With two 20mm cannons, a 40mm automatic grenade launcher, five .50-cal. machine guns, and two weapon pods that could carry either 70mm rocket launchers or 7.62mm miniguns, the armored ACH-47A Chinook could fly into the teeth of enemy resistance and fly back out as the only survivor.
The aircraft boasted overlapping fields of fire and 360 degree coverage.
Operating under the call sign "Guns-A-Go-Go," these behemoths were part of an experimental program during Vietnam to create heavy aerial gunships to support ground troops. Four CH-47s were turned into ACH-47As by adding 2,681 pounds of armor and improved engines to each bird.
The first three birds arrived in Vietnam in 1966 where they engaged in six months of operational testing. They were tasked with supporting the U.S. Army's 1st Cavalry Division as well as a Royal Australian Task Force.
The Army Pictorial Service covered an early mission flown in support of the Australians where the attack Chinooks were sent to destroy known enemy positions.
Though the gunships performed well in combat, the Army was hesitant to expand the program because of high maintenance costs. Also, conventional CH-47s were proving extremely valuable as troop transports and for moving cargo.
Of the four ACH-47s created, three were lost in Vietnam. The first collided with a standard CH-47 while taxiing on an airfield. Another had a retention pin shake loose on a 20mm cannon and was brought down when its own gun fired through the forward rotor blades. The third was grounded by enemy fire and then destroyed by an enemy mortar attack after the crew escaped.
Since the gunships were designed to work in pairs, one providing security while the other attacked, the Army ordered the fourth and final helicopter back to the states. It was used as a maintenance trainer by the Army until 1997, when it was restored. It is now on display at Redstone Arsenal, Alabama.
The call sign "Guns-A-Go-Go" was recently passed off to Company A of the Army's new 4th Battalion, 160th Special Operations Aviation Regiment.