LCM-8

From Wikipedia, the free encyclopedia

LCM-8 in March 1972
Class overview
Name: LCM-8
In service: 1959 to present
General characteristics
Type: Mechanized landing craft
Displacement: 57.8 long tons (58.7 t) light
111.4 long tons (113.2 t) loaded
Length: 73 ft 7⁄12 in (22.265 m)
Beam: 21 ft 0 in (6.4 m)
Draft: 4 ft 7⁄12 in (1.234 m) light
5 ft 3 in (1.60 m) loaded
Propulsion: (original) 4, 2-twin-pak GMC6-71 or Gray Marine 6-71 diesel paired to 2 hydrostatic transmissions Detroit 12V-71 diesel engines, twin screws
Speed: 12 knots (22 km/h) light
9 knots (17 km/h) loaded
Capacity: 53.5 long tons (54.4 t) of cargo
Complement: 4–6
Armament: 2 × 12.7 mm machine guns

The LCM-8 ("Mike Boat") is a river boat and mechanized landing craft used by the United States Navy and Army during the Vietnam War and subsequent operations. They are currently used by governments and private organizations throughout the world. The acronym stands for "Landing Craft Mechanized, Mark 8". (The "Mike Boat" term refers to the military phonetic alphabet, LCM being "Lima Charley Mike".)

The vessel weighs 135,000 pounds (61,200 kg) and has a crew of four: a Boatswain's Mate petty officer, an Engineman petty officer, a non-rated fireman, and a seaman. US Army specifications call for a crew of six: two coxswains, two seaman and two enginemen. The LCM-8s are constructed from welded steel and powered by two 12 V-71 diesel engines, twin propeller screws, and rudders. The ship can carry 60 short tons of cargo. It was designed by Marinett Marine Corp Dimensions. It has a range of 190 miles at 9kts full load.

In I Corps (the northernmost military district in Viet Nam) boats based at Da Nang, Tan My and Cua Viet had three man crews of various rates and ranks. The senior rate was usually a third class petty officer or above, and the two crewmen could be E-2, E-3 or E-4 ranks (i.e. seaman apprentice, seaman, or petty officer third class) One of the two crewmen was almost always an Engineman, and could be an ENFA, ENFN, or an EN3C in rank. The LCM-8s there all had two sets of the twin 671 Detroits paired up to a hydro transmission. Two air compressors, port and starboard of the engine sets, provided air pressure to operate the air cylinders that raised and lowered the bow ramp. The air cylinders were below deck in the eighth void from the bow and stretched cables attached to the ramp to raise it. Lowering the ramp was accomplished by releasing the air and allowing gravity to bring the ramp down.

Modifications

A modified version, the Zippo boat, carries flamethrowers.[1] Another modified version, the LCM-8 Mod 2 was used to fulfill command, personnel, salvage, and firefighting functions. There is also another version with an aluminum hull. This version is mostly carried by pre-positioned ships.

A third modification was as a transport for PBRs (patrol boat, river) from repair stations at Da Nang (YR-71) and Tan My (PBR Mobile Base 1) to outlying points at Cua Viet, and the Cua Dai rivers. PBR main propulsion jet pumps were easily damaged by ocean salt water which necessitated the boats being carried by another craft to their duty stations. These transport LCMs were classed as mini-docks and each had a boat ramp in the well deck. The voids (built-in float chambers under the well deck) would be systematically flooded, allowing the front end of the craft to sink, so a PBR could be floated in or out of the well deck. The pumping mechanism would then be reversed to clear the water out of the voids, restoring the craft to normal floating position.

U.S. usage

They were used by the United States Navy and Army during the Vietnam War. During the Vietnam War, there were two new aluminum LCM-8s on Johnston Island, which carried trucks and cargo between islands, and one being used as a rescue boat. They had the newer fluid shift transmissions, and 2-671's paired up to two props. They also saw use during Operation Just Cause in Panama as well as Operation Desert Shield and Operation Desert Storm. Three Army LCM-8s served in the 1992–1993 US mission to Somalia (fictionalized in Christian Bauman's 2002 novel The Ice Beneath You, which is set in part on a US Army LCM-8 near Kismaayo, Somalia), and a platoon of LCM-8s from the 1098th Trans Co. deployed to Port-au-Prince for the Haitian invasion (1994). The United States Army Reserve's 464th Transportation Company assisted the United States Coast Guard in patrolling the Potomac River after the terrorist attacks on September 11, 2001.

Some are currently deployed aboard Maritime Prepositioning ships to facilitate their mission of being able to unload all their cargo while still offshore with no outside assistance.

Australian service

Australian Army LCM-8 showing the extended wheelhouse of the Australian vessels, off Palm Island, Queensland in 2005

Eleven of the LCM-8s were constructed from 1965 to 1967 for the Australian Army as heavily modified version, crewed (four) and administered by the Royal Australian Corps of Transport and one engineer from the Royal Australian Electrical and Mechanical Engineers (RAEME). The modifications of the vessels includes an extended enclosed wheelhouse that included full galley facilities, chart table and storage space to aid in extended operations beyond the original design parameters. A water purification system allows the vessels to be somewhat independent for longer periods of time. A fully functioning toilet (head) and shower are also installed as part of the wheelhouse extensions, external provision for bedding is also include for the full crew complement.

The extension of the wheelhouse increased rigidity of the craft leading to excessive vibration and cavitation with the original three-blade propeller. Further development included a more balanced and expensive five-blade propeller, negating the vibration and cavitation of the original. The prop change found a few negative effects in the beaching performance of the vessel but over time tactics have been changed to suit the new system.

The vessels are also installed with a full suite of electronics allowing the craft to navigate in all weather, day or night in military operations anywhere in the world with little to no special training requirements for an indefinite period.

During the mid-1990s, the Army LCM-8 received a life of type extension with a re-engine program to help extend the life of the existing fleet. The original twin-pac 6-71 two-stroke Detroit Diesel engines and Allison mechanical transmissions were replaced with 8v-92 Silver Series Detroit Diesel engines and Allison Hydraulic Transmissions thus extending the life of the craft for another 20 years.

Two craft were utilized during the invasion of Iraq in 2003, patrolling the shallow waters of the Khawr Abd Allah estuary using HMAS Kanimbla as its base of operations. They were extensively used in East Timor for logistic operations in direct support to multinational peace keepers. Other deployments include peacekeeping and peace monitoring operations in Bougainville and the Solomon Islands.

The LCM-8s were to be replaced in by LCM2000 waterjet propelled vessels, but these craft proved too large to be carried on the Kanimbla class vessels and were canceled.[2][3] The ADF has since selected the waterjet LCM-1E to replace the LCM-8s.

Operators

Notes

  1. ↑ "The first Zippo boats were ATCs carrying an M132A1 flame-throwing armored personnel carrier."
    'Another type of boat carried a flamethrower that could shoot a stream of burning liquid several hundred yards. These boats ... were called "Zippo" boats.'
  2. ↑ Williams, Adam (March 2006). "Design and Construction of the Army Watercraft" (PDF). Navy Engineering Bulletin (Royal Australian Navy): 56–58. Retrieved 2008-09-05. 
  3. ↑ Toune, Rachel (29 July 2010). "Million dollar craft lay idle". Townsville Bulletin. Retrieved 1 August 2010. 

External links

Wikimedia Commons has media related to LCM-8.
This article is issued from Wikipedia. The text is available under the Creative Commons Attribution/Share Alike; additional terms may apply for the media files.