by Tom Clancy
The amphibious equivalent of a delivery truck is the landing craft. As noted earlier, the development of landing craft during World War II was one of the key technologies that made amphibious warfare possible. Today, the Navy's landing craft range from the high-tech LCAC (Landing Craft, Air Cushioned) to conventional Landing Craft, Utility (LCU) and Landing Craft, Medium (LCM). While older craft are on their way out, they still provide amphibious planners with a range of delivery options. This is critical as the Navy and Marine Corps wait for long-delayed systems like the AAAV and MV-22B Osprey to enter service in the early 21st Century. The older landing craft provide vital support to Maritime Prepositioning Force (MPF) units for contingency and follow-on forces. Let's take a look at these delivery vans. Other than the Marines themselves, nothing is closer to the tip of the amphibious spear.
Landing Craft, Air Cushioned (LCAC)
When you first see one on its concrete pad at Little Creek, Virginia, it looks like a pile of Leggo blocks on a flattened inner tube. It is hard to believe that such an odd machine changed the face of amphibious warfare. When they first appeared in the late 1930s, landing craft were never called "revolutionary" or "world shaking." But the Navy's introduction of the Landing Craft, Air Cushioned (LCAC) in the 1980s produced the biggest change in amphibious doctrine since the helicopter thirty years earlier. Pretty impressive for something that looks like a prop from a low-budget science fiction movie. Let's look LCAC over, and see for ourselves.
Landing Craft, Air Cushioned (LCACs) of Amphibious Craft Unit Four (ACU-4) operate during a 26th MEU (SOC) exercise in Tunisia in 1995.
OFFICIAL U.S. MARINE CORPS PHOTO
Amphibious planners always want to carry more payload, farther and faster. They dream of assault craft that don't need pleasant stretches of gently graded beach for landing zones. Conventional landing craft are limited to landing under optimal tidal and beach conditions--which means they have access to only 17% of the world's coastline. Traditional flat-bottomed assault boats severely restrict a planner's options. What was needed was new technology that did not require pushing a boxy hull through the water. The requirement was for a magic carpet, to whisk a seventy-ton battle tank across the water to the beach, and even inland.
The solution they found was a surface-effect vehicle: the hovercraft. A hovercraft floats on a cushion of air contained by a rubber skirt. Like a puck in an air hockey game, it barely touches the surface, but "floats" on the boundary interface. Riding a virtually frictionless layer of air, it needs relatively little thrust to move and maneuver. Hovercraft have great agility and speed, and they can carry a good payload with efficiency and economy. They are also relatively immune to rough weather and high seas. And they transition easily from water to ground, allowing the same craft to transport payloads some distance inland. Civilian hovercraft serve as high-speed ferryboats across the English Channel, and between Hong Kong and Macao in the Far East.
The Soviet Union, with its poor road network and vast marshlands, led the world in developing and deploying military hovercraft. During the Cold War, it built several types of amphibious assault hovercraft for the Northern, Baltic, and Black Sea fleets. Their planned targets were rocky coasts where conventional landing craft have little or no utility. But with hovercraft able to cross something like 70% of the worlds coastlines (versus 17% for conventional landing craft), they became a natural choice for Soviet Naval Infantry. Large troop- and vehicle-carrying hovercraft, known by NATO reporting names like Aist ("Stork"), Lebed ("Swan"), and Pomornik ("Skua"), could reach speeds up to 70 kt/128 kph, carrying heavy tanks, artillery, and troops. Technical intelligence reports made Western military forces sit up and take notice.
Early Western hovercraft were smaller, like the British-designed SR.N5 (called the PACV-series, when built by Bell for U.S. service), carrying an infantry squad or platoon. Field trials included combat deployments to Vietnam and Malaysia, with mixed results. The plus side was their speed and agility across rivers, swamps, and bays. The downside was vulnerability, especially their rubber skirts and propulsion systems. Despite this, Great Britain and Iran (under the last Shah) purchased many patrol hovercraft. Several factors kept hovercraft from entering Navy service as quickly--mainly money. The war in Vietnam was a huge financial drain in the 1960s and 1970s. The Navy and Marine Corps only began developing an amphibious hovercraft in the 1970s.
In late 1976 the Navy formalized a requirement and opened the competition for a Landing Craft, Air Cushioned (LCAC). Two contractors, Aerojet-General and Bell Aerospace (now Bell-Textron Land-Marine Systems in New Orleans, Louisiana), designed and built prototypes in the hope of winning a production contract for a planned fleet of over one hundred LCACs. The requirement included specifications for payload (up to 150,000 1b/68,182 kg), speed (greater than 50 kt/ 91 kph), and range (up to 200 nm/365 km at cruising speed). The Aerojet-General prototype was called JEFF-A; the Bell entry was JEFF-B. They looked similar when placed side by side. The competition was fierce, with both designs showing advantages and faults. In the end, Bell's JEFF-B design won, entering production as the Navy's new LCAC. JEFF-B's shorter length (87 ft/26.5 m versus 100 ft/30.5 m for the JEFF-A) and lower displacement (160 tons versus 162.5 tons) were decisive factors. In 1982, the Navy issued the first production contract for three LCACs. First delivery came in 1984, followed by ship compatibility trials. Lockheed Shipbuilding (later acquired by Avondale Shipbuilding) was certified as a second-source contractor, but Bell-Textron has built the majority of the craft.
By the late 1980s, several dozen LCACs were in service with the Navy, aboard a dozen amphibious ships in the Pacific and Atlantic fleets. Seventeen LCACs served on six LSDs during Desert Shield and Desert Storm, providing much of the lift during those operations. Though they did not conduct any assault landings, the amphibious forces offshore tied down over seven Iraqi divisions in coastal defenses around Kuwait City. The LCACs maintained a 100% availability rate throughout nine months of operations in the Persian Gulf, giving ARG commanders great confidence in their reliability. Since that time, the fleet has shifted the bulk of landing craft duty to the LCACs. In humanitarian and peacekeeping operations in Bangladesh, Haiti, and Somalia, and regular operations in ARGs, the LCACs again proved their worth. The total force of 91 LCACs was nearly complete by early 1996. More were planned, but the Navy's drawdown cut the original target of 107 units. The force of 91 LCACs is a national treasure which is being used hard.
To understand the LCACs, you need to visit one of two bases constructed to service them. I visited the LCAC facility at the Naval Amphibious Base at Little Creek, near Norfolk, Virginia. This is the home of Assault Craft Unit (ACU) 4, the core unit for Atlantic Fleet-based LCACs. A similar facility services ACU 5 (the Pacific Fleet unit) at Camp Pendleton, California. ACU 4 operates roughly forty LCACs, providing detachments of hovercraft to Atlantic Fleet amphibious ships. The size of these detachments varies according to ship type. The following table summarizes the LCAC capacity of various ships:
Given the mix of ships within an ARG, a MEU (SOC) commander might have between six and nine LCACs in his well decks. That is a lot of capability to project Marines and firepower in just a few small packages. The ARG commander must manage this handful of LCACs carefully.
As you walk up to an LCAC on the ramp at Little Creek, the first thing you notice is that it looks much more like an aircraft or spacecraft than a warship. Much of the design for the LCAC was based on aircraft structures and technology to reduce weight and maximize payload. The LCAC is basically a platform with lift fans underneath, and twin deckhouses and engines along the sides. There are ramps at both ends, and a large rubber skirt running around the sides. Most of the structure is aluminum alloy, with some ceramic splinter armor. LCAC has to be able to survive hits when it works inshore. The threats range from artillery to anti-tank guided missiles. The four Avco-Lycoming TF-40B gas-turbine power plants provide a total of 12,444 shp/11,800 kw, and are mounted in pairs. Two engines drive the fou
r 5.25-ft/1.6-m-diameter lift fans. The other pair drive the two 11.75-ft/3.6-m-diameter propulsion fans. Steering is done with variable-pitch propellers, aerodynamic rudders, and a pair of rotatable bow thruster nozzles. With a nominal load of fuel and a sixty-ton payload, LCAC can sustain up to 50 kt/91 kph in seastate 2 (a light chop) for a range of up to 328 nm/607 km. By cutting the payload, longer ranges can be obtained.
As you walk up the bow ramp, you enter a large (67-by-27-ft/20.4-by-8.2 m) cargo stowage area. Cargo tie-down points stud the decking, and there is a decided "crown" (or hump) to the deck to drain off any seawater. A nominal load of 119,980 1b/54,421 kg can be spread over 1,809.5 ft2/168.1 m2 of space. If necessary, this can be raised to an overload of 149,978 lb/68,027 kg as long as the seastate is moderate (the pounding of the waves in a high seastate can cause structural damage). Along with the deck cargo, there is room in the deckhouses for twenty-three passengers. Passenger accommodations are decidedly austere and very noisy when the LCAC is underway.
On the starboard side is the control cab, where the crew of five is located. This includes the LCAC commander, pilot, engineer, and navigator. U.S. Navy landing craft are commanded by a chief petty officer instead of a commissioned officer. This tends to make life aboard the landing craft a bit more relaxed and earthy than what you find aboard large amphibs; but don't think the enlisted crews of landing craft are lax about their responsibilities. On the contrary, they are highly professional, and over the last five decades, have won their share of Medals of Honor and Navy Crosses. Accommodations on the LCACs are spartan, with few of the "homey" amenities that we would find in the LCUs. Crews live on-board the ships where they are based, since LCACs lack galley and berthing facilities.
The control cab is laid out like an aircraft cockpit, which makes sense when you consider that an LCAC is more an aircraft than a surface craft. In fact, LCAC missions are listed on the daily ARG/MEU (SOC) air tasking order, to avoid interference with flight operations by helicopters and V/STOL aircraft. The control stations for the navigator, engineer, and pilot are laid out left to right. In addition to the throttle controls for the four TF-40B gas-turbine engines, there is a helm control station with instruments to assist in steering and navigation. These include a modified LN-66 navigation radar (to detect surface targets and land masses); an inertial system, known as the Attitude Heading and Reference Unit (AHRU); and a speedometer known as the High-Speed Velocity Log (HSVL). Like the Doppler sensing systems used on helicopters, described in Armored Cav, these sensors determine position, heading, and speed. A GPS receiver feeds into both the AHRU and HSVL systems, which makes pinpoint, split-second accurate landing possible for the first time. Now, all of this data is worthless if you cannot share it over a secure and robust communications system. The LCACs are fitted with a variety of VHF, UHF/VHF, HF, and FM transceivers, ranging from Motorola "Handy-Talkies" to fully encrypted digital radio systems.
The LCAC's role makes good communications a mission-critical feature. The LCAC is much faster than any previous landing craft. Speeds of up to 50+ kt/91 + kph are common, depending on load and seastate. This capability means that the big amphibious ships that operate LCACs no longer need to stand a few thousand yards/meters off of an enemy coastline, vulnerable to enemy fire. In fact, LCAC-EQUIPPED ships can stay up to 50 nm/91 km offshore and still be able to put a wave of loaded LCACs onto a beach every three hours. This three-hour cycle time is the normal turnaround used by Navy and Marine planners in landing operations. It assumes an hour each way for transit time, plus a half hour on each end for loading and unloading. This is what "standoff" really means, and LCAC is the first of three new systems (LCAC, the MV-22B, and the AAAV) that makes standoff amphibious assault possible.
You may wonder why so many navigational systems are necessary. If you have ever tried to navigate a boat 50 nm/91 km offshore, you would understand! As you approach a coastline, the reference points you use to determine your course and position are slow to appear, and even easier to miss. Now add in fog, rain, spray, darkness, currents, and uncharted rocks. Getting lost at sea is easy! History is replete with stories of amphibious landings which hit the wrong beach, even when the right one was in sight from the amphibious ships a few thousand yards away. Now, just imagine what kinds of errors are possible from 50 nm/91 km out!
The GPS receiver, with positional accuracy of a few yards/meters and timing accuracy within milliseconds, is the most valuable navigational system for keeping LCAC on course and on time. But a new system is coming on-line to assist that. Known as the Amphibious Assault Direction System (AN/KSQ-1), it ties every ship, aircraft, and landing craft in an ARG/MEU (SOC) into a common network, feeding positional data from each unit's onboard GPS system. This lets the LFOC and CIC monitor real-time positional, heading, and velocity information on every friendly unit in the area. This system should eliminate many of the coordination problems inherent to amphibious operations.
Riding aboard an LCAC is different from any other boating experience you will ever have. First, the entire LCAC is buttoned up and the bow and stern ramps raised. When the turbine engines start, the noise is tremendous, and safety rules prohibit any exposed personnel on deck during transit. Even inside the deckhouses, earplugs and/or hearing protection is a necessity to make the turbine whine endurable. To back out of the well deck of a ship like Wasp or Whidbey Island, the pilot reverses the forward maneuvering thrustors to ease out. One advantage of the LCAC over conventional landing craft like the LCU or LCM is that the mother ship's well deck does not have to be "flooded down." Because of their ability to "climb" over obstacles up to 4 ft/ 1.2 m high, the LCAC can easily cross the lowered stern gate of an LHD, LHA, LSD, or LPD, simplifying operations for the ship's crew. This also reduces the seawater spray thrown up by the LCACs. This salt spray gets into nooks and crannies in the well deck overheads, causing corrosion that requires a lot of labor to repair. In fact, NAVSEA has plans for future dockships with "dry" well decks specifically designed for LCAC-type landing craft. Meanwhile, the Navy is experimenting with new-corrosion control techniques, including flame-sprayed coatings to prevent rust.
Once clear of the well deck, the pilot usually takes the craft to a holding/ assembly area where it waits for any other LCACs being launched. If necessary in a "hot" area, the LCAC(s) pick up an escort of AH-1W Cobra attack helicopters. Now the pilot turns the LCAC to its desired heading, and takes off. The acceleration is smooth and rapid, and you have the feeling of riding on a magic carpet, or perhaps a really fast vacuum cleaner! While there is a fair amount of vibration, it is not the pounding that you feel in a conventional landing craft on a rough sea. The lift air flowing under the skirt tends to smooth out the wave action, making transits under all but the worst conditions quite tolerable. Speeds of 40 to 50 kt/73.2 to 91.4 kph can easily be maintained except for handing a maximum (sixty-ton-plus) load in heavy seas. For the pilot, the LCAC is easy to handle, though it tends to sideslip in a hard turn. This is because there is no keel or rudder to "bite" into the water to hold it steady. The LCAC is actually "flying" above the water, and the sensation is not unlike riding in a low-flying helicopter. The LCAC is quite maneuverable at all speed ranges. And it is stable and easy to handle, even at slow speeds in confined areas like a well deck or narrow rivers or swamps.
During transit, the navigator constantly passes course corrections and speed recommendations to the pilot, so that they will hit the target area accurately and on time. This notion that a landing craft can transit 50 nm/91 km or more and arrive on time at a pre-planned point is still a source of wonder to old amphibious warfare veterans. In fact, as noted earlier, the ability of beachmasters of the Navy's beach control teams to receive troops, vehicles, and cargo has not kept up with the ability of ships to off-load them, even from over the horizon. Even the introduction of computerized bar-code tracking linked to satellite communication systems has not solved the traffic jams that develop on a busy beach. This is one reason why LCACs don't always stop at the surf-l
ine to dump their cargo. The LCAC's capability to transit from water to land, and continue inland for a distance, is still being explored. For example, with a pre-surveyed GPS navigational point, an LCAC might unload an artillery battery several thousand yards/meters inland, far away from the maddening traffic jam of the beach. Such concepts are being integrated into the doctrine of Marine amphibious units right now.
As you approach the shoreline, the beach comes up fast, and there is the feeling of an impending crash into a oncoming wall. Then the pilot begins to retard the throttles a bit and decides where to transit onto the beach. In fact, when you actually "hit" dry land, the feeling is like going up the ramp of a parking garage. The pilot then follows the instructions of the beach control party on where to stop and unload. The lift fans are killed, the skirt deflates, and the LCAC is ready to disembark its cargo. Once the bow and/or stern ramps are lowered, vehicles and troops can off-load in just a minute or two. For palletized cargo or containers, it takes a bit longer, as a forklift or palletized lifter vehicle is needed to unload the cargo deck. Unloading completed, the crew buttons up, fires up the engines, and heads back to the mother ship for another load. In the case of a LHD or LSD where two or more LCAC may be vying for space in a well deck, the craft are parked nose to tail. Then, with the bow and stern ramps lowered, vehicles drive through one LCACs to reach the other one.
