Thursday, November 20, 2014

Saturday, November 8, 2014

Air Cushioned Patrol Boat

The PACV ("Patrol Air Cushion Vehicle") was a patrol hovercraft made notable by its involvement in the Vietnam War under the flag of the United States Navy and, later, Army. The system was trialed with good results but limited to just seven total production units made up of four USN PACV trial vessels and three slightly-modified craft for the Army under the designation of "ACV", or "Air Cushion Vehicle" (some sources state only six total PACVs/ACVs were produced). The series became known by the nickname of "Pac Vee", noting its USN "PACV" designation. The Viet Cong feared the capabilities of the PACV/ACV to the extent that they gave it the rightful nickname of "Monster".


Though often betrayed by her operating noise, the PACV/ACV made up for it through speed and firepower and was known as Monster by the Vietcong.
The PACV maintained its origins in an original hovercraft design produced by the British firm of Saunders-Roe. Saunders-Roe had a long history of producing both aircraft and marine vehicles since its founding in 1929. A merger with Westland Aircraft (later Agusta-Westland) ended Saunders-Roe officially as a company by 1964 but the merger gave birth to the British Hovercraft Corporation. The American PACV was developed from the original Saunders-Roe/British Hovercraft Corporation product SR.N5 under the Bell Aerosystems brand. Bell Aerosystems designated their new militarized product as the SK-5. As actions in the Vietnam War were ramping up, the US Navy took note of the machine and decided on a small purchase of these new machines for evaluation in the Theater. Her sailors trained on the waters off Coronado, California near San Diego. Refinements to the design were made based on feedback.


Categorized as a hovercraft, the PACV was capable of skimming the water's surface, able to build a fair amount of forward speed in the process and possess agility quite uncommon to any surface patrol vessel.

Displacement was near 15,600lbs and the PACV featured a bow-to-stern length of 38 feet, 10 inches. Its beam was a reported 23 feet, 9 inches. Maximum speed was listed at 60 knots while a range of 165 nautical miles was possible. The PACV as accurately described as "one-third helicopter, one-third airplane and one-third boat".

The PACV took on a wide and stout external appearance, primarily characterized by her wide-span upper hull and inflated air cushion skirt.

The crew cabin lay in a centralized nacelle just behind the bow and running to about amidships. The GE turboshaft turbine engine was fitted just aft of the crew compartment and powered an elevated three-bladed Hamilton propeller with variable pitch and full reversibility. The propeller system forced air between two vertical tail fins connected via a horizontal plane and allowing for smooth lateral movement as well as forward propulsion. Vertical lift power was supplied to the PACV through a centrifugal 12-bladed blower fan of 7-foot diameter comprising the horizontal lift system. This arrangement served the PACV well and allowed the nimble system the ability to cross over marshland and muddy surfaces with relative ease and at speed.

The crew cabin was windowed along all sides but the rear (this area taken up by the powerplant).

 A radar array was affixed to the top of the cabin. The dorsal gunner emplacement was situated above the cabin and ahead of the radar array. The pilot sat in the forward area of the crew cabin, offset to the right with a commanding view of the forward action. The radar operator was seated opposite him, maintaining a position in the forward-left portion of the crew cabin. Entry and exit was primarily through a flip-up hinged door system fitted to the front of the cabin, splitting the seating areas of the pilot and radar operator. The upper hull worked well as a surface for transporting passengers and gear.


It was not uncommon to see the PACV painted with "shark teeth" along the forward portion of the skirt - this obviously a psychological play against the Viet Cong they would be fighting.
Armament was centralized around a single (or double) Browning M2 .50 caliber machine gun set up affixed to a rotating mount above the crew cabin. This armament was complimented by .30 caliber M60 general purpose machine guns fitted to the sides of the craft. Additionally, 40mm grenade launchers and additional M60 machine guns could be fitted in remote-controlled emplacements at the stern. Beyond that, the PACV crew had access to whatever personal weapons they would take along on a given mission including rifles, automatic weapons and grenades. In addition to the base crew's weapons, the PACV could also make use of any armament brought onboard by its passengers. Many-a-passenger preferred to ride on the outside of the craft with guns at the ready. This made for easier disembarking and allowed the passengers to bring their weapons to bear in support of the crew. In all, this collection of armament options made for one lethal waterborne system on par with other patrol craft operating in Vietnam at the time.




The first PACV were sent and deployed to Vietnam waters sometime in 1966 and were utilized to good effect across the Mekong Delta.

 PACVs operated as experimental evaluation units tied to Task Force 116 and making up PACV Division 107. Combat engagements soon led to additional armoring being added to help support the crew and the delicate subsystems of the PACV. The PACV fought on, out of Moc Hoa, until being recalled for their overhaul in early 1967. These USN PACVs were eventually relegated to state-side duties with the US Coast Guard after their tours in Vietnam had concluded.

Initial actions revealed the PACV to be an effective weapon against the Viet Cong, particularly across soft and wet terrain where no other USN and US Army vehicles could go.



If there was a negative in the legacy of the PACV, it was in the amount of noise being generated from her turbine engine. Thusly, the reach of the PACV was limited to some extent. Additionally, the internal components of the PACVs showed themselves to be too complicated for the daily rigors of riverine warfare in Vietnam where both environment and combat actions could render its subsystems inoperable with relative ease. However, the speed, traversing capabilities and firepower of the PACV were second to none and these benefits - at least for the time being - outweighed the inherent deficiencies in the system. The PACV proved effective in engaging the enemy through sheer force and served well in blocking known supply lines, policing enemy waterways, serving in the fire support role and useful in the extraction of allies in need or special forces operatives.

The US Army teamed up with Bell to develop its own version of the Navy PACV. The resulting design became the ACV which sported a longer and wider appearance and reinforced side decking.

The forward access door was widened and weapons-carrying capabilities were enhanced. The US Army operated their ACVs with an equal level of success against the Viet Cong throughout the "Plain of Reeds" and undertook missions in the training, reconnaissance, supply and assault roles - often serving in pairs for best effect with aerial coverage of a given operation served by helicopters. Army ACVs operated with the US 9th Infantry Division and deployed out of the Dong Tam area (and later Ben Luc). The ACV deployed to Vietnam in May of 1968 as three examples with hull numbers ACV 901, 902 and 903.

ACV 901 and 902 were fully-loaded attack variants complete with the dorsal .50 caliber machine guns, side-mounted M60 machine guns and a 40mm automatic grenade launcher while ACV 903 was set up as an armed transport fitting only the M60 machine guns. ACV 901 was eventually put out of commission for a period of eight months due to an accident leaving the three vessels to served concurrently only in late 1969. ACV 901 and 902 were eventually destroyed in January and August of 1970 respectively while ACV 903 eventually returned state-side to be put on display at the Transportation Museum.

Despite its combat usefulness, the PACV/ACV program was ultimately dropped. The PACV/ACV was a unique vehicle requiring its own unique training.

 Twenty-four personnel made up one operating unit and training spanned some 14 days each month, requiring at least one PACV/ACV to be left behind during this period. ACV crews were called to train their own replacements. Additionally, the mechanical requirements of the PACV/ACV in regards to regular and combat-related maintenance required much attention, with logistical support having to come from long distance state-side sources.

PACV-4 is the only known surviving PACV system. She completed two tours in the Vietnam War before going on to serve in the Canadian Coast Guard during her post-war years.

Specifications for the PACV / ACV (Pac-Vee / Monster)

Dimensions:
Length: 48.55ft (14.80m)
Beam: 25.26ft (7.70m)
Draught: 0ft (0.00m)

Performance:
Surface Speed: 35kts (40mph)
Range: 190miles (306km)

Armament Suite:
In addition to any crew-served weapons (M16, M79, M60 GPMG, etc...), the PACV was fitted with the following:

1 OR 2 x 12.7mm machine guns in forward rotating dorsal rotating position
1 x 7.62mm M60 general purpose machine gun in port side mount.
1 x 7.62mm M60 general purpose machine gun in starboard side mount.

OPTIONAL:
1 OR 2 x 7.62mm M60 general purpose machine gun in remote-controlled stern position(s)
1 OR 2 x 40mm grenade launchers in remote-controlled stern position(s)
Structure:
Complement: 4
Surface Displacement: 10tons


Machinery:
Engine(s): 1 x Rolls-Royce Marine Gnome gasoline turbine developing 900shp driving a BHC 12-blade centrifugal lift fan propeller and Dowty Rotol 4-blade propulsion propeller (SR.N6 Mk 1).


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