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LPH-2 IWO JIMA class

The seven IWO Jima class amphibious assault ships were built to transport more than 1700 fully equipped Marine Assault Troops into combatr areas and land them by helocopter at designated inland points. This technique of vertical envelopment pioneered by the Navy-Marine Corps Team, exploits flexibility and suprise. The ships are capable of supporting a Marine Batallion Landing Team, it's armament, vehicles, equipment and a reinforced squadron of transport helicopters and various support personnel. Combat-ready Marinesare flown in-land behind the enemy's defenses by helicopters to isolate strategic strong points, disrupt communicatioins, and converge with beach landed Marines to gain ultimate control of their objective. The ships also supports mine-sweeping operations with Helicopter Mine Countermeasure Squadrons and provides humanitarian assistance and a non-combatant evacuations of American Embassy personnel and citizens caught in civil-conflict overseas. USS Guam (LPH-9), homeported at Norfolk, VA, was the last ship of this class in service. [Confusingly, the seven ships of this class were not sequentially numbered, with intervening numbers being assigned to ships of other classes converted to perform the amphibious assault mission].

The Marine Corps needed a ship designed and built from the keel up to provide for this third element, a ship in which the designers could provide for large troop spaces and cargo elevators right from the initial concept. Such a ship, in essence, would be built around the ship's crew, the helicopters, and the assault Marines. The first such vessel to be built was the USS Iwo Jima (LPH 2). The construction of this unique ship was authorized 27 January 1958 and her keel laid at the Puget Sound Naval Shipyard at Bremerton, Washington on 2 April 1959, just a year after General Pate had compared the lack of such ships to building Polaris missiles without providing submarines to launch them.

What was launched 17 September 1960 still looked from the outside somewhat like a conventional aircraft carrier. Only half as large as the Essex class conversions (with a full load displacement of 18,000 tons), Iwo Jima was only 592 feet in length, just barely longer than the Thetis Bay although with almost twice the "Teddy Bear's" displacement. This combination gave the Iwo Jima and the six almost identical ships that were to follow her none of the sleek lines of a fast warship. Instead, she was almost "plump" in her appearance, square sterned, with a short sharp bow that quickly flared out into her 84-foot beam and with a flight deck 52 feet above the water line that covered all but a very small portion of the entire outline of the ship. Inside her hull was what none of the conversions had, full provisions for all three elements of the amphibious assault team-the helicopters, the combat Marines, and the crew of the ship.

In the simplest terms, an LPH of the Iwo Jima class was not a single type ship. She was three completely different vessels stacked on top of each other. At the lowest level was what amounted to an attack cargo ship (AKA) with large holds to store the supplies and equipment of the assault Marines and two large cargo elevators that could bring the material up to either the hangar or flight decks for staging. Both areas were normally used. This storage area was supplemented by an area aft of the hangar deck in which combat vehicles could be carried. To expedite loading at a dock, the designers had included a ramp which could be attached to the aircraft elevators on the outside of the hull, allowing the jeeps and other vehicles to drive directly on to the ship and into the vehicle stowage area. The second layer of the Iwo Jima class extended from the holds up to the hangar deck and was equivalent to an amphibious assault transport (APA). In this section, and a few others scattered throughout the hull, were the large berthing and messing spaces required by 1,900 assault Marines and helicopter mechanics. Though hardly luxurious, these spaces did provide each Marine with a small metal locker to store personal items, separate storage rooms for his pack and rifle, and in the description of one observer who obviously had had experiences with older troop transports: "a comfortable bunk, complete with mattress." These two layers made the Iwo Jima class unique. The provisions for them was what had so seriously handicapped the conversions.

The final layer was more conventional and was what gave the ships their distinctive aircraft carrier-like appearance: the facilities for launching and recovering helicopters from the flight deck, storing them on the hangar deck, and the machine shops and work spaces for the mechanics to maintain the aircraft. To expedite the moving of helicopters from the flight deck to the hangar deck, two elevators, each with a capacity of over 17 tons (a fully loaded HR2S weighed slightly more than 15), were installed, not in the center of the flight deck as had been the case in World War II carriers, but on the outer edge of the flight deck where they operated up and down the outside of the hull. One was on the port side directly abeam the island superstructure; the other one was on the starboard directly aft of the island. To insure that the ships could traverse the Panama and other canals (for when both elevators were extended the ship had an extreme width of 105 feet), the elevators could be folded up along the side of the hull. In actual usage, these aircraft elevators performed an additional function. Cargo could be brought up from the hold to the hangar deck, staged there and moved aboard the lowered elevator. Then to rapidly bring large quantities up to the congested flight deck, the elevator was simply raised. This proved extremely effective, particularly if the cargo was to be carried externally by the helicopter. The same method was used to assemble large units of Marines on the flight deck, ready for boarding their aircraft. The individual teams would form up on the elevator from the hangar deck and with a blare of the klaxon horn, a slight jerk, they would be lifted up to the flight deck beside their waiting helicopters.

Smaller portions of other ships were included also. Above the vehicle stowage area was a hospital that could, in an emergency, accommodate more than 300 casualties (by utilizing the troop berthing space directly aft of it). This particular feature would take on increased importance as the LPHs responded to natural disasters and evacuation of civilians from troubled areas. The deck edge elevators could be utilized in just the reverse of their role in launching assault troops. The sick and wounded were unloaded directly from the helicopters onto one of them, dropped down to the hangar deck and moved to a waiting elevator which lifted them up one deck to a large door leading to the hospital. This fifth elevator, incidentally, was often loudly - and accurately - proclaimed as the only one in the entire ship specifically designed to move people.

In addition, each of the LPHs of this series had a complex communications center for the control of all the helicopters in the assault . Termed the HDC (for Helicopter Direction Center), it and a similar one for the control of supporting fires (FSCC), which were interconnected along with the ships own Combat Information Center (CIC), could act as the coordinating agency for a much larger assault with other ships and aircraft.

Though the LPHs to follow were almost identical, the Iwo Jima and several of her sister ships had provisions for another function: the offices and communications for both the amphibious force commander and the landing force commander. Ships so modified were tagged "flag configured."

Both as a matter of comfort for the crews and embarked Marines and to assist in maintaining structural strength in a ship that was such a hybrid, the entire vessel was air-conditioned. Popular legend had it that there were no port holes in the LPHs. There were, but what few of them existed were all high in the island structure, an area not normally visited by the assault Marines.

As if the combination of an APA, an AKA, and a helicopter aircraft carrier were not enough, the ship had a space for the crew of 50 officers and 500 Navy men to operate her. The design of such a ship was a remarkable achievement for all the engineers who visions for almost every conceivable situation from played a part. Into her stubby hull were crammed amphibious landing in an atomic age to peacetime disaster rescue missions and most assignments between those two extremes.

She was designed to be very versatile. To accomplish all of this, however, the designers had to make a few compromises. The ships had two separate boilers and associated engines but a single propeller. Such a design saved space for other functions (and was less expensive), though the 22,000 horsepower generated was enough to drive her through the water at a speed slightly in excess of 21 knots. This combination, coupled to the size and shape of the hull, led to some unexpected results.

One characteristic was first noticed shortly after the Iwo Jima left the dock on 5 September 1961 for her initial tests at sea. On board were Captain Thomas D. Harris, USN, the first naval officer ever to command a true LPH, his crew learning the intricacies of an entirely new breed of ship, and the officials and engineers from the Puget Sound Naval Shipyard, who had built her. The next day she returned to dock. Obviously such an innovative design was going to have a number of small discrepancies on her first shakedown. The Iwo Jima did. One of the most serious was described in the official reports as: "severe hull vibrations at high power." On 14 September once again she cast off, heading for sea. Most of the original difficulties had been corrected. The vibration persisted. A week later a third trip was made, this time as her official Builder's Sea Trials, a period of testing and exercising the ship to verify if she would perform as predicted." The hopes of the engineers were vindicated. She performed well. The only disappointment was that "the chief remaining discrepancy was (still) vibration at high power."

This characteristic vibration was never to be cured in any of the class. At about 15 knots the entire ship began to shake every time one of the blades of the screw took a bite of the water. At that speed it was slight throughout all the ship, but more pronounced in the stern and bow Marine berthing areas. As the speed increased, the vibration increased correspondingly in frequency and severity. Embarked Marines soon learned to recognize it and within a short period of time actually could tell how fast the ship was going by the rattle of the decks. It was as if the builders had given each man aboard the vessel his own private speedometer. As the Iwo Jima and her sister ships reached 21 knots the pounding became more pronounced and was inescapable anywhere on board.

To the builders this was " severe vibration at high power". To all Marines who experienced it, it was "the twenty-one knot thump." While on a peacetime deployment, if wakened by the thump in the middle of the night, the Marines knew that another crisis had occurred, that their ship was proceeding at maximum speed, and that the next morning could bring them into action. When the thump began, the ship would come strangely to life, unbidden. Marine officers would begin appearing at the HDC. Assault riflemen would be restless in their bunks and helicopter mechanics would begin worrying about some minor detail on their aircraft that they had postponed repairing . The designers had not intended it this way but they had given each Marine an unavoidable and unmistakable alarm system.

Designers of ships, much like airplanes, have complex formulas, even computers, to predict how an individual craft will perform. The variables are so great that it is impossible to predict with any absolute certainty. There is only one way to do it : take the ship to sea, or the aircraft into the air, to see if it will perform as expected. Considering the divergent demands that the engineers had to resolve, the Iwo Jima class LPH was a resounding success.

Deployed to the Persian Gulf as part of the military forces which ultimately would be used to drive Iraqi forces from Kuwait, on 30 October 1990 Iwo Jima (LPH 2) suffered a high-pressure steam leak that cost the lives of 10 of its crew, but repairs kept her fully operational. A steam turbine valve in the fireroom sustained a catastrophic mechanical failure. This failure resulted in the release of superheated steam at a temperature of 850 degrees Fahrenheit into the fireroom. The investigation determined the cause to be failure of the bonnet fasteners of a ship service turbine generator root valve. The valve had just been repaired by a shipyard where the bonnet fasteners were replaced with mismatched and incorrect material. The required fasteners were heat-treated steel studs and nuts. The fasteners installed during the maintenance were a mixture of bolts, studs and black oxide coated brass nuts. The high temperature and pressure placed on the fasteners during plant light off caused the brass nuts to fail catastrophically, which allowed the valve bonnet assembly to separate from the body. The replacement fasteners were furnished by Ship's Force, but no one (ship or shipyard) checked the fasteners, prior to installation, to ensure that the requirements of the technical manual and drawings were met. The Iwo was stricken in September 1995 and scrapped in Philadelphia, then towed upriver. The hulk was sold as scrap in August of 1996 for $140,000 to Mystic Shipping and Trading Co. and she was towed to New Orleans.

USS Inchon served as a key element of the US Naval Amphibious Forces 1970 to 1994 in both the Atlantic and Pacific Fleet. Inchon was converted from an amphibious assault ship to a dedicated command, control and support ship for mine countermeasures operations. The contract to convert Inchon was awarded in November 1994 to Ingalls Shipbuilding, Inc., Pascagoula, MS. USS Inchon was redesignated for its new mission on 24 May 1996 after undergoing a 15 month conversion and overhaul. Major changes were made to the Command, Control, Communications, Computers and Intelligence (C4I) system, with upgrades including the close-in weapons system (Phalanx) and various radars. The ship supports an embarked composite helicopter squadron of eight CH-53E and two SAR/spotter helicopters. It provides an alongside support, resupply and repair facility for up to four Avenger (MCM 1) Class mine countermeasures ships and Osprey (MHC 1) Class coastal minehunters. It can support and accommodate four Explosive Ordnance Disposal (EOD) groups with assigned equipment. Additionally it provides C4I facilities for the MCM group commander. New repair facilities and upgrades to older one were also added, giving the MSC 12 the ability to accomplish whatever repairs are necessary to weapons, LCACs, and aircraft in any theater of operation.

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Page last modified: 22-07-2011 17:39:57 ZULU