One Powerful Helicopter Gunship- the ACH-47A "Guns A-Go-Go"

The weapons loadout of the ACH-47A Chinook gunship

After years of experimentation with armed helicopters, the US Army finally sent armed Bell UH-1B Huey gunships into combat in October 1962 with the rocket/gun armed Hueys acting as escort for Piasecki CH-21 Shawnee transports out of Tan Son Nhut Air Base in Saigon. Despite the growing success of the armed Hueys in the growing conflict in Vietnam, the Army sought a helicopter that offered even more firepower to replace the Huey gunships. Initial evaluations began in 1964 and even despite the selection of the Bell AH-1 Cobra (the world's first dedicated helicopter gunship design) in 1966, the general staff wanted something with even more firepower than the Cobra gunship as it was felt to only be an interim design pending what the Army felt was the ultimate gunship, the Lockheed AH-56 Cheyenne. While the Army pushed for a large gunship based on experiences in Vietnam, it found itself running into opposition from the USAF which felt its traditional domain of fixed wing close-air support being infringed upon by more capable helicopter gunships. Regardless, combat experience proved to be a powerful argument and the existing Hueys were felt in certain situations lacking in firepower. With the Army due to deploy the Boeing Vertol CH-47 Chinook transport helicopter to Southeast Asia in November 1965, Boeing Vertol submitted a formal proposal to the Army to modify eleven Chinooks into heavy gunships and on 2 July 1965 the first test Chinook was diverted from the production line in Philadelphia for conversion into the prototype ACH-47A. 

The heavy lift capability offered by the twin turbine-powered Chinook allowed for many choices of possible armament systems, weapons loads, and self-protection. No concept was considered too outlandish as even manned turrets and stub wings for mounting weapons were considered. The eventual weapons fit of the ACH-47A became the XM5 40mm grenade launcher in a turret in the nose fed by a flexible belt that ran through the cockpit to the forward cabin where a container holding 500 rounds was located; a 30-inch stub wing on each side of the forward sponsons that at the end mounted an M24A1 20mm cannon, each fed by an 800-round container in the middle cabin; under each stub wing was a pylon that could mount either a 19-round 2.75-inch rocket launcher or a pod-mounted 7.62mm rotary Minigun. In addition to these permanently mounted systems, there were five crew-operated 50-caliber gun stations- forward right side, forward left side, right and left waist, and cargo ramp. The waist and forward stations had enlarged openings to allow a wider field of fire and the top half of the cargo ramp was removed to expand the rearward field of fire. Each 50-caliber gun had its own 1,000 round supply. With the five gunner stations, the ACH-47A would be the only helicopter gunship to fly into combat with a full 360-degree field of fire. 

Two ACH-47As during the flight test program. Note the gloss paint scheme.

Despite the removal of items not needed for the gunship mission (items like the troop seats, cargo handling gear, even soundproofing), over 2,500 lbs went back into the ACH-47A for armor plating for the crew, rotor pylons, and vital systems. The standard Lycoming T55 turboshaft engines were uprated to 2,850 hp each compared to 2,200 hp for the standard CH-47A transport. This meant that a fully-loaded ACH-47A had the same performance as a operationally-loaded CH-47A. The first ACH-47A made its maiden flight at the Boeing Vertol plant in Philadelphia on 6 November 1965, only four months after the work began! After flight testing, the first ACH-47A was delivered to the Army for weapons trials at Aberdeen Proving Ground in Maryland and then to Fort Benning, Georgia for operational training in March 1966. At Fort Benning, the 53rd Aviation Detachment, Field Evaluation (Provisional) was formed for the training and operation of the ACH-47A and in April 1966 three more ACH-47As arrived, but due to budgetary constraints, only four ACH-47As could be built and delivered. The first one, 64-13145, was initially named "Crazy 8" but was renamed "Cost of Living". 64-12149 became "Easy Money", 64-13151 was named "Stump Jumper" and the last one, 64-13154, was named "Birth Control". The last three shipped out to Vietnam in May 1966 while "Cost of Living" remained at Edwards AFB for more testing. 

"Easy Money" resting between missions at An Khe

The six-month period of operational testing would be split between Vung Tau in the southern coast one hour downriver from Saigon and at An Khe in the centeral highlands of South Vietnam. At Vung Tau the ACH-47As would operate not just with American units fighting the Viet Cong but also the Royal Australian Task Force. At An Khe, the ACH-47As operated with the 1st Cavalry Division. At both locations the 53rd Aviation Detachment remained the operator and acquired the nickname "Guns A-Go-Go" as a result of the heavy firepower of the Chinook gunships. Troops in contact with enemy forces favored the ACH-47As for their firepower and 360-degree field of fire. On 5 August 1966, "Stump Jumper" was destroyed in a freak accident at Vung Tau when it collided while taxiing with a transport CH-47A. The ACH-47A that was still at Edwards AFB "Cost of Living" conducting advanced testing was then prepared for deployment to replace the destroyed "Stump Jumper". One of the missions assigned exclusively to the ACH-47As was to go into an area that had just been carpet bombed by a B-52 Arc Light strike and finish off any enemy positions that survived the bombing. It was considered heavily armed enough and heavily protected enough to be able to finish off the job left by an Arc Light strike!

At the end of the test period in December 1966, "Cost of Living" arrived in Vietnam and the 53rd was redesignated the 1st Aviation Detachment (Provisional) attached to the 1st Cavalry Division at An Khe. Enemy forces became reluctant to fire upon any Chinook after a while because at a distance, the ACH-47A was hard to distinguish from a standard CH-47A transport Chinook. On 5 May 1967 while on an attack run, a retention pin on the stub wing of "Cost of Living" came loose and allowed the gun to elevate and fire into the forward rotors, causing the gunship to crash with the loss of all onboard. The two remaining ACH-47As, "Easy Money" and "Birth Control", however, kept flying as the need for their firepower was highly desired by troops in contact. The end of the Chinook gunship program came during the 1968 Tet Offensive at the Battle of Hue. On 22 February 1968, "Birth Control" was forced down due to multiple hits after an attack run in low ceiling conditions. Autorotating into a rice paddy near the walls of the Citadel in the ancient city of Hue, the crew started taking heavy fire from the Citadel area. "Easy Money" made several attempts to land and rescue the crew of "Birth Control", but the ground fire was too intense. "Easy Money" finally landed, but overshot and found itself between the Citadel and "Birth Control". Two UH-1 Huey gunships unleashed 76 2.75-inch rockets into the source of the enemy fire, allowing "Easy Money" to struggle airborne with the crew from "Birth Control". Before the downed ACH-47A could be recovered, it was destroyed by enemy mortars. Since the tactics called for the ACH-47As to operate in pairs, "Easy Money" never flew into combat again as no Chinooks were available for conversion as every one was needed for transport duties in Vietnam. With the number of Bell AH-1 Cobra gunships increasing in Vietnam, "Easy Money" sat out the rest of the war as a maintenance trainer at Vung Tau.

The logo of "Guns A-Go-Go

"Easy Money" ended up in the boneyard at Savannah Army Depot. Boeing had evaluated the airframe for possible conversion to the prototype CH-47D, but it was found to be too corroded to be of any use. It was moved to Fort Eustis where it was used as a sheet metal trainer before it was moved to the base scrapyard. It's historical identity was discovered in 1997 when the "Easy Money" name was uncovered under layers of paint. The aircraft was duly restored and is now on display at Redstone Arsenal, in Alabama. In 2006, the 160th Special Operations Aviation Regiment "Nightstalkers" at Fort Campbell, Kentucky, set up a new battalion at Fort Lewis, Washington, to serve special operations units based on the West Coast for operations in the Pacific. Equipped with the advanced MH-47G Chinook, the unit approached the veterans of the 53rd "Guns A-Go-Go" for permission to resurrect the unit designation, patch, and "Guns A-Go-Go" call sign- which of course was agreed to with enthusiasm!

I highly recommend you visit a tribute website to the ACH-47A and "Guns A-Go-Go"!

Source: Helicopter Gunships: Deadly Combat Weapon Systems by Wayne Mutza. Specialty Press, 2010, p41-55.