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Ames Research Center has designed, developed, integrated, and put into operation a state-of-the-art full-motion simulator for the Joint Shipboard Helicopter Integration Process (JSHIP) program. JSHIP is a Joint Military Test and Evaluation program, sponsored by the Office of the Secretary of Defense (OSD) to develop and test the processes and mechanisms that facilitate joint helicopter and ship operations. JSHIP has teamed with Ames Research Center to develop a man-in-the-loop simulator that replicates the dynamic interface of an LHA-class ship and a UH-60A Blackhawk helicopter. The objective was to develop a simulator capable of being used to define wind-over-deck (WOD) launch and recovery flight scenarios providing increased interoperability of helicopter units not specifically designed to go aboard Navy ships.
The project required identifying, analyzing, and developing a simulation system to support the definition of helicopter/shipboard launch and recovery envelopes. Key simulation components included a compact, low-cost, wide-field-of-view, night-vision-capable, cross-cockpit visual system; a low-cost, high-resolution, PC-based image generator; integration of a four-axis dynamic seat shaker; a motion-rated simulator cab capable of operating on NASA's Vertical Motion Simulator (VMS) motion system; a visual database capable of simulating accurate ship and deck motions; a three-dimensional textured ocean and other visual effects; and a ship dynamics model, with airwake, representing various wind and ocean states. Figure 1 shows the simulator cab interior with the visual presentation of the ship and sea.
The new visual display system was designed to provide a 220-degree horizontal x 70-degree vertical, night-vision-goggle-compatible, continuous out-the-window field of view. This system provided all the benefits of a spherical screen at one-fifth the cost. The system consists of five off-the-shelf, high output cathode ray tube (CRT) projectors combined with custom mirrors and rear projection screens. The complete visual projection package is extremely compact and fully motion-rated to 3 g's.
The major challenge and enhancement to the simulation was the development of a wind-over-deck airwake model for a ship with a large superstructure on one side of the landing deck. This airwake, which is highly complex and varies drastically depending on the direction of the incoming wind, is one of the most critical elements a pilot must deal with while landing a helicopter on a ship. To address this critical issue, an unsteady airwake model, developed using computational fluid dynamics (CFD) technology, was integrated into the simulation. This innovation has allowed, for the first time, an accurate representation of the wake problem. The mathematical model integrates airwake forces at 24 different points on the helicopter, including the segments of each rotor blade, the fuselage, horizontal and vertical tail, and the tail rotor. Additionally, ship-motion, landing gear, cross-coupling and engine transient dynamics were incorporated in the model.
The new simulation system provides an outstanding platform for developing WOD launch and recovery flight envelopes that will increase interoperability of helicopter units not specifically designed to go aboard Navy ships. Additionally, the system has tremendous commercial market application in developing helicopter procedures for offshore oil platforms and inner city skyscrapers where turbulence is a major problem.
Point of Contact: D. Giovannetti
(650) 604-3871
dgiovannet@mail.arc.nasa.gov
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Fig. 1. Simulator cab with external visual scene.
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