SIMSHOL: A Predictive Simulation Approach to Inform Helicopter-Ship Clearance Trials

This paper presents the development of a simulation framework, SIMSHOL, which has a predictive capability to inform and support real-world ship-helicopter operating limit trials for a range of helicopter-ship combinations. SIMSHOL is a desktop-based predictive simulation tool that presents an objectively optimized human pilot modeling technique within an integrated pilot-vehicle-environment that represents the helicopter-ship dynamic interface (HSDI). The overall scheme employs a multiloop pursuit "paper" pilot model, a linearized helicopter flight dynamics model with a new enhanced spatial turbulence model, together with an objective optimization loop. To simulate the ship-airwake turbulence effect, a new spatial airwake disturbance modeling technique has been developed, which, in real time, captures the spectral characteristics of the turbulence around the ship from acomputational fluid dynamics-computed ship airwake. Time- and frequency-domain comparisons have been made between SIMSHOL and piloted simulation flight trial experiments. It was observed that the performance of the SIMSHOL tool in maintaining sufficient clearance between the aircraft and the ship's landing deck and hangar, while rejecting airwake disturbances, is well within the desired task performance boundaries. These investigations have shown that the tool is capable of representing the dynamics of a pilot-vehicle-task system in the challenging HSDI environment. Moreover, an automatic error-minimization-based response optimization methodology has been developed and used, which uses the iterative gradient descent optimization algorithm to objectively tune the pilot-vehicle loop transfer functions to represent a pilot's performance in the simulator. The results show that SIMSHOL is able to predict operational limits for a range of different helicopter-ship and environmental combinations.