Patrol Air Cushion Vehicle
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The Patrol Air Cushion Vehicle (PACV), also known as the Air Cushion Vehicle (ACV) in Army and Coast Guard service, was a
United States Navy The United States Navy (USN) is the maritime service branch of the United States Armed Forces and one of the eight uniformed services of the United States. It is the largest and most powerful navy in the world, with the estimated tonnage ...
and
Army An army (from Old French ''armee'', itself derived from the Latin verb ''armāre'', meaning "to arm", and related to the Latin noun ''arma'', meaning "arms" or "weapons"), ground force or land force is a fighting force that fights primarily on ...
hovercraft A hovercraft, also known as an air-cushion vehicle or ACV, is an amphibious Craft (vehicle), craft capable of travelling over land, water, mud, ice, and other surfaces. Hovercraft use blowers to produce a large volume of air below the hull ...
used as a
patrol boat A patrol boat (also referred to as a patrol craft, patrol ship, or patrol vessel) is a relatively small naval vessel generally designed for coastal defence, border security, or law enforcement. There are many designs for patrol boats, and the ...
in marshy and riverine areas during the
Vietnam War The Vietnam War (also known by #Names, other names) was a conflict in Vietnam, Laos, and Cambodia from 1 November 1955 to the fall of Saigon on 30 April 1975. It was the second of the Indochina Wars and was officially fought between North Vie ...
between 1966 and 1970. Six hovercraft were built, three for the Army and three for the Navy. The military developed the PACV because its lack of
draft Draft, The Draft, or Draught may refer to: Watercraft dimensions * Draft (hull), the distance from waterline to keel of a vessel * Draft (sail), degree of curvature in a sail * Air draft, distance from waterline to the highest point on a vessel ...
meant that it could operate unimpeded in the shallow and reed-choked waters widespread in
South Vietnam South Vietnam, officially the Republic of Vietnam ( vi, Việt Nam Cộng hòa), was a state in Southeast Asia that existed from 1955 to 1975, the period when the southern portion of Vietnam was a member of the Western Bloc during part of th ...
, most notably in the
Mekong Delta The Mekong Delta ( vi, Đồng bằng Sông Cửu Long, lit=Nine Dragon River Delta or simply vi, Đồng Bằng Sông Mê Kông, lit=Mekong River Delta, label=none), also known as the Western Region ( vi, Miền Tây, links=no) or South-weste ...
and
Plain of Reeds Plain of Reeds (in vi, Đồng Tháp Mười) is an inland wetland in Vietnam's Mekong Delta. Most of the wetlands are within Long An Province and Đồng Tháp Province. Physical characteristics Đồng Tháp Mười is a "back swamp" forming ...
. The PACV was also found to be valuable because of its unusually high speed of , faster than other watercraft in the conflict. However, it faced major drawbacks, including its high cost of $1 million (equivalent to 13
Patrol Boat, River Patrol Boat, Riverine, or PBR, is the United States Navy designation for a small rigid- hulled patrol boat used in the Vietnam War from March 1966 until 1975. They were deployed in a force that grew to 250 boats, the most common craft in the ...
s) and unreliability. During the conflict, two of the Army's three hovercraft were destroyed by the
Viet Cong , , war = the Vietnam War , image = FNL Flag.svg , caption = The flag of the Viet Cong, adopted in 1960, is a variation on the flag of North Vietnam. Sometimes the lower stripe was green. , active ...
. The PACVs in Vietnam were considered "unsuccessful" in evaluations and were withdrawn in 1970. Following their service in Vietnam, the Navy PACVs returned to the United States where they were used by the
Coast Guard A coast guard or coastguard is a maritime security organization of a particular country. The term embraces wide range of responsibilities in different countries, from being a heavily armed military force with customs and security duties to ...
, where another sank in an accident.


Development

The PACV was based on the
Bell Aerosystems The Bell Aircraft Corporation was an American aircraft manufacturer, a builder of several types of fighter aircraft for World War II but most famous for the Bell X-1, the first supersonic aircraft, and for the development and production of many i ...
SK-5 hovercraft; a
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version of the British
Saunders-Roe Saunders-Roe Limited, also known as Saro, was a British aero- and marine-engineering company based at Columbine Works, East Cowes, Isle of Wight. History The name was adopted in 1929 after Alliott Verdon Roe (see Avro) and John Lord took a co ...
(later,
British Hovercraft Corporation British Hovercraft Corporation (BHC) was a British hovercraft manufacturer that designed and produced multiple types of vehicles for both commercial and civil purposes. Created with the intention of producing viable commercial hovercraft in March ...
)
SR.N5 The Saunders-Roe SR.N5 (or ''Warden'' class) was a medium-sized hovercraft which first flew in 1964. It has the distinction of being the first production-built hovercraft in the world. A total of 14 SR.N5s were constructed. While Saunders-Roe ...
hovercraft. The SK-5 was adapted for American military use in 1965. Three were purchased by the US Navy for operations in the emerging Vietnam War. Training of PACV crews was performed in the waters off
Coronado, California Coronado (Spanish for "Crowned") is a resort city located in San Diego County, California, United States, across the San Diego Bay from downtown San Diego. It was founded in the 1880s and incorporated in 1890. Its population was 24,697 at the ...
near
San Diego San Diego ( , ; ) is a city on the Pacific Ocean coast of Southern California located immediately adjacent to the Mexico–United States border. With a 2020 population of 1,386,932, it is the List of United States cities by population, eigh ...
. Design of the Army ACVs began in 1966 and was completed


Design

Two different designs were made: one for the Navy and one for the Army. The Navy's hovercraft, called Patrol Air Cushion Vehicles, more closely resembled the civilian SK-5s that they were based on while the Army craft had more extensive modifications. Each hovercraft was long, with a
beam Beam may refer to: Streams of particles or energy *Light beam, or beam of light, a directional projection of light energy **Laser beam *Particle beam, a stream of charged or neutral particles **Charged particle beam, a spatially localized grou ...
of and a height of when floating on its air cushion. It weighed fully loaded. Army and Navy PACVs had a crew of 4—driver, radar operator, and gunners—and could carry up to 12 troops, many of whom rode on the outside of the vehicle. Both designs were powered by a
General Electric General Electric Company (GE) is an American multinational conglomerate founded in 1892, and incorporated in New York state and headquartered in Boston. The company operated in sectors including healthcare, aviation, power, renewable energ ...
7LM100-PJ102
gas turbine A gas turbine, also called a combustion turbine, is a type of continuous flow internal combustion engine. The main parts common to all gas turbine engines form the power-producing part (known as the gas generator or core) and are, in the directi ...
engine. The engine, its 304-
gallon The gallon is a unit of volume in imperial units and United States customary units. Three different versions are in current use: *the imperial gallon (imp gal), defined as , which is or was used in the United Kingdom, Ireland, Canada, Austral ...
(1,150
litre The litre (international spelling) or liter (American English spelling) (SI symbols L and l, other symbol used: ℓ) is a metric unit of volume. It is equal to 1 cubic decimetre (dm3), 1000 cubic centimetres (cm3) or 0.001 cubic metre (m3). ...
) fuel tank, an
auxiliary power unit An auxiliary power unit (APU) is a device on a vehicle that provides energy for functions other than propulsion. They are commonly found on large aircraft and naval ships as well as some large land vehicles. Aircraft APUs generally produce 115&n ...
, and the
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transmission Transmission may refer to: Medicine, science and technology * Power transmission ** Electric power transmission ** Propulsion transmission, technology allowing controlled application of power *** Automatic transmission *** Manual transmission *** ...
were located amidships. The engine powered both the three-blade
variable-pitch propeller Variable-pitch propeller can refer to: *Variable-pitch propeller (marine) *Variable-pitch propeller (aeronautics) In aeronautics, a variable-pitch propeller is a type of propeller (airscrew) with blades that can be rotated around their long a ...
for thrust and the diameter
centrifugal fan A centrifugal fan is a mechanical device for moving air or other gases in a direction at an angle to the incoming fluid. Centrifugal fans often contain a ducted housing to direct outgoing air in a specific direction or across a heat sink; such a ...
for lift. The transmission served to link the engine and lift fan so that the fan could provide lift and thrust. Twin
rudder A rudder is a primary control surface used to steer a ship, boat, submarine, hovercraft, aircraft, or other vehicle that moves through a fluid medium (generally aircraft, air or watercraft, water). On an aircraft the rudder is used primarily to ...
s and
elevator An elevator or lift is a wire rope, cable-assisted, hydraulic cylinder-assisted, or roller-track assisted machine that vertically transports people or freight between floors, levels, or deck (building), decks of a building, watercraft, ...
s sat behind the fans. As a hovercraft, the PACV could skim over water, including shallow and reed-choked waters, flat land, and ice. The PACV/ACV was very fast compared to contemporary watercraft, being capable of speeds up to . It had a range of and endurance of seven hours The Army hovercraft, called Air Cushion Vehicles, had more extensive modifications. They had heavier armor and reinforced, load-bearing decks. Army ACVs carried of armor—roughly equal to that of an M113 armored personnel carrier. The armor was thickest around the engine, transmission, and fuel tanks, providing protection from .50 caliber rounds fired at , while the armor around the crew compartment could only block .30 caliber rounds fired at . To save weight, many crews removed the armor around the crew compartment, and an Army evaluation recommended that it be removed altogether because of it "did not provide any protection to the crew," especially against heavier weapons such as
recoilless rifles A recoilless rifle, recoilless launcher or recoilless gun, sometimes abbreviated "RR" or "RCL" (for ReCoilLess) is a type of lightweight artillery system or man-portable launcher that is designed to eject some form of countermass such as propel ...
, artillery, and RPGs. The communications package consisted of a six-station
intercom An intercom, also called an intercommunication device, intercommunicator, or interphone, is a stand-alone voice communications system for use within a building or small collection of buildings which functions independently of the public telephon ...
system,
UHF Ultra high frequency (UHF) is the ITU designation for radio frequencies in the range between 300 megahertz (MHz) and 3 gigahertz (GHz), also known as the decimetre band as the wavelengths range from one meter to one tenth of a meter (on ...
radios, and a radio security set. The boats were shipped with AN/ARC-54
FM radio FM broadcasting is a method of radio broadcasting using frequency modulation (FM). Invented in 1933 by American engineer Edwin Armstrong, wide-band FM is used worldwide to provide high fidelity sound over broadcast radio. FM broadcasting is cap ...
s. However, these proved unreliable, with an operational ready rate of only 35 percent. Army units sought to replace them with VRC-125s. While it is not known if this replacement occurred, one ACV did receive a VRC-46 radio. The hovercraft carried a
Decca Decca may refer to: Music * Decca Records or Decca Music Group, a record label * Decca Gold, a classical music record label owned by Universal Music Group * Decca Broadway, a musical theater record label * Decca Studios, a recording facility in We ...
202
radar Radar is a detection system that uses radio waves to determine the distance (''ranging''), angle, and radial velocity of objects relative to the site. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, w ...
with a dish antenna, which could detect targets within . Some Army ACVs were fitted with XM3 Personnel Detectors (better known as XM-3 " people sniffers"), which could detect human emissions including
carbon Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent In chemistry, the valence (US spelling) or valency (British spelling) of an element is the measure of its combining capacity with o ...
and
ammonia Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogenous was ...
. This equipment was used to find hidden enemies.
Dog team A sled dog is a dog trained and used to pull a land vehicle in Dog harness, harness, most commonly a Dog sled, sled over snow. Sled dogs have been used in the Arctic for at least 8,000 years and, along with watercraft, were the only transport ...
s were also sometimes carried to help detect enemies. The radar was found to be very effective, including for navigating in low-visibility and foggy conditions. The PACV was armed with twin
.50 caliber This is a list of firearm cartridges which have bullets in the to caliber range. *''Length'' refers to the cartridge case Case or CASE may refer to: Containers * Case (goods), a package of related merchandise * Cartridge case or casing, a ...
M2 Browning machine gun The M2 machine gun or Browning .50 caliber machine gun (informally, "Ma Deuce") is a heavy machine gun that was designed towards the end of World War I by John Browning. Its design is similar to Browning's earlier M1919 Browning machine gun, w ...
s in a roof-mounted turret in the front and two 7.62mm
M60 machine gun The M60, officially the Machine Gun, Caliber 7.62 mm, M60, is a family of American general-purpose machine guns firing 7.62×51mm NATO cartridges from a disintegrating belt of M13 links. There are several types of ammunition approved for ...
s, one port and one starboard. The Army initially equipped their hovercraft with a
minigun The M134 Minigun is an American 7.62×51mm NATO six-barrel rotary machine gun with a high rate of fire (2,000 to 6,000 rounds per minute). It features a Gatling-style rotating barrel assembly with an external power source, normally an electric ...
and
40 mm 40 mm grenade (also styled 40mm grenade) is a generic class-name for grenade launcher ammunition ( subsonic shells) in caliber. The generic name stems from the fact that several countries have developed or adopted grenade launchers in ...
M5
automatic grenade launcher An automatic grenade launcher (AGL) or grenade machine gun is a grenade launcher that is capable of fully automatic fire, and is typically loaded with either an ammunition belt or magazine. These weapons are often mounted on vehicles or helicopte ...
as well. Only one ACV was outfitted with a grenade launcher, however, and the miniguns were removed to make space for more troops and cargo because it was found to be effective only for suppressive fire. The Army ACVs had other improvements over the Navy PACVs beyond their additional armor, namely a wider cockpit, more
horsepower Horsepower (hp) is a unit of measurement of power, or the rate at which work is done, usually in reference to the output of engines or motors. There are many different standards and types of horsepower. Two common definitions used today are the ...
, two gun positions instead of one, and a flat deck on top of the skirt for troops to ride on.


Operational history

PACVs were first deployed to
Vietnam Vietnam or Viet Nam ( vi, Việt Nam, ), officially the Socialist Republic of Vietnam,., group="n" is a country in Southeast Asia, at the eastern edge of mainland Southeast Asia, with an area of and population of 96 million, making i ...
in May 1966 as PACV Division 107, Task Force 116, where they were used by the Navy for riverine patrol missions in the
Mekong Delta The Mekong Delta ( vi, Đồng bằng Sông Cửu Long, lit=Nine Dragon River Delta or simply vi, Đồng Bằng Sông Mê Kông, lit=Mekong River Delta, label=none), also known as the Western Region ( vi, Miền Tây, links=no) or South-weste ...
and on the
Mekong River The Mekong or Mekong River is a trans-boundary river in East Asia and Southeast Asia. It is the world's twelfth longest river and the third longest in Asia. Its estimated length is , and it drains an area of , discharging of water annuall ...
. Often called "Pac Vees", they were armed with a .50 caliber machine gun mounted on a rotating platform in the front and two side-mounted M60 machine guns. In addition, the crew, and often US Army
Special Forces Special forces and special operations forces (SOF) are military units trained to conduct special operations. NATO has defined special operations as "military activities conducted by specially designated, organized, selected, trained and equip ...
and
ARVN Ranger The Vietnamese Rangers ( vi, Biệt Động Quân), commonly known as the ARVN Rangers, were the light infantry of the Army of the Republic of Vietnam. Trained and assisted by American Special Forces and Ranger advisers, the Vietnamese Ranger ...
s, riding on the side panels, employed assorted
small arms A firearm is any type of gun designed to be readily carried and used by an individual. The term is legally defined further in different countries (see Legal definitions). The first firearms originated in 10th-century China, when bamboo tubes c ...
such as
M16 rifle The M16 rifle (officially designated Rifle, Caliber 5.56 mm, M16) is a family of military rifles adapted from the ArmaLite AR-15 rifle for the United States military. The original M16 rifle was a 5.56×45mm automatic rifle with a 20-roun ...
s and
M79 grenade launcher The M79 grenade launcher is a single-shot, shoulder-fired, break-action grenade launcher that fires a 40×46mm grenade, which uses what the US Army calls the High-Low Propulsion System to keep recoil forces low, and first appeared during the V ...
s as well as various other rifles, .45 pistols,
light Light or visible light is electromagnetic radiation that can be perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 tera ...
and
medium machine gun A medium machine gun (MMG), in modern terms, usually refers to a belt-fed machine gun firing a full-powered rifle cartridge, and is considered "medium" in weight (). Medium machine guns are light enough to be infantry-portable (as opposed to a he ...
s, and
grenade A grenade is an explosive weapon typically thrown by hand (also called hand grenade), but can also refer to a shell (explosive projectile) shot from the muzzle of a rifle (as a rifle grenade) or a grenade launcher. A modern hand grenade genera ...
s, although using small arms was dangerous because spent casings could fall into the propeller. The PACV was used to prevent Viet Cong infiltration from the sea and tidal areas along river mouths and deltas. It was especially useful in shallow marshy areas, especially the Mekong Delta, where other patrol boats such as the
Patrol Boat, River Patrol Boat, Riverine, or PBR, is the United States Navy designation for a small rigid- hulled patrol boat used in the Vietnam War from March 1966 until 1975. They were deployed in a force that grew to 250 boats, the most common craft in the ...
or
Patrol Craft Fast Patrol Craft Fast (PCF), also known as Swift Boats, were all-aluminum, long, shallow-draft vessels operated by the United States Navy, initially to patrol the coastal areas and later for work in the interior waterways as part of the brown-wate ...
(Swift boat) could not go. The PACV's relatively light weight of only seven tonnes meant that it could be easily carried by a
CH-54 The Sikorsky CH-54 Tarhe is an American twin-engine heavy-lift helicopter designed by Sikorsky Aircraft for the United States Army. It is named after Tarhe, an 18th-century chief of the Wyandot Indian tribe whose nickname was "The Crane". The c ...
helicopter. This allowed it to be airlifted between forward operating bases or transported back to base when it suffered damage. The PACV could also be split into sections and then transported in
Air Force An air force – in the broadest sense – is the national military branch that primarily conducts aerial warfare. More specifically, it is the branch of a nation's armed services that is responsible for aerial warfare as distinct from an a ...
transport planes, which was how they were brought to Vietnam. Navy PACVs were deployed in Operations Game Warden and
Market Time Operation Market Time was the United States Navy, Republic of Vietnam Navy and Royal Australian Navy operation begun in 1965 to stop the flow of troops, war material, and supplies by sea, coast, and rivers, from North Vietnam into parts of Sou ...
, the Navy's operations to deny Viet Cong access to resources in the Mekong Delta and prevent North Vietnamese weapons, fighters, and supplies from entering South Vietnam, respectively. The PACVs were deemed unsuitable for Operation Game Warden because of their "mechanical unreliability" and the limitations imposed on them by terrain. As a result, they were removed from the operation and transferred to another Navy unit, CTF 117. They were also found unsuitable for Market Time operations after serving in that operation from 20 September to 17 October 1966, due to their high noise, low visibility, high cost, and limited utility on the high seas or in narrow waterways. In November 1966, the Navy PACVs were used to great effect in Operation Quai Vat (Vietnamese for "Monster", which was what the Viet Cong called the PACVs). In the operation on the
Plain of Reeds Plain of Reeds (in vi, Đồng Tháp Mười) is an inland wetland in Vietnam's Mekong Delta. Most of the wetlands are within Long An Province and Đồng Tháp Province. Physical characteristics Đồng Tháp Mười is a "back swamp" forming ...
, conducted jointly with Vietnamese
Civilian Irregular Defense Group The Civilian Irregular Defense Group (CIDG, pronounced "sid-gee") was a military program developed by the Central Intelligence Agency (CIA) during the Vietnam War, which was intended to develop South Vietnamese irregular military units from indig ...
(CIDG) troops and Army helicopters and special forces, the PACV force brought its speed and firepower to bear on the Viet Cong, killing at least 23 of them, destroying 70 of their
sampan A sampan is a relatively flat-bottomed Chinese and Malay wooden boat. Some sampans include a small shelter on board and may be used as a permanent habitation on inland waters. The design closely resembles Western hard chine boats like th ...
s and an equal number of their structures, taking many prisoners, and capturing their supplies. This demonstration of combat prowess in the marshy terrain in southwestern Vietnam formed the basis for stationing the Army ACVs in the Plain of Reeds along the South Vietnamese/Cambodian border. An Army evaluation found that in the Plain of Reeds, "any mission requiring ground operations can best be accomplished by ACV unts," particularly reconnaissance, light assaults, infantry transport, canal security, cordoning off areas to prevent escape, and patrolling. Though the loud noise of the PACVs was an issue, their speed made up for it in this otherwise difficult terrain, especially during the
monsoon season The wet season (sometimes called the Rainy season) is the time of year when most of a region's average annual rainfall occurs. It is the time of year where the majority of a country's or region's annual precipitation occurs. Generally, the sea ...
. The PACV could clear
rice paddy A paddy field is a flooded field of arable land used for growing semiaquatic crops, most notably rice and taro. It originates from the Neolithic rice-farming cultures of the Yangtze River basin in southern China, associated with pre-Au ...
dike Dyke (UK) or dike (US) may refer to: General uses * Dyke (slang), a slang word meaning "lesbian" * Dike (geology), a subvertical sheet-like intrusion of magma or sediment * Dike (mythology), ''Dikē'', the Greek goddess of moral justice * Dikes, ...
s and other solid obstacles up to high and negotiate slopes of up to . However, the PACV did not perform well in the dry season, with an Army evaluation noting that "The wetter the season, the better for vehicle operations". The Navy withdrew the PACVs for overhaul in January 1967 and redeployed them to Vietnam in early 1968. Also in 1968, the Army began employing its version of the PACV, the ACV. The Army acquired the vehicles and activated their unit, the 39th Cavalry Platoon, in January before deploying them to Vietnam in April. There were only three Navy PACVs and three Army ACVs during the whole Vietnam War. Two of the three ACVs (No. 901 and 902) were Assault Air Cushion Vehicles (AACV), weapons-heavy vessels configured for attack missions, while the other (No. 903) was a Transport Air Cushion Vehicle (TACV) configured for logistics missions. The TACV only carried the twin M60s, forgoing the .50 cal and other weapons to increase space in the cabin for carrying troops. Both AACVs were lost to Viet Cong attacks. Navy PACVs were based out of
Cat Lo Naval Base Cat Lo Naval Base is a former United States Navy, U.S. Coast Guard, and Republic of Vietnam Navy (RVNN) base approximately northeast of Vũng Tàu in southern Vietnam that was used during the Vietnam War. History In October 1965, the U.S. Navy ...
and operated by Task Forces 116 and 117. The three Army ACVs were operated by the 39th Cavalry Platoon, 9th Division, and were based out of
Ben Luc Ben is frequently used as a shortened version of the given names Benjamin (name), Benjamin, Benedict (given name), Benedict, Bennett (name), Bennett or Benson (given name), Benson, and is also a given name in its own right. Ben (Hebrew), Ben (in ...
and
Đồng Tâm Base Camp Đồng Tâm Base Camp (also known as Đồng Tâm Army Airfield) is a former U.S. Army, U.S. Navy, and Army of the Republic of Vietnam (ARVN) base west of Mỹ Tho in the Mekong Delta, southern Vietnam. History 1966–9 Đồng Tâm Base C ...
, although they often deployed from
fire support base A fire support base (FSB, firebase or FB) is a temporary military encampment to provide artillery fire support to infantry operating in areas beyond the normal range of fire support from their own base camps. FSBs follow a number of plans, their ...
s. The
Green Berets The United States Army Special Forces (SF), colloquially known as the "Green Berets" due to their distinctive service headgear, are a special operations force of the United States Army. The Green Berets are geared towards nine doctrinal m ...
stationed in
Moc Hoa MOC, MoC, or moc may refer to: In government and politics * Member of Congress * Ministry of Commerce * Ministry of Communications * Ministry of Construction * Ministry of Culture In religion * Macedonian Orthodox Church * Masorti on Campus, a Je ...
became proponents of the PACVs, using them in many of their early operations.
Search and destroy Search and destroy, seek and destroy, or simply S&D is a military strategy best known for its employment in the Malayan Emergency and the Vietnam War. The strategy consists of inserting ground forces into hostile territory, ''search''ing out ...
raids conducted out of Moc Hoa in November 1966 caught the Viet Cong by surprise and resulted in many Viet Cong deaths. The PACV's speed, maneuverability, and firepower lent themselves to many types of missions, including patrolling, search and destroy, escorting other ships, raiding, reconnaissance, medical evacuation, transporting artillery pieces, and providing fire support to infantry. It was best suited for ambushes and raids, especially at night, when it could be easily concealed behind reeds and swamp grass. Although it was too loud to be very effective at surprise attacks, it could use its speed to raid Viet Cong bases and escape before they could react. The PACV was found to be most effective when employed in
combined arms Combined arms is an approach to warfare War is an intense armed conflict between states, governments, societies, or paramilitary groups such as mercenaries, insurgents, and militias. It is generally characterized by extreme vio ...
operations alongside helicopters, artillery, and other watercraft; patrol missions conducted in concert with
air cavalry For much of history, humans have used some form of cavalry for war and, as a result, cavalry tactics have evolved over time. Tactically, the main advantages of cavalry over infantry troops were greater mobility, a larger impact, and a higher pos ...
or
Hurricane Aircat The Hurricane Aircat was an airboat used as a riverine patrol boat by the US Army and South Vietnamese Army (ARVN) during the Vietnam War. It was used to conduct various counterinsurgency (COIN) and patrol missions in riverine and marshy areas wh ...
airboat An airboat (also known as a planeboat, swamp boat, bayou boat, or fanboat) is a flat-bottomed watercraft propelled by an aircraft-type propeller and powered by either an aircraft or automotive engine. In early aviation history the term ''airboat ...
s were found to be especially effective. The PACV's low profile and radar also meant that it was used as a stealthy stationary radar station when its engines were off. However, Army evaluations found that the ACV had insufficient firepower, being unable to damage armored or fortified targets, and recommended that it be outfitted with heavier weapons such as
TOW missile The BGM-71 TOW ("Tube-launched, Optically tracked, Wire-guided") is an American anti-tank missile. TOW replaced much smaller missiles like the SS.10 and ENTAC, offering roughly twice the effective range, a more powerful warhead, and a greatly ...
s, 20mm autocannons (such as the M139 or
M61 Vulcan The M61 Vulcan is a hydraulically, electrically, or pneumatically driven, six-barrel, air-cooled, electrically fired Gatling-style rotary cannon which fires rounds at an extremely high rate (typically 6,000 rounds per minute). The M61 and its ...
), or 106mm
M40 recoilless rifle The M40 recoilless rifle is a portable, crew-served 105 mm recoilless rifle made in the United States. Intended primarily as an anti-tank weapon, it could also be employed in an antipersonnel role with the use of an antipersonnel-tracer fl ...
. They also found that it could be too loud to be used effectively for patrol and interdiction missions. Fuel resupply was another frequently cited issue for longer missions, especially given that no adequate method of refueling in the field existed. The PACV was frequently compared to a helicopter because of its speed, terrain crossing ability, maintenance requirements, and cost. Army ACV units operated similarly to
air cavalry For much of history, humans have used some form of cavalry for war and, as a result, cavalry tactics have evolved over time. Tactically, the main advantages of cavalry over infantry troops were greater mobility, a larger impact, and a higher pos ...
. Operating these highly specialized vehicles required pilots and maintenance personnel undergo considerable training, with pilots requiring 75–100 hours of flight experience before participating in combat. Training requirements meant that the Army had to set one craft aside for training for 14 days every month. Troops riding in and on the PACVs also needed training to use them safely: during evaluation, one soldier died when he fell into the hovercraft's intake, and another lost his hand to the propeller. Another downside of the PACV was the degree of maintenance it required: each hour of operation required 20 hours of maintenance, double the 10-hour average for contemporary military helicopters. An Army evaluation found that the PACV had an operationally ready rate of 55.7 percent, and all three Army ACVs were only operational during June 1969. This maintenance requirement, which was made even worse when the vehicles suffered damage, combined with the insufficient firepower to lead an Army evaluation to conclude that "there is no hope of the ACV/ACVunit fighting to a satisfactory conclusion in any large engagement." The PACV was also very expensive, costing about $1 million each,Equivalent to $7.75 million in 2019 as much as 13
Patrol Boat, River Patrol Boat, Riverine, or PBR, is the United States Navy designation for a small rigid- hulled patrol boat used in the Vietnam War from March 1966 until 1975. They were deployed in a force that grew to 250 boats, the most common craft in the ...
s. Because of their high profile and degree of threat, the PACVs and ACVs in Vietnam became major targets. The Viet Cong used ambushes and
naval mine A naval mine is a self-contained explosive device placed in water to damage or destroy surface ships or submarines. Unlike depth charges, mines are deposited and left to wait until they are triggered by the approach of, or contact with, any ...
s against the PACVs. Mines proved especially effective: Army ACV 902 was destroyed by a
tripwire A tripwire is a passive triggering mechanism. Typically, a wire or cord is attached to a device for detecting or reacting to physical movement. Military applications Such tripwires may be attached to one or more mines – especially fragme ...
-triggered mine on 9 January 1970. Though no one onboard was killed, 14 men were injured and the attack slowed the pace of ACV operations because of Army regulations stipulating that the hovercraft work in pairs to protect each other. When ACV 901 was destroyed by a command-detonated mine on 3 August 1970, killing three, the ACVs were deactivated. The 39th ACV Platoon ceased operations on 31 August 1970 and officially left Vietnam in September, transferring their sole surviving ACV to the Army Transportation Museum in Virginia. Navy PACVs returned to the continental United States that August as well. In total, Navy PACVs saw more than 4,500 hours of operation.


Postwar


US Coast Guard service

Following their withdrawal in 1970, the Navy PACVs were transferred to the U.S. Coast Guard for evaluation. The Coast Guard used PACVs, which they called Air Cushion Vehicles (ACVs), through 1975, when they cancelled the ACV program due to budget constraints. Two were stationed at
Fort Point, San Francisco Fort Point is a masonry Seacoast defense in the United States, seacoast fortification located on the southern side of the Golden Gate at the entrance to San Francisco Bay. It is also the geographic name of the promontory upon which the fort and th ...
and the third was used for Arctic Trials in
Point Barrow, Alaska Point Barrow or Nuvuk is a headland on the Arctic coast in the U.S. state of Alaska, northeast of Utqiaġvik (formerly Barrow). It is the northernmost point of all the territory of the United States, at , south of the North Pole. (The northe ...
, though they were also tested in the
Great Lakes The Great Lakes, also called the Great Lakes of North America, are a series of large interconnected freshwater lakes in the mid-east region of North America that connect to the Atlantic Ocean via the Saint Lawrence River. There are five lakes ...
and
Chesapeake Bay The Chesapeake Bay ( ) is the largest estuary in the United States. The Bay is located in the Mid-Atlantic (United States), Mid-Atlantic region and is primarily separated from the Atlantic Ocean by the Delmarva Peninsula (including the parts: the ...
. The Coast Guard PACVs were modified to meet their requirements by replacing the .50 cal gun mount with an observation dome and adding a KAAR LN66 radar and
search-and-rescue Search and rescue (SAR) is the search for and provision of aid to people who are in distress or imminent danger. The general field of search and rescue includes many specialty sub-fields, typically determined by the type of terrain the search ...
equipment. Coast Guard PACVs were crewed by 3—operator, radar operator and navigator, and search-and-rescue crewman—and could carry 6 passengers and half a ton of cargo. Because it was lighter than the military version, the Coast Guard ACV could go up to and had a range of . The ACVs in Coast Guard service were used primarily for
search-and-rescue Search and rescue (SAR) is the search for and provision of aid to people who are in distress or imminent danger. The general field of search and rescue includes many specialty sub-fields, typically determined by the type of terrain the search ...
missions because of their speed and range. In over 185 search-and-rescue missions, they towed boats up to long and recovered survivors from the water and then rushed them to the shore. However, they were also used to service
buoy A buoy () is a floating device that can have many purposes. It can be anchored (stationary) or allowed to drift with ocean currents. Types Navigational buoys * Race course marker buoys are used for buoy racing, the most prevalent form of yac ...
s, resupply and repair remote lighthouses and
lightships Lightship may refer to: * Lightvessel, a moored ship that has light beacons mounted as navigational aids * ''The Lightship'', a 1985 American drama film directed by Jerzy Skolimowski *''The Lightship (novel)'', by Siegfried Lenz on which the film w ...
, enforce laws, clean up oil spills, and ferry personnel and supplies. For minor repairs to buoys, the ACV shortened what was normally a full day mission by a fully crewed ship to a 2-3 hour one by an ACV with three crew members. The ACV was fast enough that it was able to respond to search-and-rescue calls while servicing buoys, something that was not possible for regular
Coast Guard cutter United States Coast Guard Cutter is the term used by the U.S. Coast Guard for its commissioned vessels. They are or greater in length and have a permanently assigned crew with accommodations aboard. They carry the ship prefix USCGC. History ...
s. However, servicing structures in choppy weather on the open sea was found to be dangerous. The ACV proved particularly effective in the Arctic because it could traverse water and ice equally well at high speeds, although crews did encounter some issues relating to windshield icing. At least one ACV was active in
San Francisco Bay San Francisco Bay is a large tidal estuary in the U.S. state of California, and gives its name to the San Francisco Bay Area. It is dominated by the big cities of San Francisco, San Jose, and Oakland. San Francisco Bay drains water from a ...
24/7, and a special hangar for the ACVs was built at the Coast Guard Station at Fort Point from August 1970 to 1972.The episode "Deathwatch" of
The Streets of San Francisco ''The Streets of San Francisco'' is a television crime drama filmed on location in San Francisco and produced by Quinn Martin, Quinn Martin Productions, with the first season produced in association with Warner Bros. Television (QM produced the ...
was filmed in 1972 and features an ACV in the climactic scene.
The San Francisco ACVs were evaluated for use as a crash/fire rescue vehicle at
Oakland International Airport Oakland International Airport is an international airport in Oakland, California, United States, 10 miles (16 km) south of downtown located in the San Francisco Bay Area. It is owned by the Port of Oakland and has domestic passenger f ...
in 1972 and were found to be successful. One of the San Francisco-based ACVs was showcased by the Coast Guard at the
U.S. International Transportation Exposition U.S. International Transportation Exposition, better known as Transpo '72, was a trade show held on of land at Dulles International Airport outside Washington, D.C., for nine days from May 27 to June 4, 1972. The $10 million event, sponsored by t ...
at
Dulles International Airport Washington Dulles International Airport , typically referred to as Dulles International Airport, Dulles Airport, Washington Dulles, or simply Dulles ( ), is an international airport in the Eastern United States, located in Loudoun County and Fai ...
in 1972, where it was inspected by tens of thousands of international visitors. Over the first two years of evaluation, the Coast Guard ACVs accrued over 1,500 hours of operating time. As part of the evaluation, the ACV at Point Barrow was transferred to
Traverse City, Michigan Traverse City ( ) is a city in the U.S. state of Michigan. It is the county seat of Grand Traverse County, although a small portion extends into Leelanau County. It is the largest city in the 21-county Northern Michigan region. The population was ...
for refurbishment and then stationed at St. Ignace Coast Guard Station on
Lake Huron Lake Huron ( ) is one of the five Great Lakes of North America. Hydrology, Hydrologically, it comprises the easterly portion of Lake Michigan–Huron, having the same surface elevation as Lake Michigan, to which it is connected by the , Strait ...
. It sank on 23 November 1971 after only 26 hours of operation in Lake Huron, after the cabin was breached by a rock and the engine inexplicably failed, leading the craft to take on water and sink. After this sinking, one of the two San Francisco ACVs was then transferred to the Great Lakes. Another was transferred to the East Coast, where it performed aids to navigation survey/inspection and search-and-rescue operations on Chesapeake Bay, while the third remained in San Francisco Bay. The Chesapeake ACV was found to be particularly valuable for search-and-rescue operations in marshy or shallow waters. In the final Coast Guard evaluation, Commander Thomas Lutton wrote that "The ACV has dramatically and repeatedly demonstrated its capability to effectively perform a wide range of Coast Guard missions." However, the Coast Guard was in the middle of a large upgrade of its other boats and cutters at the time and so did not have the money to acquire ACVs. As such, the two surviving ACVs were transferred to US Army Mobility Equipment Research and Development Center in
Fort Belvoir, Virginia A fortification is a military construction or building designed for the defense of territories in warfare, and is also used to establish rule in a region during peacetime. The term is derived from Latin ''fortis'' ("strong") and ''facere'' ...
, on 25 April 1975.


Survivors

*The sole surviving Army ACV (No. 903) was transferred to the
U.S. Army Transportation Museum The U.S. Army Transportation Museum is a United States Army museum of vehicles and other transportation-related equipment and memorabilia. It is located on the grounds of Fort Eustis, Virginia, in Newport News, on the Virginia Peninsula. History ...
in
Fort Eustis Fort Eustis is a United States Army installation in Newport News, Virginia. In 2010, it was combined with nearby Langley Air Force Base to form Joint Base Langley–Eustis. The post is the home to the United States Army Training and Doctrine Co ...
,
Virginia Virginia, officially the Commonwealth of Virginia, is a state in the Mid-Atlantic and Southeastern regions of the United States, between the Atlantic Coast and the Appalachian Mountains. The geography and climate of the Commonwealth ar ...
, where it is still on display . *The only surviving US Navy PACV (No. 004) is preserved at the
Yanks Air Museum The Yanks Air Museum is a non-profit 501 (c)(3) organization and museum dedicated to exhibiting, preserving and restoring American aircraft and artifacts in order to show the evolution of American aviation, located at Chino Airport in Chino, Calif ...
in
Chino, California Chino ( ; Spanish for "Curly") is a city in the western end of San Bernardino County, California, United States, with Los Angeles County to its west and Orange County to its south in the Southern California region. Chino is adjacent to Chino ...
.


See also

*
Hurricane Aircat The Hurricane Aircat was an airboat used as a riverine patrol boat by the US Army and South Vietnamese Army (ARVN) during the Vietnam War. It was used to conduct various counterinsurgency (COIN) and patrol missions in riverine and marshy areas wh ...
*
LACV-30 The LACV-30 (Lighter Air Cushion Vehicle, 30 tons) was a hovercraft used by the U.S. Army Mobility Equipment Research and Development Command (MERADCOM) for offloading cargo from amphibious ships. For logistic transport, the Army was already usin ...
*
Landing Craft Air Cushion The Landing Craft Air Cushion (LCAC) is a class of air-cushioned landing craft (hovercraft) used by the United States Navy and the Japan Maritime Self-Defense Force (JMSDF). They transport weapons systems, equipment, cargo and personnel from shi ...


Notes


References


External links

{{Commons category, Patrol Air Cushion Vehicle
Hovercraft Museum: SR.N5


Video
Patrol Air Cushion Vehicles (PACV) used in Vietnam in conjunction with Bell UH-1 Iroquois Huey helicopters
Military hovercraft Riverine warfare History of the United States Navy Vietnam War ships of the United States Amphibious warfare vessel classes Ships of the United States Army