LCAC (Landing Craft Air Cushion) Air Cushioned Landing Craft / Hovercraft
LCAC (Landing Craft Air Cushion) Air Cushioned Landing Craft / Hovercraft
The impressive-looking LCAC is currently in active service with American and Japanese naval forces.
Authored By JR Potts, AUS 173d AB; Content ©www.MilitaryFactory.com
The World War 2 Normandy invasion of Europe by Allied forces on June 6th, 1944, was comprised of thousands of ships of all types. The main task of the fleet was to provide shore bombardment and carry the troops, supplies, and armored vehicles going ashore in the 3,500 specialized landing craft.
Up to this point, this operation became the largest recorded use of landing craft in history. LSTs (Landing Ship, Tank) were large craft used to shuttle tanks and armored vehicles to shore while LCIs (Landing Craft, Infantry) were built to accommodate up to 200 troops and the LCA (Landing Craft, Assault) was designed to carry a platoon of 31 infantrymen. By 6:55AM on Omaha Beach, one of the fived named beachheads during the first invasion wave, the 116th Regiment of the 29th Division suffered 99% causalities in just fifteen minutes. As the second wave approached the blood-soaked beach, the landing craft took artillery and mortar rounds fired from German positions ashore, some receiving direct hits and killing all those onboard. When some of the LCA's made it to the beach, the entry-exit ramp along the front of the hull was dropped down, instantly exposing the infantry to a waiting enemy, machine guns trained on the masses of body. It was only a matter of time before German machine gun fire ripped these men to pieces. As other LCAs approached the beach, some coxswains could not see through the smoke covering the beach and became disoriented, dropping their ramps in deep water, forcing the troops to wade ashore in water that was chest high. Many would fall into the sea, drowned by the weight of their own equipment and weaponry. It was obvious that the World War 2-era landing craft were a long way from being efficiently capable of safely landing men and material on enemy shores.
In 1977, amphibious prototype designs were being evaluated for the American military - a program that would eventually produce the "Landing Craft Air Cushion" (LCAC) vehicle. The ambitious purpose of this new design was to supply American war planners with a craft that could effectively conduct an amphibious assault complete with troops, equipment and supplies, while being launched from ships "beyond-the-horizon". This vessel would wade across sea and reach shore and travel over the beach and beyond if need be. The selected prototype was a design sponsored by Bell Aerospace of New Orleans, Louisiana - a firm with experience in building hovercraft that were tested in the Vietnam War. Funding started in 1982 and, by 1987, the first LCAC 1 was deployed aboard the USS Germantown (LSD-42). The last craft, LCAC 91, was delivered to the US Navy in 2001. The largest deployment of these craft to date consisted of 11 examples deployed in the Persian Gulf War during Operation Desert Storm in 1991. None were combat tested however.
The LCAC is launched by any US Navy surface ship featuring a "well deck". To operate the craft, she needs a base crew of five personnel. The craft measures in at 87 feet, 11 inches long (26.4m) and 47 feet wide (14.3 m). Her hull is supported by a cushion of high pressure air that is ejected downward towards the surface below and constricted by a skirt. The LCAC is powered by four main engines that provide lift and propulsion and, much like a helicopter, provides the LCAC with six dimensions of motion. The engines are Avco Lycoming TF40B gas turbines supplying a combined 16,000 shaft horsepower. Two are used for lift and the remaining two are used for propulsion. For propulsion, the LCAC sports 2 x 4 bladed reversible pitch propellers that are 11.75 feet in diameter and navigate the craft like a ship-born vessel's rudder system. For lift, there are 4 x 2 entry double exhaust centrifugal fans that measure up to 63 inches in diameter. The crewman who steers the craft is called the "craftmaster" - a yoke is used along with foot rudder controls to move the craft in any direction. The downward air is enclosed by a flexible rubber canvas skirt system allowing the hull to hover four feet above any surface.
The LCAC maintains 5,000 gallons of internal fuel and the thirsty girl needs 1,000 gallons per hour to operate. Each LCAC fields two ramps - the bow ramp is 28.8 feet wide and the stern ramp is 15 feet. Men and equipment and be unloaded simultaneously to allow the LCAC to return to the fleet for additional men or supplies. The craft can make 40 knots (47mph) under load making her a valuable and fast transport along with her ability to come ashore on 70% of the world's coastlines. She can cross and operate over ice, soft sand, gravel and swampland. The vehicle needs 500 yards to stop and 2000 yards to make a radius turn. The LCAC's downward airflow creates high dust levels, and if disabled, the craft is difficult to tow. She displaces 170 tons when fully loaded while weighing 87.2 tons when light and allows for the transport of 82.7 tons of cargo with her 1,809 sq ft bay. This weight limit supports 180 fully equipped troops or an Abrams main battle tank as well as a variety of armored vehicles or cargo.
In 1996 plans were made to modernize the LCAC. A standard "Service Life Extension Program" (SLEP) was approved in 2004 and called for upgrading all active LCAC's and extending their usefulness some 30 years at about $20 million each. The service program covered upgrades to the onboard electronics as well as a new buoyancy box replacement for each of the 74 craft. The expected new extended life will be from 2014 to 2027 (based on the craft's original launch date).
The primary amphibious assault vehicle used by the USMC (as of 2010) was the AAV-7A1. This tracked armored system can hold 25 troops and can also be launched from well decked ships with a speed of 43 knots but can only access 17% of the world's coast line and has an operational range of 300 miles. However, unlike the LCAC, the AAV is not an "over the horizon" assault vehicle which remains the primary characteristic of the LCAC.
With the shore-based defensive weapon systems available worldwide today, launching LCAC's up to 50 miles off shore proved to have obvious safety appeal for the US naval fleet. As the LCAC moves inland into a controlled staging area - supported by helicopters overhead - the enemy would shift its focus away from the fleet itself. A high-speed, over-the-beach craft able to make a possible tactical surprise with troops and material in tow and not exposing the fleet to enemy fire was the desired LCAC mission. Of course safety in any combat situation is impossible to control, however, and we have history to see the failings of amphibious assault craft in past wars.
The LCAC has a number of short comings; they are constructed of rubber and canvas with no armor protecting the crew or troops on board. A very large craft also provides for a very large radar image. Once on land her speed and maneuverability is greatly reduced down to 6 knots. The six gas turbines are noted as being very noisy and can be heard at a great distance. If damaged, LCACs have proven very difficult to tow and driving in reverse is taxing for the driver. Naval gunfire will be out of range to support the initial landing and the buildup of combat troops and material ashore will be slow due to the turnaround time for LCAC.
It is of note that the LCAC, and the men and women who will come to count on them, have not been tested in combat.