Air Cushioned Vehicle
air cushioned vehicle (ACV) was developed by Bell
Aerosystems in the late 1950s. The ability to move
quickly over land and water using a cushion of air
left other vehicles and watercraft behind, and
caught the attention of the Army and Navy.
first developed the US Navy's Patrol Air Cushion
Vehicle (PACV “Swift Boat”) based on a modified
British design SR-N5. The Navy's PACV first arrived
in Vietnam as a unit in 1966.
Army worked with Bell to develop it's own version of
the ACV in February 1968. It was wider, longer and
carried more weapons than the Navy PACV. It also
had stronger side decks and the front door of the
cabin was widened to accommodate soldiers with gear.
a turbine-powered, turbo shaft GE engine, a Hamilton
3-bladed, variable pitch, fully reversible
propeller, and a centrifugal, 7 foot diameter,
12-bladed blower fan.
Army ACV unit deployed to Vietnam in May 1968, with
three ACVs - hull numbers 901, 902, and 903. The
unit was initially stationed at Dong Tam, and later
relocated to Ben Luc, under the control of the 9th
Patch of the
9th Infantry Division
901 and 902 were in assault configurations with a
full weapons load. ACV 903, although identical to
her sisters, was a transport variant and armed with
only window mounted M-60 machineguns. The .50
caliber machine guns and 40mm grenade launcher were
not installed, to save room for carrying troops in
ACV-903 pulling guard duty on the Plain
of Reeds, 1969.
ACV unit conducted a variety of different missions:
training, supply, patrol, reconnaissance, assault
and ambush. They were also a blocking force in
execution of these missions, the ACV unit developed
tactics. They found working in pairs to be
preferable to operating alone. This allowed for the
ACVs to offer support in case one got into trouble.
using two or three ACVs together, especially in land
operations, an experienced crewmember flying in a
helicopter to coordinate movements was preferred.
operations began, troops chose to ride on the
outside hull rather than inside the cramped cabin.
They could move around easier, disembark faster, and
add their personal weapons to the ACVs firepower in
led to the full assault configuration of ACV 903, to
match ACV 901 and 902.
Because the ACV unit was a one-of-a-kind unit, they
faced unique difficulties.
first was training. There were only 24 men assigned
to the unit. They had to train their own
replacements for operating and maintaining the ACV.
This required that one craft was kept aside for 14
days during each month.
second was unexpected maintenance and repair caused
by battle or accidents. There was no in-country
support organization for maintenance or replacement
parts until late 1969. This support had to come
from the states.
months in 1969, ACV 901 was unavailable because of
an accident which severely damaged the rear of the
ACV. In April 1969, only one serviceable engine was
available for the ACVs; the other five were en route
to or from servicing in the states. Only during
June 1968 were all three in operation.
Unofficial patch and logo
late 1969, the ACV unit was assigned to the 20th
Transportation Company, 34th General Support Group
for maintenance and logistical support, and the
Marine Corps agreed to service the engines at Phu
1970, control of the ACV unit was assigned to the
3rd Brigade, 9th Division, as the rest of the 9th
Division redeployed to the US. The ACV unit adopted
the unofficial designation as the 39th Cavalry
One of the SK-5s at Dong Tam, January
ACV unit stayed in Vietnam until the fall of 1970.
ACV #901 was destroyed in January 1970, and ACV #902
was destroyed in August 1970. ACV 903 was returned
to the states and is on display at the
Above, the SK-5
refueling. Note the deflated rubber
skirts. Dong Tam, 1969.
Above, an SK-5 arriving with fully
inflated skirts. Dong Tam, Vietnam,
* * *
THE PLAIN OF REEDS 1968
conducting a combat operation in July 1968 in
support of a South Vietnamese CIDG (Civilian
Irregular Defense Force) unit and US infantry
advisors, the Army SK5s were engaged in a 7-hour
continuous fight with enemy forces.
902 and 903 were assigned as a blocking force for a
large scale operation being conducted by 3rd
Brigade, 9th Infantry Division, in an area
surrounded by canals on three sides.
the reconnaissance sweep, the SK5 boats inspected
over 60 houses along the waterline and discovered
over 25 bunkers within the area.
destroying the bunkers with their supporting
infantry, the two hovercraft came under enemy fire.
Both craft returned fire, but were unable to press
the attack since the CIDG forces were unwilling to
dismount into a potential ambush.
disengaging, both ACVs repositioned to another area
and were once again taken under fire. Both vessels
returned fire and when the infantry inspected the
area they discovered several killed enemy soldiers.
5pm, the ACVs were returning to their temporary base
at My Phouc Tay when they spotted a group of enemy
soldiers in the open. The Viet Cong (VC) were
caught by surprise by the hovercraft and when
engaged, they were unable to fade into the foliage
boat crews called for infantry and air support, but
were unable to get either due to the onset of
nightfall. Both ACV 902 and 903 fought the enemy
soldiers, who were in open bunkers until their
ammunition supply was exhausted. Some soldiers and
crewman of the boats were wounded in the firefight
and both boats received battle damage from automatic
weapons fire and mortars.
seven hours of repeated engagements, the two SK5
hovercraft retired to their base to tend to the
wounded and effect repairs.