Advanced modeling and flight control design for gust alleviation on ship-based helicopters

Some of the most challenging and highest workload tasks for pilots performing maritime missions are shipboard launch and recovery operations. Pilots continuously need to compensate for gust disturbances due to both atmospheric turbulence and the turbulent air wake of the ship. Therefore this research concentrated on the development of an airwake compensator for the control laws which has the ability of reducing the pilot workload in the lateral, longitudinal and yaw axes. These airwake compensators were embedded into an already optimized and pilot-evaluated S-92-class fly-by-wire (FBW) rate command attitude hold (RCAH) control system. Using an extensively developed simulation model of a DDG-81 shipboard environment, which included a full CFD airwake model, and a Maritime mission task element (MTE) based on the visual cues found on the ship deck, a pilot evaluation of the airwake compensator control laws was performed. The piloted evaluation showed that by having a ship airwake degraded the Cooper-Harper handling quality ratings (HQRs) on average by 1.5. Implementing the airwake compensator showed an improvement of 0.4 HQRs for the 25 kts airwake. Similar improvements were also seen for the 40 kts airwake case as well. Power spectral densities (PSD) of the pilot's cyclic stick and pedal inputs showed moderate improvement when the airwake compensator was activated.