AirDyn: An Airwake Dynamometer for measuring the impact of ship geometry on helicopter operations

摘要

This paper describes an experimental study using an Airwake Dynamometer (AirDyn) to evaluate the effect of geometric modifications to a generic frigate shape (SRF), designed to reduce the adverse effects of the airwake on helicopter operations. The AirDyn is a 1:54 scale model helicopter, based on a Merlin EH-101, capable of measuring unsteady forces and moments resulting from the turbulent airwake of a ship. The AirDyn and the SRF have been submerged in a water tunnel, in preference over a wind tunnel. The AirDyn was fixed in space at various locations relative to the flight deck of the SRF and immersed in its unsteady airwake. The forces and moments at the helicopter CoG have been recorded from which Root-Mean-Square (RMS) loadings have been derived and used to analyse the effect of ship modifications in terms of helicopter handling qualities and potential pilot workload characteristics. The implementation of the modifications proved very effective in reducing the severity of unsteady loading caused by the airwake and there is certainly potential that the concepts under development here could lead to tangible reductions in pilot workload at the dynamic interface. A 'Side-Flap' fitted to the windward side face of the hangar and the incorporation of a 'hangar notch' were particularly effective, reducing RMS forces and moments experienced by the AirDyn by an impressive 40-50% at important locations around the flight deck.