The effect of ship size on airwake aerodynamics and maritime helicopter operations

Abstract

This paper describes an investigation that has used piloted flight simulation to assess pilot workload while manoeuvring a helicopter over the landing decks of three different size, but similar, ships. Three generic ships with lengths of 100m, 150m and 200m were created to be representative of the range of size of single-spot ships that operate with maritime helicopters. Ship airwakes were produced using unsteady CFD simulations for a range of free stream wind speeds from 20 knots to 50 knots for a headwind and Green 45° Wind Over Deck. To reduce the numbers of expensive and computationally intensive airwakes that have to be produced for simulated deck landings it has been demonstrated that for a given wind angle it is possible to Strouhal-scale the airwake velocities from one representative wind strength to other wind strengths, and from one ship size to another ship size with accuracies which are considered acceptable for their implementation within a flight simulator. Simulated deck landing trials for each of the three ships were used to provide subjective pilot workload ratings. It was found that the pilot workload generally increases with the ship size and that, despite the landing area being larger and the superstructure proximity being less threatening, the more aggressive airwake from the larger ship still makes the aircraft more difficult to control over the larger ship.