2 Photos: The Strange U.S. Navy Hovercraft That Fought in Vietnam – My Comments
[This is the first time that I've come across hovercraft used in combat. I find this fascinating. But as always this is a tribute to the creativity of our race – in this case Americans. Jan]
The big, awkward-looking, air-cushion vehicles surprised by the Vietcong (and the U.S. Navy) by riding over any terrain at 70 mph, knocking over trees and capsizing enemy sampans.
In the November 1967 issue, Popular Mechanics took a ride on the Navy’s strangest vehicle the Patrol Air-Cushion Vehicle (PACV). Based on the Bell Aerosystems SK-5 hovercraft, the PACV served in Vietnam from 1966 to 1970. The idea was these vehicles could ply Vietnam’s rivers, bursting through fallen trees, and attacking enemy boats (armed with twin .50-cal machine guns no less). Ultimately, the PACV proved too costly and too unreliable and were soon relegated to Coast Guard service.
"On the way to the Plain of Reeds,” Mike Vincent said, "the last ACV in the column radioed they thought they had hit a land mine. We didn’t stop we were moving through VC territory.
“Later, we took a look. All we found were some holes in the craft’s skin, aft. Nobody was hurt, and there was no structural damage.
"We’re not sure it was a land mine, but it takes more than that to stop a skimmer at 60 knots.”
That’s right. Sixty knots (about 70 mph) across flooded paddies, mud flats mangrove swamps, saw-grass hummocks. ACVs (air-cushion vehicles) can go where even helicopters can’t land. You’re down on the ground, churning up spray, carrying 10 or 15 Green Berets and Vietnamese irregulars on the sloping deck. You can plop down anywhere—on hard ground, muck, or water-search sampans and grab prisoners hiding in the reeds then lift up and streak away.
That’s what guys who were there say about the U.S. Navy’s odd inland mission to test three Bell SK-5 ACVs, armed with machine guns, in action in Vietnam. Lt. Mike Vincent was executive officer of PACV (Patrol Air Cushion Vehicle) Div. 107. Now a civilian, he works for Bell Aerosystems, builder of the skimmers.
Will hovercraft (as they’re also known) prove to be the weapons that can sweep the guerrillas out of the waterlogged South Vietnam delta?
"I think the feeling among those who participated in the evaluation is that as long as the engine keeps running there isn’t anything you can’t do with the craft,” Mike told PM.
The big, awkward-looking pancakes surprised a lot of people by turning out to be rugged fighting machines. The Vietcong were shocked when the skimmers came crashing through the reeds, destroying their supplies by running over their hidden sampans and capsizing them. The Navy crews were delighted when they knocked over 20-foot trees. Maintenance mechanics were surprised when they came upon field repairs that crewmen had made under combat conditions such as a flattened beer can used as a shim to fix the steering gear.
The three PACVs—called “Pak-Vs" by their crewmen—were originally assembled in England by the SaundersRoe Div. of Westland Aircraft. They were modified and “Americanized” (fitted with standard U.S. components) by Bell, which has the U.S. license to manufacture them.
They were armed with twin .50-cal. machine guns mounted in a turret in the cabin roof, plus two 7.62-mm. machine guns in helicopter-type mounts, firing from the side windows of the cabin. High-resolution radar is standard on the SK-5s. This enabled the ACVs to run without lights at night.
Thirty-nine feet long and 24 feet across the beam, each SK-5 is powered by a single 1150-hp General Electric gas turbine, burning kerosene jet fuel. The engine drives both a nine-foot-diameter pusher propeller and a seven-foot lift fan. The fan forces air downward into a plenum chamber and then through slots around the periphery of the hull to create and trap a bubble of compressed air under the craft’s flat bottom. That’s what an air-cushion vehicle rides on.
In the SK-5, the air slots are extended by flexible rubber "skirts” that run all around the craft. The increased height of the air cushion raises the SK-5 about four feet off the ground, plus a few inches of daylight below the skirts. The skirts allow the skimmer to clear obstacles five or six feet high, and they smooth out the ride over waves.
Steering is by means of twin rudders in the pusher prop’s slipstream, aided by skirt-lifting rods in the hull. These serve somewhat like a plane’s ailerons, enabling the craft to bank for tight turns.
The 40 officers and men of PACV Div. 107, under the command of Lt. Kenneth H. Luenser, took training at Bell’s skimmer base in Buffalo on Lake Erie, and at the Navy’s Fleet Amphibious Base at Coronado Beach, Calif., before going to Vietnam with their craft in May last year.
On Nov. 20, a Sunday, the three skimmers began "Operation Quai Vat” named after the Vietnamese term for "monster.” Grinning mouths, full of shark’s teeth, had been painted on the bows of the ACVs.
The Pak-Vs set out each day for targets assigned on a map by a Special Forces intelligence officer.
One or two officers and four men typically made up the crew of a Pak-V. There was space in the cabin for four more—"We tried to reserve that space for prisoners," said Vincent. Outriders were also carried on top of the plenum chamber—Special Forces and Vietnamese soldiers picked up at Moc Hoa or along the way.
The three Pak-Vs would work together as a fleet. Most of the time they also had helicopters working with them, scouting ahead and directing the skimmer’s toward suspicious areas. Sometimes the craft would be engulfed in vegetation taller than their 16-foot radar masts, and they would be dependent on the copters to track them in the elephant grass. They had to go around wooded areas, but the mud sailor’s discovered they could drive right through groves of saplings a couple of inches in diameter and 20 feet tall.
"It was swamp and I don’t think those trees were really solidly rooted,” says Vincent. "Our main concern, when we were going through trees, was to protect our eyes. There were branches flying all around, and the windows were open for the machine gunners. It got pretty wild sometimes, plowing through those trees at 45 knots."
The Pak-Vs were also used as battering rams to knock over the huts. The most dramatic action came in an attack on a fortified village on Nov. 22. The Pak-Vs were working as part of a combined force including swamp boats and the unarmed troop-carrying helicopters called "slicks." This is Lt. Luenser’s report:
"We were making a sweep and we came into one area that had a lot of houses and bunkers in it. We put off the Vietnamese troops on board. They found a few rifles and hand grenades, but the area was very heavily booby-trapped. I called the troops back on board because I was afraid we were going to get someone hurt pretty seriously. We left the area and I called an air strike in on it.
"About that time one of the helos reported sighting a large concentration of sampans. We asked for a vector and proceeded to that area at high speed.
"As we proceeded, the slicks were bringing in ground troops and landing them. We caught some of the Vietcong running across an open field toward their village. The ground was wet, muddy, maybe ankle-deep in water. We did some shooting up of people right there in the field, but a few got to the village.
"The village was surrounded by sort of a wall and we were receiving some fire from it. So we turned and the Pak-Vs made two high-speed runs, shooting into the village with our twin-.50s.
"We fired approximately 2000 rounds per craft that day, the majority of it in this one engagement. We were getting fire back from a window in this fortification—my gunner estimated it to be .30cal. machine-gun fire. He fired into the blast of the muzzle flash and silenced it.
"THERE WERE BRANCHES FLYING ALL AROUND, AND THE WINDOWS WERE OPEN FOR THE MACHINE GUNNERS. IT GOT PRETTY WILD SOMETIMES, PLOWING THROUGH THOSE TREES AT 45 KNOTS."
"A Special Forces captain in the air boats, closer in, said our gunner apparently split this machine gun right down the middle. He told me that what caught his eye was the steel flying around and the man shooting it being upended."
During Operation Quai Vat, the Pak-Vs were officially credited with 23 Vietcong killed in action. They destroyed 71 Sampans, 71 land structures and a printing press used for Communist propaganda. A total of 194 bunkers were discovered and checked out. The Pak-Vs captured 11 Vietcong soldiers, a quantity of arms and ammunition, six outboard motors and 60 pounds of documents.
Amazingly, no one in the Pak-V unit was even injured during the entire period in Vietnam. This was probably due to the high speed and maneuverability of the cushioncraft, which made them elusive targets despite their size.
Of course the ACVs were hit by enemy fire many times, and plenty of holes in their plenum chambers and rubber skirts had to be patched. Although an air-cushion vehicle rides on compressed air, it’s pretty hard to get a "flat." The powerful lift fan keeps pumping air into the cushion to make up for even major leaks. The Bell skimmers can still go with a five-foot hole in the plenum chamber.
The Plain of Reeds operation showed that emergency repairs could be made under combat conditions. Mike Vincent told of the time the steering controls on the craft he was commanding failed.
"We got hung up in some trees,” he said. "I rigged a couple of ropes to the rudders. I wanted the turret gunner to do the steering, but he said, ‘Hell, Mr. Vincent, I gotta operate the gun.’ So I pulled on the ropes myself. The pilot told me when to give her right or left rudder.
“I still have the blisters on my hands but we were able to go along at about 30 knots and get back to base.”
What does the trial of the skimmers in Vietnam prove?
Hovering just off the ground—"flying" without really flying—air-cushion vehicles are in many ways somewhere between aircraft and land or water craft.
original caption dong, tam, so vietnam the navys new patrol air cushion vehicle pacv is demonstrated, capable of speeds of 40 50 knots, the craft will be used for riverine assault missions, including blocking and interdiction patrols, search and rescue, high speed troop transportation and logistic support
Able to carry fuel for up to eight hours of operation, an ACV can stay on station longer than a helicopter. Maintenance is considerably simpler than for an aircraft.
Like aircraft, the ACVs can travel at high speed over terrain impassable to land or water craft, as well as over dry land and water. They are limited to reasonably flat terrain, however, since the air cushion provides no traction.
PACVs could conceivably become the "tanks" of the war in Vietnam-floating fortresses—able to maneuver at high speed over terrain where no conventional armored vehicle can travel. Unaware of the capabilities of the cushion craft, the Vietcong didn’t know how to cope with them. Whether they have learned from their setbacks remains to be seen.
The Navy’s future plans for the Pak-Vs are still secret. The three craft of Div. 107 were brought back and were being refurbished and modified somewhat at Coronado Beach. It seems likely that they will have a future in Vietnam.
Another indication may be that Bell Aerosystems has tooled up at its Buffalo plant for production of 65 skimmers. The first 20—larger and with more armament—were scheduled to roll off the line in October, and the monsoon rains will be over again in Vietnam this month.