The Navy’s Noisy Invasion Force : Military: Definitely not stealth class, the Hovercraft nonetheless has proved its worth in difficult beach landings. Twenty of them train together at Camp Pendleton.

Navy Capt. Hank Howe labeled it “Hovercraft central.”

This was no ordinary exercise. The noise was deafening, the dust clouds immense. These 20 Hovercraft, or LCAC (landing craft, air cushion) were the largest number to fly in formation at one time anywhere in the world. Tuesday’s maneuvers were practice, Howe said, but “important practice” for any future military crises similar to those in Somalia and the Persian Gulf.

The 7-year-old Hovercraft--35 of them at Camp Pendleton, with 35 more in Little Creek, Va.--were deployed in Somalia and the Persian Gulf and, in Howe’s view, played indispensable roles in both places.

Their primary contribution: giving the United States an “over the horizon” invasion force in which each Hovercraft can deliver 75 tons of personnel and materiel from a minimum of 35 miles offshore and reach a beach within minutes at a speed of 35 knots. Their maximum range is 200 miles offshore, and the huge vehicles can travel over hilly terrain at 25 m.p.h.

“In a nutshell,” Howe said, “they expand the number of beaches we can hit, allowing us to go farther and deeper inland from the cushion of an over-the-horizon offshore location.”

Each vessel is 47 feet wide and 87 feet long, a flat, rectangular, amphibious assault vehicle that, in Howe’s words, is akin to flying “a bar of soap.” The craft is powered by six gas turbine engines that stretch the decibel level to an eardrum’s limit.

Crew members wore earplugs Tuesday, and those with contact lenses strapped on goggles to fight off the dust clouds created by an armada of LCACs from ACU-5, otherwise known as Assault Craft Unit headquarters at Camp Pendleton.

“We love acronyms,” Howe said.

Howe also loves Hovercraft, which arms experts say can cover 70% of the world’s coastal areas, compared to the 17% its predecessors could handle.

The units cost $22 million each and are manufactured by two New Orleans firms, Textron Marine Systems and Avondale Golf Marine. While at sea, they are stored, not on aircraft carriers, but on amphibious vessels that carry what is known as a “wet well.”

Navy officials say no Hovercraft have been damaged so far, but then none has encountered an open conflict, even during Operation Desert Storm. The United States uses them primarily to move massive amounts of military equipment from sea to land, although each can carry 23 combat-ready Marines.

“With the weapons capabilities other countries have, the over-the-horizon factor is the strongest attribute,” Howe said. “By launching 35 miles offshore, that’s an enormous arc for anyone to defend against.”

No other country has a craft quite like the U.S.-made LCAC, Howe said. But Japan is about to purchase two from the United States with delivery scheduled for 1997. North Korea and Russia have similar craft, but in his words, they “don’t compare.”

Some of the Pendleton-based LCACs are now deployed, with four due to return Thursday. Two are in Sasebo, Japan, near the North Korean coast, four are in the Indian Ocean and one is in Guam.

Navy Lt. Scott Davies, 28, is a veteran of Hovercraft deployments, having used them in Somalia from October, 1993, to February, 1994.

“We went to six different landing sites,” Davies said. “Most displacement vessels were incapable of landing because of low tides and sandbars. The LCAC were able to land in Somalia, cross through sand--it’s extremely soft there--and move up to a hard, packed road within minutes.”

The sensation of riding one, Davies said, is akin to flying, “especially when you’re over land, since no part of the craft ever touches ground. The bottom of the skirt is two to three inches off the ground, while the bottom of the hull is four feet off the ground. The skirt entraps the air, which gives you the lift.”