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LHA-1 Tarawa class Design

The Amphibious Assault Ships of the TARAWA class were the largest U.S. Navy ships of recent construction except for aircraft carriers and a series of oil-ammunition replenishment ships. The design of the LHA combined the experience and technology of 30 years of amphibious warfare since the first specialized ships for this purpose were constructed in the early 1940s. The large size and advanced features permit one LHA to perform the functions that previously required several different types of ships. Together with two of the NEWPORT class fast LSTs, one LHA can carry and land a full reinforced Marine battalion of some 1,800 men with all of their weapons, vehicles, and equipment, including tanks, trucks, and artillery.

The LHA resembles an aircraft carrier, having a large flight deck running the entire length of the ship with an "island" superstructure on the starboard side. This broad flight deck will permit the simultaneous operation of several helicopters. On top of the island structure are antennas for the various radars and radios in the ship, the bridges from which the ship is controlled, and directors for the ship's guns and missile launchers.

Immediately behind the island structure is a 60,000-pound capacity crane that can lift helicopters from a pier to the flight deck, or lift boats and landing craft from the flight deck to the water. Beneath the flight deck the hull of the LHA provides sufficient space to house some 2,800 sailors and Marines, providing them with all of the facilities of a small city; provide storage space for the guns, vehicles, and other equipment required by the Marines; the ship's engines and other machinery; a hangar for storing and maintaining helicopters; a dry dock that can be flooded to permit the LHA to carry and launch landing craft; and fuels for the ship, helicopters, and marine vehicles.

The Landing Helicopter Assault ship (LHA) bore little resemblance to the original LPH, the "Teddybear," USS Thetis Bay. At the time the true LPHs of the Iwo Jima class were being designed, the Marine Corps still had hopes of being able to conduct an " all helicopter" amphibious assault. Helicopter manufacturers continued to be optimistic that they could design and build a helicopter which could lift all the equipment needed for the attack. If this were to be the case, there would be no need for conventional landing craft and amphibious vehicles. Helicopters would carry everything. Thus the LPHs were designed with no provision for any landing boats, and the Landing Ship Dock (LSD), Landing Platform Dock (LPD), and Landing Ship Tank (LST) were built for surface attack.

The LSD and LPD were constructed with a "well deck." This ingenious arrangement allowed the ships to carry smaller landing craft inside them. When such a vessel reached its objective area, a large gate at its stern would be opened and, by taking on ballast, the ship would partially submerge, allowing the well deck to flood. The landing craft then could swim out and conduct the assault. On their return they could reenter the ship, the gate would be closed, ballast pumped out, and the well deck would once again be dry. It was an excellent system for surface assaults.

In the mid and late 1950s, the concept of an all-helicopter landing began to be questioned. The difficulties in producing the "Deuce" were a clear indication of the problems which would be encountered in any large helicopter. Attempts to reduce the weight of combat equipment to fit current aircraft were not all successful. There just seemed to be no lightweight substitute for some items, particularly tanks and heavy artillery. Thus the "all-helicopter" amphibious assault was set aside in favor of a balanced air and surface landing, which if not ideal, was obtainable. By now, the LPHs had been built and the lack of any facilities for landing craft was a matter of serious concern. In large-scale attacks, assault Marines often had to be transferred from the LPHs to the LSDs and LPDs to board landing craft. This posed constant problem s for commanders and reduced the inherent flexibility of a balanced amphibious attack.

These problems and the testing of solutions to them pointed to a need for a ship which had facilities for both helicopters and landing craft. The answer was the LHA. They combine a helicopter flight deck and hangar space with a well deck for landing craft. They were to be very different from the first conversion into an LPH. Where the "Teddybear" at a full load displaced 10,000 tons, the new models are four times as large, displacing 39,000 tons. The LHAs are larger even than the Boxer-class conversions. The flight decks are 820 feet long. Their beam of only 106 feet permits passage through the Panama Canal with a scant three feet to spare. Their tallest masts reach 221 feet above the keel, and are designed to fold so that the ships can pass under the Brooklyn Bridge, if it ever were necessary to do so.

If the "keel-up" LPHs were three ships stacked on top of each other, the LHA is at least five different ones. Large holds are included to handle essential cargo. There are living facilities for a total of 262 officers and 2,542 enlisted personnel, including 1,672 combat marines. The well deck can accommodate an assortment of landing craft and amphibian tractors. And, of course, there are spaces for the helicopters and the necessary spare parts and machinery.



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Page last modified: 07-07-2011 12:47:54 ZULU