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Mechanized Landing Craft LCM

Almost everyone who has ever watched a war movie have seen LCMs in action. With their huge bow ramps that drop to allow men and equipment they carry to "hit the beach" in an amphibious assault, they are the link between the beach and the large transport ships that sit offshore. Called boats instead of ships because of their size and affectionately referred to as "Mike" boats by those who love them, the Landing Craft, Mechanized (LCM) plays a vital role in the Navy's amphibious assault mission.

The initiative in development of large landing craft was left to the British who, for obvious reasons, were much more seriously impressed with the need for such craft. British experimentation with specialized landing craft began after World War I as a result of the invention of the tank. Whereas experience had seemed to show that personnel could be landed on hostile shores by the regular vessels of the fleet, the tank clearly could be beached only from a special ramp boat. In 1920 the British produced a tank lighter which, with very few changes, became the LCM(l) (Landing Craft, Mechanized). Too small to carry the medium tanks used in World War II, the LCM (l) was nevertheless kept in extensive use for transporting other vehicles and supplies.

The LCM and LCA were designed for raiding operations. Production was undertaken only on a very small scale and mostly outside the established shipbuilding industry which was already working to capacity in attempting to meet vastly expanded requirements for merchant and naval war vessels. Engines for both the LCM and LCA came from the United States.

The LCM may be thought of as a big and chunky older brother to the LCVP. They show a distinct family resemblance as brothers often do, but the "M(3)" has larger "muscles." It carries more cargo, has more power, and is more difficult to operate. Like the "VP," the "M(3)" must pound in through the breakers, beach, unload, retract, and return successfully for another load. Into its sturdy all steel hull the same qualities required of the LCVP have been built: speed, lightness, power, toughness, long cruising range, sizeable cargo capacity, maneuverability, armament, and simplicity. In the hands of a capable crew, this boat has what it takes to pour men and material onto a beachhead.

The LCM(3) is 50 feet long with a beam of 14 feet. She weighs about 25 tons and has a cargo space 32 by 91/2 in which a 30-ton tank can be carried. (Because of this ability to ferry tanks, this boat is sometimes called a tank lighter.) If not transporting a vehicle, the "M(3)" can take 60,000 pounds of cargo or 120 troops ashore on each run. The tank lighter's power plant consists of two 225-horsepower Gray Marine Diesels supplied by twin fuel tanks with a total capacity of 400 gallons. This is sufficient oil for a 125-mile trip. Two screws and twin rudders drive and direct the LCM through the water at a normal operating speed of 10 miles per hour.

A five man crew is required to handle the LCM(3): a coxswain, engineer, and three deck hands. The coxswain must be unusually skilled in handling boats since the task of manipulating the controls for two engines is fairly complicated. Also, the boat handles in a tricky fashion because of its shallow draft and high freeboard. So that it can be driven well up on the beach, the tank lighter has a very shallow draft forward, and but a few feet aft. A skeg gives protection to rudders and screw. As in the case of the LCVP, armor plating protects the crew, and machine guns mounted aft near the pilot house provide a measure of defense from shore fire and strafing.

There are several ways in which the LCM(3) is distinctly different from the LCVP. The twin engine construction is but one of these differences. Others include the power operated ramp, the wing tanks, and the more complicated structure of the after section: engine room, lazarette, and pilot house.

The heave ramp is driven by the port engine and operated by the coxswain. When ready to lower it, he instructs one of the deckhands to release the ramp safety chain or hook, then depresses a foot pedal in the pilot house to free the ramp latch, engages the clutch of the ramp hoist control, and lowers away. The wing tanks extend the length of the LCM. They are divided into water-tight compartments, as is the double hull, and are reinforced by stout metal beams. The buoyancy these tanks provide will keep the boat afloat even when the cargo space is flooded.

Directly forward of the pilot house a small hatch gives access to the engine room. The twin diesels are mounted to port and starboard of the keel and are separated by a catwalk, from which the engineer can work. Abaft the engine room is a second tiny compartment or space, the lazarette. The steering mechanism is located here. A second small hatch on the transom abaft the pilot house open into the lazarette. The pilot house is made of steel plate and is equipped with peep holes to eliminate the need for the coxswain to expose his head to small arms fire when moving toward the beach. Within are the steering wheel, instrument panels for each engine, and engine and ramp controls. Another value of the pilot house is the protection it affords against heavy surf.

The LCM(6) is intended primarily for the transport of cargo and/or personnel from ship-to-ship and ship-to-shore. The craft is a 56-foot twin-screw, welded-steel craft with forward cargo well and bow ramp. The design of the boat permits its transportation aboard larger vessels.

In 1959, the LCM-3 was replaced with the larger 70 ton LCM-8, known to the Marines at the Mike boat. LCM-8 are manned by a four man crew, Boatswainmate Petty Officer, Enginerman Petty Officer, and a nonrate fireman and seaman. The LCM-8 is constructed of steel and powered by two 12 V-71 diesel engines. The LCM-8 has twin screws and rudders, which can be controlled from the pilothouse. LCM-8 is built of welded steel; it's bottom, however, is semiflat. Capable of carrying 60 tons of cargo, the LCM is a highly-versatile workhorse for the amphibious force commander.

The Army must deploy and sustain forces in an overseas theater in support of the Army Strategic Mobility Program (ASMP). This includes conducting port operations in port facilities or during logistics-over-the-shore (LOTS) operations. These operations currently lack afloat C2 platforms to direct and monitor cargo discharging and loading. Waterborne logistics will deliver 90% of all unit warfighting equipment and supplies. Army watercraft including landing craft, amphibians, modular causeways and harbor craft provide the critical link between the offshore arrival of combat power on strategic sealift and placing that power ashore in a combat configuration. The Mod 2 will perform a multi-faceted role in theater opening and force sustainment operations. The Mod 2 supports ASMP guidance and FORCE XXI initiatives.

The LCM-8 Mod 2 will function as a command and control (C2), personnel transfer and a light salvage/firefighting vessel. The Army will modify existing LCM-8s for this purpose. The total requirement for the Mod 2 is 14 (4 Prepo, 5 AC, 5 RC). The LCM-8 Mod 2 will perform many key support functions in conditions through sea state 3. The LCM-8's proven record of performance provides a solid platform for this modification. As a C2 platform, the Mod 2 will provide the critical link between ship and shore operation centers. It will transport Army stevedores from shore to ship/ship to shore in a protected environment. It will also be used as a MEDEVAC vessel, diver support platform, limited firefighting and light salvage boat. The Mod 2 will function in shallow inlets, rivers and surf zones. It will retain its ability to land on an unimproved beach.

The LCM-8 transports cargo, troops, and vehicles from ship to shore or in retrograde movements. It is also used in lighter and utility work in harbors. The LCM-8 is designed for use in rough or exposed waters and can be operated through breakers and grounded on the beach. The bow ramp allows RORO operations with wheeled and tracked vehicles. Its small size allows for use in confined areas. The LCM-8 can be transported by LSVs, LCU 2000s, LSTs, commercial bulk carriers, and heavy lift ships.

In December 2002 Naval Surface Warfare Center announced plans for an LCM8 Replacement. It was anticipated that a quantity of up to 50 craft may ultimately be procured, for implementation as replacements of the Landing Craft, Mechanized (otherwise known as "LCM(8)") platforms currently in service with the Maritime Prepositiong Ships of the Military Sealift Command (MSC).

The candidate craft must be capable of the following mission objectives: 1) safe transfer of up to 30 personnel and baggage from a MSC ship to undeveloped shoreline and return, with an expected standoff distance from shore of at least 25 miles; 2) conducting intentional beach landings for transfer of personnel and material, through the use of a self-contained ramp or brow; 3) providing medical evacuation to or from ship to undeveloped shoreline for at least two injured ind ividuals, a Corpsman and medical equipment, in a stable and secure condition; 4) conducting bottom survey in a surf zone, including the capability of subsequently transmitting survey findings to ship or shore; 5) providing afloat protection to MSC vessels while on station, through an inherent capability to mount weapons of up to .50 caliber, i.e., M2-HB Browning machine gun(s).

In contrast to the LCM(8), the candidate craft will NOT be required to retain the ability to transport any tracked or wheeled vehicles as cargo, only personnel and associated equipment. The candidate craft must be capable of the following performance objectives: 1) maintaining a top speed of at least 25 knots in a full-load condition; 2) being operated without limitation in environmental conditions of Sea State 2, 3) surviving in Sea State 5.

The candidate craft must be capable of the following interoperability objectives: 1) the ability to be loaded and transported onboard any of the 16 existing MSC Maritime Prepositioning Ships. 2) occupying less space and weight than the existing LCM(8) craft on the Maritime Prepositioning Ships.

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Page last modified: 02-12-2019 18:21:41 ZULU