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Title: Modelling and Simulation at The University of Liverpool in Support of UK Naval Aviation

Author(s): Ieuan Owen, Mark White, Paul Scott, Rebecca Mateer, Mike Kelly

Abstract: The operation of maritime helicopters to naval vessels at sea can be a difficult and dangerous task, particularly for single-spot combat ships. Along with the restricted landing area and the rolling, pitching and heaving of the ship's deck, the pilot also needs to contend with the turbulent wake produced by the air flow over the ship's superstructure. There has been significant research in the past decade or more to understand better the flying environment around the ship and how it impacts the helicopter flying qualities and pilot workload. Central to this research has been the development of a high-fidelity modelling and simulation environment, with a particular emphasis on motion-base flight simulation which can appropriately reproduce the conditions experienced by a pilot as the aircraft is recovered to the ship. To create the simulation environment and present the pilot with appropriate visual and aural cues it is necessary to provide full motion and aircraft flight mechanics models which operate in a real-time maritime environment; importantly an unsteady CFD-generated airwake is also required to disturb the aircraft when it is within the ship’s airwake. In the UK, this flight simulation research has been led by the Flight Science and Technology Research Group at the University of Liverpool. This paper will review the research that has been carried out at Liverpool, and how this has led to simulated flight trials to establish a simulated Ship-Helicopter Operating Limits envelop (SHOL). Research into improving the simulation environment continues to be a priority at Liverpool; however a second strand of research has also been vigorously pursued and which is of direct interest to ship designers, i.e. the use of flight modelling and simulation to assess the aerodynamic characteristics of the ship while it is still in the design phase. This research uses both a motion-base piloted assessment of the ship aerodynamics, and an offline software-based technique that asses the unsteady loads imparted by the airwake onto a helicopter but without a pilot in the loop. The research has been used to generate simulated SHOLs for a frigate and a fleet auxiliary vessel in the Liverpool simulator, and to enable simulation trials in the Royal Navy Merlin training simulator as part of the UK MoD’s Ship/Air Interface Framework (SAIF) programme. Current work involves the development of a simulation environment for the UK’s new Queen Elizabeth Aircraft Carriers for both STOVL and rotorcraft launch and recovery operations. (we are submitting a separate paper to L&R 2016 on this research). The offline and piloted simulation techniques have been used to assess the effect of superstructure modifications on a simplified ship geometry, and have also been applied to a future combat ship in the design phase; aspects of this work will be reported as will new research to establish simulation fidelity requirements so that simulation can used with a level of confidence to inform the process of producing operational clearances.