambitious attempt to turn its heavy-lift helicopter into a fire-support platform. Before it received that official designation it was called the Armed/Armored CH-47A (sometimes shortened to A/ACH-47A); the Army then classed it as an Attack Cargo Helicopter, and its crews unofficially nicknamed it "Guns A Go-Go", a name that ended up identifying the unit itself.

Boeing Vertol prepared four examples in late 1965 from CH-47A airframes. Sources differ on the nuance: some describe four Chinooks specially built for the role, others four converted CH-47As. The work added armour for the crew and for some critical components, fitted improved engines and gave the aircraft a weapons fit never before seen on a transport helicopter. The first, serial 64-13145, served as the prototype and stayed at Edwards Air Force Base for flight and weapons testing; the other three (64-13149, 64-13151 and 64-13154) were earmarked for field evaluation.

The armament was layered. Five gun positions - four at the windows, using the XM32 subsystem, and one on the rear ramp, using the XM33 - carried 7.62 mm M60D or 12.7 mm M2HB machine guns. Two 20 mm M24A1 cannon were fixed to fire forward (XM34 subsystem). On the sides hung two XM159B/XM159C 19-tube launchers for 70 mm rockets or, instead, two M18/M18A1 7.62 mm minigun pods. In the nose, an M5 (XM5) turret held an M75 40 mm automatic grenade launcher, the same system more often seen on the UH-1. The crew numbered eight.

On 18 January 1966 Lieutenant Colonel William J. Tedesco took command at Fort Benning, Georgia, of the evaluation detachment formed for the programme. On 19 April the unit was renamed the 53rd Aviation Detachment Field Evaluation (Provisional) and ordered to South Vietnam on six months of temporary duty: three at Vung Tau and three at An Khe. According to the Army Aviation Museum, the ACH-47As destroyed every target they were assigned during that evaluation.

The campaign soon claimed aircraft. On 4 July 1966, 64-13151 lost an engine during a gun run and had to land in a field full of tree stumps, badly damaging its underside; from then on it was known as "Stump Jumper". Thirty days later, in August, it was wrecked - broken in two - in a taxiing collision with another Chinook at Vung Tau airfield. That loss halted the prototype's trials at Edwards, and it travelled to South-East Asia to join its two sisters. In early December 1966 the detachment was attached to the 228th Assault Support Helicopter Battalion of the 1st Cavalry Division (Airmobile) and became the 1st Aviation Detachment (Provisional); the prototype, later named "Co$t of Living", arrived a few days afterwards.

On 5 May 1967, near Bong Son, "Co$t of Living" had just completed a run alongside "Easy Money" when a forward mounting pin on one of its 20 mm cannon vibrated loose: the weapon swung upwards, fired into the forward rotor, the blades separated and the helicopter tumbled to the ground. All eight crew were killed. On 22 February 1968, in the push to retake Hue during the Tet Offensive, "Birth Control" was hit while pulling out of a run and autorotated into dry rice paddies about 600 metres north-west of the Citadel. "Easy Money" placed itself between the downed aircraft and the enemy, covered the rescue of the crew with its fire and, despite the extra weight and several hits that wounded some of the men in the rear cabin, reached Camp Evans. Before a recovery could be attempted, North Vietnamese mortars destroyed "Birth Control" on the ground.

With a single ACH-47A still flying, which the Army would not allow to operate alone, and with transport helicopters badly needed, the programme was cancelled and the unit disbanded. The aircraft had proved effective in the assault role, but they were costly to maintain and suffered several accidents; moreover, the arrival of the AH-1G Cobra in August 1967 offered an escort that was faster, could loiter longer over the target and was a far smaller target itself. The French Wikipedia adds that the large, unwieldy ACH-47s proved easy targets. No further conversions were made.

"Easy Money" (64-13149) stayed at Vung Tau as a maintenance training airframe at Boeing's in-country facility until the end of the war. Back in the United States it served at Fort Eustis, Virginia, which it reached in 1995 as a trainer for the Transportation School's sheet-metal course. Restored in the late 1990s, it went on permanent display at Redstone Arsenal, Alabama, on 1 May 2000. A Rock Island Arsenal team rebuilt its demilitarised armament for the occasion: five 12.7 mm machine guns with spade grips, two 19-shot rocket launchers and what they believe was the last remaining M5 turret, found at Yuma. Since that reunion, the "Guns A Go-Go" veterans have met every two years.