Heavy Lift Landing Craft Air Cushioned (HLCAC)

In FY2005, Research and Development was slated to commence for the Heavy Lift LCAC Program. The craft was planned to have twice the payload of the current LCAC and be approximately 1/3 longer. The first Heavy Lift LCAC was planned for procurement in FY2009. Instead, work on the HLCAC was terminated, and work began in 2005 on the LCAC(X) LCAC Replacement Tactical Assault Connector, with the first craft IOC projected for FY 2014.

The 2003 Navy Transformation Roadmap noted that replacements for both the Landing Craft Air Cushion and traditional lighters, such as the LCAC-R and LCU-R, would provide the ability to combine high speed vertical lift operations with the heavy combat power and sustainment available for delivery via surface means. This document projected funding for the Heavy Lift LCAC (HLLCAC) begining in FY 2005. It noted that R&D in this area includes the Heavy Lift LCAC (HLLCAC) program, with the ExLog investment focused on the development of high lift propulsion fans and high volume lift fans. The Roadmap stated that HLLCAC would provide increased rapid amphibious transport across a broader variety of terrain, proliferating support options and increasing the throughput of equipment and assault forces to tactical positions. The Roadmap also stated that precision navigation is key to forcible entry operations in the 2010-2015 time frame for various amphibious delivery platforms such as the LCAC(X), LCU(R), and Expeditionary Fighting Vehicle (EFV).

Heavy Lift LCAC was a new start program in 2004, focused on resolution of technical design issues to support the development of a Heavy Lift LCAC variant resulting in a 50% increase in craft length over the standard LCAC to a LOA of 112 feet. It included development of propellers, shrouds, gearboxes and lift fans to support the additional craft propulsion requirements will be required. Commonality with LCAC components would be maximized consistent with maintaining acceptable design margins given the additional requirements.

The Navy studied the feasibility of developing a Heavy Lift LCAC (HLCAC) as a follow-on replacement for the LCAC SLEP. The proposed craft would increase in both length and cargo area - by 33% - over the present LCAC and would have double the payload (144 tons). The HLCAC would be capable of carrying two M1A1 tanks or 10 light armored vehicles (LAV).

The area of Joint Logistics Over The Shore (JLOTS) has received renewed emphasis over the past several years. The Army and Naval Services and each of the five regional Commanders in Chief (CINCs) have stated requirements for LOTS or JLOTS operations in time of conflict. The current version of air- cushioned craft, the LCAC, is most suited for LOTS or JLOTS operations conducted inside 10 nautical miles from shore. The proposed Heavy Lift Landing Craft, Air Cushioned (HLLCAC) would be better employed with the Amphibious Task Force beyond that distance.

The Seabase to Shore Surface Craft [SSSC] product line addresses new Marine Corps doctrine on pre-positioned support. Although the concept of Expeditionary Maneuver Warfare would have no beach support area as currently envisioned, moving all supplies from ships 25 or more miles offshore directly to units well inland will not always be necessary or possible. The 12-knot utility craft (LCU 1600) now carried with amphibious ships will be of limited support. Using efficient watercraft transportation to establish small, perhaps temporary, re-supply points along the shore could greatly reduce the burden on primary air transport. The ship-to-beach transport burden will fall on LCACs, with their 60-ton payloads and 25 to 40 knot speed.

The Seabase to Shore Surface Craft (SSSC) product line is in a state of transition. It had previously been focused on enabling the Heavy Lift Landing Craft Air Cushion (HLCAC). However, with the evolving doctrine in Expeditionary Maneuver Warfare and Seabasing, as of 2005 the Navy was reevaluating the HLCAC program. The ExLog FNC has successfully completed the model-scale evaluation of the technologies and is standing down its collaborative efforts with PMS377 to build, install, and test full-scale equipment on an existing LCAC.

Also as a result of the evolving concepts and doctrine, the Navy has identified other areas in which Science and Technology (S&T) investment is needed related to the transport of personnel, equipment, and material to, from, and between platforms in the sea base. Areas of interest include technologies for High Speed Sealift, Heavy Air Lift, and Beachable High Speed Connectors. The ExLog FNC is currently reviewing prior studies, performing necessary analyses, and planning programs to address technology gaps in all these areas.

The SSSC product line is also supporting STTR programs associated with the Seabase to Shore Surface Craft product line. One STTR addresses the development of improved self-contained actuators (both linear and rotary configurations). These programs are investigating the use of electro-mechanical, electro-hydrostatic, and smart material technologies to improve actuator performance and reliability, as well as the use of switched-reluctance and electric servo motors to eliminate problematic hydraulic systems. Additional STTR programs are being supported in an effort to improve existing cargo restraint technology and impact tolerant lightweight hull structural materials technology.

Rapid ship-to-shore transport can currently be achieved with existing LCACs, and their over-the-ground hovering performance characteristics are ideal for supporting limited inland operations. The 72-ton payload capacity of the current LCACs may limit their use for future seabasing operations. Therefore, enhanced versions of this craft have been proposed. Feasibility studies had identified a Heavy Landing Craft Air Cushion (HLCAC) vessel that has double the payload capacity and double the operating range of the current LCAC, while maintaining the 25 to 50 knot craft speed capability. The proposed HLCAC vessels would be approximately 42 percent longer than the current LCAC craft, but would maintain the same height and width dimensions in order to conform to existing well deck operations.

An SSSC technology roadmap analysis concluded that considerable advances in lift fan and propulsor technologies would be needed in order to achieve the lift and thrust levels required for the proposed HLCAC performance. To this end, the SSSC product line has supported the development of the technologies related to the design of these highly loaded lift fan and propulsor systems. Sub-scale model tests of the lift-fan and propulsor systems were conducted to evaluate system performance, and originally, future plans included the full-scale fabrication of each system using modern, light weight materials that exhibited improved erosion capabilities. These full-scale demonstrators were to be installed on an existing LCAC platform so that the at-sea performance of each system could be assessed.

The propulsor design is a critical enabling technology needed for the HLCAC program. The core HLCAC propulsor S&T issues are the ability to design and implement an advanced propulsor that will provide the thrust needed by the HLCAC and still operate within well-deck geometry constraints. Because scale effects will not support a direct extrapolation of the sub-scale test data to full-scale propulsor performance predictions, the tests reported here were used to validate the design tools used to develop the HLCAC propulsor design. To the extent the propulsor design tools are validated by these tests, the designs developed with the validated tools might be considered validated. The 2003 wind tunnel tests generally validated the tools used to design the HLCAC propulsor. For example, the predicted and measured model propulsor thrust agreed to within ±4%. In some instances there were differences between the design tool predictions and the experimental results. For example, the design predictions generally tended to over-predict torque by approximately 8%. Also, the design predictions that the propellers would be entering a stalled state at a blade angle of 40o and a yaw angle of 10o, was not evidenced by the wind tunnel tests.

The available level of funding did not support the design of a new craft to meet all stated needs, the goal of this product line is to develop products that can enhance the usage of today's lighterage for the stated mission. It appears that an updated LCAC or a modular lighterage system already under development will be engineered to meet these requirements.

The SSSC product line started with the development of a technology roadmap that has lead to a focus on developing propulsion technologies, cargo stabilization technologies, advanced hull-form technologies, and other technologies needed for craft-to-ship interfaces. The plan was focused on the propulsion and lift systems for the planned Heavy Lift Landing Craft Air Cushioned (HLCAC) initially, with planned product transitions in FY04-07.

By 2004 the lack of a viable transition/acquisition program has put a hold on the development of the full-scale lift fan and propulsor system demonstrators. The successful technology developed under the SSSC program, however, may be suitable to be leveraged to support the operation of future seabase connector concepts which may incorporate lift fan technology.