LCACs IN SUPPORT OF THE AMPHIBIOUS LANDING AUTHOR LTCMDR. Ronald L. Aasland, USN CSC 1991 SUBJECT AREA - Operations LCACs IN SUPPORT OF THE AMPHIBIOUS LANDING Over the past two centuries of the U.S. Marine Corps' existence, the military had witnessed a transformation of the Corps from a law enforcement and Naval base security role to an organization tacked with the vital role of projecting U.S. military power ashore through amphibious operations. This evolution occurred slowly until by 1929, "it was well established that the role of the Marine Corps was to provide a small well-trained amphibious assault force to seize and occupy bases for fleet operations." (8:28) Throughout World War II, the Marine Corps continued to refine its amphibious assault capabilities throughout the Pacific Island hopping campaign. All aspects of the amphibious assault were highly developed including the latest in assault and landing crafts. These crafts were capable of transporting troops and equipment ashore in sufficient numbers to constitute the strength required for offensive land operations. Although these crafts only moved at approximately eight knots, cruiser and battleship fire support, along with close air support, kept the enemy pinned down until the marines were established ashore. Since World War II, the advent of the helicopter added the dimension of vertical envelopment and sped up the pace for the buildup of power ashore. Unfortunately, assault and landing crafts continued to plod ashore at between eight and ten knots. Innovative development of surface crafts to keep pace with the helicopter did not happen until the Navy purchased its first six Landing Craft Air Cushion (LCAC) vehicles in 1986. With the LCAC racing ashore at 40+ knots, the Navy and Marine Corps both began reconsidering the concept of the Over- the-Horizon (OTH) assault. Now ainphibious assaults could be conducted in excess of 25 nautical miles from the beach and achieve tactical surprise and/or keep the amphibious task force out of the range of enemy coastal defensive weapons. (14:2) From the surface side of the amphibious assault picture, it looked as though the problem had been solved with regards to rapidly building up the landing force from over the horizon. Little did the Department of the Navy realize what budget cuts of the 1990's would do to this impressive surface assault platform. As the Marine Corps moves forward in implementing the Over-the Horizon amphibious assault, it will depend very heavily on the capatibility of the LCAC. With Department of Defense cutbacks in the procurement of amphibious ships and LCACs, the ability of a Marine Expeditionary Brigade (MEB) sized force to rapidly build its combat power ashore prior to an enemy counterattack is seriously in doubt. OUTLINE LCACs IN SUPPORT OF THE AMPHIBIOUS LANDING Thesis: As the Marine Corps moves forward in implementing the Over-the-Horizon (OTH) amphibious assault, it will depend very heavily on the capability of the LCAC. With Department of Defense cutbacks in procurement of amphibious ships and LCACs, the ability of the Marine Corps to rapidly buildup its combat power ashore prior to an enemy counterattack is seriously in doubt. Outline: I. Historical perspective. A. Development of early amphibious vechicles B. Development of early amphibious doctrine C. Pacific lessons learned D. Present application II. LCAC capabilities and limitations. A. Characteristics B. Capabilities C. Survivability D. Limitations III. The Over-the-Horizon Assault. A. LCAC cycle time B. MEB/LCAC composition C. Total lift requirements IV. Analysis. A. Lack of LCACs/LCAC capable ships B. MEB raid versus forcible entry EXECUTIVE SUMMARY LCACs IN SUPPORT OF THE AMPHIBIOUS LANDING Thesis: As the Marine Corps moves forward in implementing the Over-the-Horizon (OTH) amphibious assault, it will depend very heavily on the capability of the LCAC. With Department of Defense cutbacks in procurement of amphibious ships and LCACs, the ability of the Marine Corps to rapidly buildup its combat power ashore prior to an enemy counterattack is seriously in doubt. Issue: This paper presents an overview of the Landing Craft Air Cushion (LCAC) and its ability to support the amphibious surface assault. An historical review of amphibious vehicles and doctrine lays the foundation for the requirements of such a landing craft. An analysis of the LCAC's characteristics, capabilities, survivability, and limitations point out the utility and necessity of the LCAC in modern amphibious warfare. Due to Department of Defense cutbacks in procurement spending, the Navy has cut its total number of LCAC capable ships and overall LCAC program. This reduction in a program so increasingly vital to the amphibious surface assault force, seriously brings into question whether U.S. Naval forces will be capable of conducting forcible entry. Conclusion: Only the continued procurement of the LHD and LSD class ships along with the full complement of 104 originally planned LCACs will ensure the forcible entry capability of U.S. Naval amphibious forces. HISTORICAL PERSPECTIVE During the early stages of the development of amphibious doctrine, it was quickly recognized that the ship-to-shore movement was a particularly vulnerable time for the troops. Jeter Isely in his book on the historical and doctrinal developments of amphibious warfare writes, Therefore the main problem in planning a ship-to- shore movement is to get troops disembarked into their boats rapidly and in the right order, and to dispatch the landing craft to the beach as quickly as possible in formations that will reduce the danger of being hit. (8:42) Landing crafts were developed by several contractors, all of which exhibited some innovative concepts, but limited by technology could still do no more than eight knots. Most of the changes and advances in the amphibious warfare concept came from lessons learned during the World War II Pacific Island hopping campaign. With many of the islands and atolls surrounded by coral reefs, a craft was required which could both swim and climb over reefs, if required, in order to deliver its troops to the beach. The amphibian tractor, which had originally been intended chiefly for logistical employment, was adapted to become one of the most important tactical weapons of the war. Tarawa illustrated both the utility of these vehicles and the folly of not having them on hand in large numbers. Never again in the Pacific War were assault troops to be handicapped by serious shortages of this vital piece of equipment. Later the same machine was armored and armed with guns or howitzers and employed to lead the first waves of troops into the shore. (8:583) However, the most significant and decisive progress of amphibious warfare was in the field of naval gunfire support. This progress was achieved through the assimilation of lessons learned through the experience of assaulting well fortified and defended Japanese-held islands. At Okinawa... seven full days were allotted to naval bombardment before the day the first troops were put ashore on the main island of Ryukyus... Clearly by the end of the war it was recognized that in the absence of compelling reasons to the contrary, an extensive period of prelanding naval bombardment was one of the vital keys to amphibious success. Adoption of such measures meant the sacrifice of tactical and to a certain extent even strategical surprise. (8:588) Although telegraphing a proposed landing site to the defenders of an isolated island through extensive shore bombardment might be the prudent thing to do, it is questionable when confronting a well-defended continental land mass. Where the enemy has powerful forces distributed over an extensive area and a system of land communications capable of massing these forces rapidly in any desired spot, advanced warning of the location of the key beaches which the attackers intend to strike might well prove disastrous to assault. It is not difficult to imagine, for example, what would have happened to the attack forces at the Normandy beaches in June 1944 if a large naval task force had moved in several days before the initial landing was to be made, if it had commenced to shell the selected beaches and if the Germans had correctly estimated the situation. (8:598) From these lessons we can learn that a rapid transit for the troops during the ship-to-shore movement is essential to minimize their exposure to enemy fires. This transit must also be made in a landing craft capable of traversing obstacles on the way to the beach. Since extensive prebombardment of the shore may signal our intended landing site, the landing craft must be capable of surviving the initial assault on prepared and undefended beaches. As the OTH assault moves the amphibious task force further away from the beach, naval gunfire support ships can no longer provide essential shore prebombardment making it essential that assault craft be constructed to survive the initial assault. LCAC CAPABILITIES AND LIMITATIONS The advent of the LCAC in the amphibious force has added a new dimension to the surface assault. Besides operating at greater than four times the speed of conventional displacement hull craft it is also capable of crossing approximately 73 percent of the world's coastlines as compared to 17 percent for conventional crafts, greatly complicating a defender's task. Weighing 87 1/2 tons, it carries a standard 60-ton payload, or an overload 75-ton payload, on a cargo deck. Its gas turbine propulsion and air cushion technology allow it to travel at speeds in excess of 40 knots. This tremendous versatility allows it to move troops and all equipment in the current Marine Corps inventory. The LCAC employs hovercraf t technology to skim across the ocean surface on a cushion of air. It has a range of 200 nautical miles. With a full payload, it can travel at speeds in excess of 50 knots in sea state 2 and 40 knots in sea state 3. Overloaded, it will still achieve 50 knots in Sea state 2. Unconstrained by winds, tides, reefs, underwater obstacles, mines, beach gradient and beach traf f icability, the LCAC can cross the shore- line and proceed inland at speeds up to 35 knots. Ashore, it will cross 20-foot ditches and 5-foot vertical obstacles, knock down small trees, and climb gradients up to 13 percent. (1:75) Launched from 10-100 miles offshore, the amphibious task force can remain over the horizon, beyond the reach of shore- based target acquisition systems. With the deployment of LHA, LHD, and LSD-41 class amphibious ships, the aggregate numbers of LCACs in an amphibious task force continues to increase. For more technical data on the LCAC, see appendix A. Click here to view image This growing utilization and dependence of the Navy on the LCAC has forced both the Navy and the Marine Corps to reflect on the operational capabilities of these crafts. Faster than conventional landing craft, they now require their own landing beach during assault operations. Due to their range and speed, they can easily outrange the task force to conduct advance force operations or subsidiary operations. If an intended landing site is heavily defended, the LCAC can shift to an alternate site 10-15 miles away, allowing for buildup of the force in a relatively benign area. (4:43) As a large, heavy, air-cushion vehicle, the LCAC can launch in sea states prohibitive for LCM/LCU operations. The air-cushion buffering effect also provides a better ride than displacement hull craft in all weather. This is an essential concept when trying to land combat effective troops who have been in transit for 30 to 60 minutes. An LCAC's RADAR and navigation systems also allow for operations during adverse weather. Since the LCAC was designed for use in the OTH surface assault, it was realized that this craft would have to be capable of surviving the initial assault on defended beaches. The most vulnerable area of an LCAC is its drive train and exposed propulsion systems. (3:18) If it is known that a landing must be conducted against a heavily defended beach, an additional five tons of armor can be placed around the drive train system to enhance survivability. However, the addition of this armor has an impact on the handling and maneuverability of the LCAC as well as reducing the overall payload. Both bottom laid and deep water mines have always been a principle concern of landing craft. With the LCAC, the hull is protected by an air cushion which makes it virtually invulnerable to deep water mines. (4:43) As the LCAC moves into shallow water, its air cushion causes no pressure wave characteristic of displacement hull crafts. It is thus less vulnerable to shallow water bottom mines. Unless it suffers a detonation directly under the LCAC, "offboard detonations of shallow water mines and near-miss direct and indirect fires are not considered to be significant problems." (4:43) The "LCAC Survivability Study" conducted by the Center for Naval Analysis determined that approximately 40 percent of the air cushion's skirt could be destroyed and still maintain enough cushion for operation. (3:6) Another vulnerability study conducted independently by the Ballastic Research Labratory concluded, . . . that the LCAC was relatively invulnerable to small-arms fire and artillery fragments. The study also stated that only direct hits by large explosive warheads greater than 30 mm would pose a threat to the LCAC components. (12:77) Yet, despite the tremendous capability of the LCAC, there are some limitations and drawbacks to it use. Due to its size and the design limitations of the LHA, only one LCAC vice four LCUs can be transported by the LHA. This is a reduction in payload capability from 660 short tons to approximately 60 short tons, a tremendous loss in surface lift capability. The high profile of the LCAC also makes it a vulnerable target as it approaches the beach. The two very noticeable huge push propellers to the rear of the craft would be likely targets for shore defenders. Once damaged, the propulsion blades quickly disintegrate rendering the craft immobile. Four lift fans provide the air cushion the LCAC rides on. In the event these fans, the four Avco-Lycoming gas turbines, or any part of a series of eight separate gearboxes are damaged, a portion or all of the air cushion may be lost. (13:1-2 to 1-3) Without the air cushion and having no wheels, the LCAC is incapable of being towed. So even minor damage to a vital engineering component could quickly strand an LCAC on a hostile beach. The LCAC has provided some tremendous advantages to the surface lift and assault capability of the amphibious task force. Yet this design which provides enhanced survivability also inf licts additional vulnerabilities and limitations on the LCAC. THE OVER-THE-HORIZON ASSAULT The Department of the Navy's "Amphibious Lift/Aviation Requirements Study" of 1989, examined in detail the ability of the LCAC to support a MEB-sized force when landing against elements of a "classic" Soviet motorized rifle regiment (MRR). It was estimated that in a high threat environment the lead battalion of the MRR could engage within 90 minutes and that subsequent battalions would arrive at intervals of 90 minutes. This would result in full regimental strength between H+l80 to H+270. A mid threat environment would result in a closure rate of 90-110 minutes resulting in the MRR at full strength by H+27O to H+330. In a low threat environment, the MRR could achieve full strength in a least time of 330 minutes. (19:39) Furthermore, it was determined that 84 LCAC lifts were required to transport the surface assault components of the MEB. (19:38) Two thirds of the force participated in the surface assault while the remaining one third constituted the vertical assault force. The capability of all assets were utilized as fully as possible and cargo required in the initial assault was included with the vehicles in the standard loads. Assuming that the operation is to take place "over-the- horizon" to enhance survivability of the amphibious task force and minimize the possibility of detection, the initial assault was launched at 25 nautical miles from the beach. Subsequent operations were conducted from 20 nautical miles from the beach. Not until the beachhead was secure would the amphibious task force move to within sight of the beach. Allowing for an LCAC operational speed of 40 knots to and from-the beach, we can figure 68 minutes for transit. Five minutes are required for entering/exiting the well deck and two minutes for going on/off cushion and opening/closing the bow and stern ramps. (19:A-4.5) This gives us a cycle time of 75 minutes for the initial assault wave. Subsequent waves would operate from 20 nautical miles and require an additional l0 minutes to load and gripe vehicles to the LCAC. This would result in about a 78 minute cycle time for the second and subsequent assault waves. Now is we look at the Navy ships in a standard MEB-sized force we see that it normally consists of between 15 to 18 ships. A force consisting of 1 LCC, 1 LHD, 2 LHAs, 3 LPDs, 4 LSDs, and 4 LSTs would carry approximately 21 LCACs. The "Amphibious Lift/Aviation Requirements Study" point out that 18 LCACs are required to support the surface ship-to-shore movement in a low threat environment, 24 LCACs in a mid threat and 30 LCACs in a high threat environment. To lift even 24 LCACs would require 25 of the 30 amphibious ships assigned to the Second Fleet. (19:40) ANALYSIS A recent article in Navy Times points to the developing problem in supporting a MEB -sized force. Proposed budget cuts in the Department of Defense will terminate procurement of the LHDs one short of the anticipated five for its class, four short for the Whidbey Island class LSDs and hold LCACs to 64 vice 104. (17:8) This reduction in the procurement of LCACs and LCAC capable ships along with the scheduled decommissioning of the LPHs, LPDs, older class LSDs, and the LSTs will seriously degrade the Navy's ability to project amphibious power throughout the world. Through procurement reductions in amphibious ships and projected decommissions, we will be facing an amphibious force of 30 ships on the East coast. With 25 required to support a MEB-sized force there will only be five lift in Second Fleet for yard repairs, contingency/special operations and scheduled exercises/commitments This force of 25 ships will also strip away all of the LHD/LHAs and two thirds of the Whidbey Island class LSDs. Assuming that the 64 LCACs will be roughly split between the two coasts, we are only looking at a total of 32 LCACs on each coast upon completion of procurement at the end of FY 98. With some LCACs in maintenance cycles, damaged or being used on special operations, it will be difficult to pull together 24 LCACs to support a MEB. The "Ship-to-Shore Movement" analysis conducted by BDM Corporation concluded that LCACs would suffer a 30 percent attrition during an amphibious assault. (2:14) This subsequent loss of LCACs would have a tremendous impact in the ability of the surface force to carry out and continue its operations. Going back to our earlier analysis of LCAC cycle time, we can determine that provided 21 LCACs in our amphibious force, 75 to 78 minutes for cycle time and a requirement of 84 lifts, it will take 309 minutes to land our surface assault force. Our limitations allow us to reasonably counter a low threat situation, but not a medium or high threat Situation. This lack of required LCACs and LCAC capable ships gives us the ability to project our amphibious power against an unsophisticated, ill-defended opponent. The limitation of our LCAC supported surface force will be the execution of small raids or advanced force operations. In the face of a mid to high level threat, the surface force lacks the LCAC punch necessary to conduct a forcible entry. As the Marine Corps continues to move forward in its implementation of the over-the-horizon amphibious assault, it will depend ever increasingly on the capability of the LCAC. Unfortunately, with the Department of Defense's cutback in the procurement of LCAC capable amphibious ships and LCACs themselves, the ability of the Marine Corps to rapidly buildup its combat power ashore prior to an enemy counterattack remains seriously in doubt. If we are to maintain a credible amphibious assault force capable of forcible entry, we must continue with our original procurement plans to procure five LHAs, all of the LSDs and all 104 planned LCACs. BIBLIOGRAPHY 1. Bailey, Maj. Thomas A."Over-the-Horizon Assault by LCAC." Marine Corps Gazette, 101 (January 1986), 74-80. 2. BDM Corporation. "Mission Area Analysis of Mission Area 232.2, Ship-to-Shore Movement." Secret/NOFORN. 24 August 1987. 3. Center for Naval Analysis for the Department of the Navy. "LCAC Survivability Study." 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