OBJECTIVE: Develop a lightweight, corrosion-resistant, durable Foreign Object Debris (FOD) screen to protect Air Cushion Vehicle (ACV) propulsors from impacts or ingestion of FOD.

 

DESCRIPTION: The Ship-to-Shore Connector (SSC) is an Air Cushion Vehicle (ACV), or �hovercraft�, providing amphibious transportation of equipment and personnel from ship-to-shore and shore-to-shore. Foreign Object Debris (FOD) screens are on every Navy platform that uses gas turbines (from airplanes and helicopters to ships). FOD screens provide critical protection to the machinery aboard the host platform and are subject to corrosion inducing harsh environments. This is especially true on an ACV, which operates in environments that include constant vibrations, impacts, high winds, salt water, and sand. Current FOD screens are made of expensive to procure and maintain stainless steel, weigh 238.81kg, and are prone to corrosion. ACVs would benefit from a corrosion resistant FOD screen that reduces weight by at least 10%. A 10% weight reduction would result in an increased payload capacity. An optimized FOD screen design adhering to the requirements listed below would allow for increased payload and fuel efficiency due to any amount of weight savings and a reduction in maintenance due to increased corrosion resistance. A more durable FOD screen will result in lowered overall maintenance cost. An improved FOD screen will enable the SSC to meet protection requirements while adhering to unblocked flow requirements as stated below.

 

Development of a corrosion-resistant, robust, maintainable, lightweight (215 Kilograms or less) FOD screen is paramount to improved SSC operation through protection of the propulsors from impact or FOD ingestion. The craft contains two propulsors approximately 4 meters in diameter consisting of a shroud, stators, and 6-bladed variable pitch propeller. The shroud will have nine equally spaced clevis and pin attachment points on the outside surface to mount the FOD screen. The FOD screen should protect the propeller, the stator, and the shroud�s leading edge from ingested objects greater than or equal to 100 mm in diameter with kinetic energy up to 2800 newton meter (Nm) and objects with an impact area of 1.5 m2 or less and kinetic energy up to 5000 Nm. The FOD screen must have an open (unblocked) area of no less than 1.54 x 107 mm2.

 

PHASE I: Develop a concept for a FOD screen for an SSC that meets the requirements in the Description. Demonstrate the feasibility of the concept in meeting Navy needs by material testing and analytical modeling. Develop a Phase II plan. The Phase I Option, if exercised, should include the initial layout and capabilities to build the prototype in Phase II.

 

PHASE II: Develop and deliver a prototype FOD screen that meets the requirements in the Description. Install the prototype on an ACV or appropriate test platform for durability and impact testing. Test and evaluate the prototype to determine its compatibility with current craft layout and ability to perform to requirements. Use the evaluation results to refine the prototype into a design that will meet the SSC Craft Specifications. Refine the design of the FOD screen based on Phase II testing, and prepare for Low Rate Initial Production (LRIP). Prepare a Phase III development plan and cost analysis to transition the technology to Navy use.

 

PHASE III DUAL USE APPLICATIONS: Support the Navy in transitioning the durable FOD screen for Navy use on the ACV program.

 

The SSC durable FOD screen will have private sector commercial potential for hovercrafts of this scale operating in the near-shore or on-shore environment that currently use expensive to procure and maintain stainless-steel designs. Commercial applications include ferries, the oil and mineral industry, and cold climate research and exploration.

Other industrial or military machinery with high airflow and rotating machinery could also benefit from technologies developed during this effort.

 

REFERENCES:

1.   Connors, H. and Murphy, J. "Gas Turbine Sand and Dust Effects and Protection Methods." SAE Technical Paper 700705, 1970. https://doi.org/10.4271/700705

 

2.   Filho, Jo�o Batista Pessoa Falc�o and Silva, Layra Mendon�a. �Design of a Foreign Object Damage (FOD) Screen and Analysis of the Impact Caused in a Transonic Wind Tunnel Performance.� 15th Brazilian Congress of Thermal Sciences and Engineering, 2014, Bel�m, PA, Brazil. https://www.researchgate.net/publication/295813779_DESIGN_OF_A_FOREIGN_OBJECT_DAMAGE_FOD_SC