In 1968, the U.S. Army created the Air Cushion Vehicle Unit in Vietnam. For the next two years, the ground combat branch’s hovercraft would chase guerrillas around the Mekong River Delta.

The ACV Unit was experimental and received three newly-developed craft. Bell Aerosystems derived the SK-5 design from the British Saunders-Roe SR.N5, the first production hovercraft in the world.

Bell had already license-produced a number of SR.N5s for the U.S. Navy. The sailing branch started using these hovercraft in Vietnam two years before the land service stood up its unit.

Navy hovercraft skimming up and down the Mekong might seem more logical than Army units riding on the river. However, the ground combat branch has a long history of amphibious operations and of partnering with their seafaring brothers in arms.

The two services had also already established a shared command—the Mobile Riverine Force—to tackle insurgents in the Mekong region. The Army was impressed by the sailing branch’s Patrol Air Cushion Vehicles after seeing them in action.

A U.S. Navy Patrol Air Cushion Vehicle exits the USS Gunston Hall in Vietnam. Navy photo

The vehicles used their cushion of air to ride across the rivers and canals and flooded rice paddies and muddy lowlands. The hovercrafts were also fast and could move from the water to land at relatively high speeds.

In contrast, Army armored formations regularly got bogged down in the Mekong. The ground combat branch relied heavily on helicopters and Navy boats to schlep troops around.

The air cushion vehicles offered a potential solution. The vehicles were like combinations of tanks, helicopters and amphibious landing craft.

The connection to helicopters and the new “air cavalry” was most obvious. Bell made the Army’s Huey helicopters in addition to the SK-5s.

The Army planned to arm each of these craft with machine guns—including a rapid-firing Minigun—and automatic grenade launchers. The grenade launchers were originally designed for gunships.

In the end, just one vehicle got the grenade launcher. The Army removed the machine guns from the main cabin of another in order to make more space for troops and cargo.

The ACV Unit—also known as the Air Cushion Vehicle Test Unit, Armor Platoon Air Cushioned and 39th Cavalry Platoon—spent most of its time patrolling the Mekong and participating in attacks on suspected base camps.

The vehicles also inserted commandos into enemy territory and ambushed enemy fighters. The hovercraft had shock value because they were so loud. Guerrillas reportedly called all American hovercraft “monsters.”

But the craft made no sound when their engines were off—and each of them had radar. Able to get into remote areas, the hovercraft could power down and act as sort of impromptu guard posts.

The initial reports on the platoon were positive. The U.S. Army Combat Developments Command quickly recommended buying more hovercraft to form a larger contingent.