Helicopter Ship Air Interface Modelling

Background: This is an exciting opportunity to join an established research group with an international reputation for its research into flight simulation and maritime aircraft operations. The ability to operate helicopters from Royal Navy (RN) and Royal Fleet Auxiliary (RFA) ships is an essential capability for the UK. However, this is a challenging requirement, due to the difficulties in landing an aircraft to a confined space, undergoing ship motion and subject to complex air flow around the ship’s hull and superstructure. Currently, flight tests are conducted at sea on the actual ship and helicopter combinations for which a ship-helicopter operating limit (SHOL) clearance is required. As well as being expensive and time-consuming, these flight tests do not always produce the ‘widest possible clearance’, due to vagaries of the available weather at the time of the trial. In addition, there are safety issues associated with conducting these trials due to the inherent risks of flying at the extremes of the aircraft’s flight envelope. There is therefore a strong desire to maximise the effectiveness of flight trials through the use of modelling and simulation.

The University of Liverpool is a leading centre for flight simulation research. At the heart of this research is the University’s Heliflight-R flight simulator; a reconfigurable, full motion simulator whose features include a 12ft visual dome with 210x70 degree field of view, a Moog 6 degree-of-freedom electric motion system and force-feedback control loading system. The primary modelling and simulation environment used to develop both rotorcraft and fixed-wing flight models for the simulator is Advanced Rotorcraft Technology’s FLIGHTLAB software. For ship-helicopter operations a flight mechanics model of a maritime helicopter is integrated into an immersive flight simulation environment that allows the pilot to fly the aircraft to and from the ship. As well as a visual model of the ship, and realistic sea-surface and ship motion, an essential component of the simulation environment is the air flow over the ship, which is created using advanced Computational Fluid Dynamics (CFD).

As in all engineering simulations, an assessment of the fidelity of the simulation is an essential part of the process. Significant work has therefore been carried out to understand the air flow over the ship, through wind tunnel tests and use of Computational Fluid Dynamics (CFD), and this aspect of the simulation has been relatively well validated. However the fidelity of the overall flight simulation, which leads to a test pilot assessing the difficulty of the landing task and the associated workload levels, has not been assessed due to a lack of at-sea flight test validation data. Central to this validation process will be the need for fidelity metrics by which to compare the simulated and real-world tasks, and also the criteria required to define what an acceptable, or unacceptable, comparison is. The University of Liverpool has been leading research into the development of fidelity metrics for flight training simulators and through this project aims to make progress towards this goal.

Project Outcomes: The overall aim of the project will be to understand how simulation and flight test can be combined optimally to:

• Inform flight test requirements
• Support interpolation and extrapolation of flight test data
• Support the derivation of operating limitations for a range of helicopters and ships which might not be available for testing.

It is anticipated this will be achieved by undertaking a systematic assessment of the component parts of a SHOL simulation environment to develop an understanding of the individual and collective significance of the elements which contribute to the simulation. Robust metrics will be established which inform the simulation fidelity requirements and utility of any simulation such that it can used with a level of confidence to inform the process of producing operational clearances.