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Title: LHA 8 Ship Airwake and Anemometer Position Evaluation Analysis

Author(s): Susan Polsky and Joshua Butler

Abstract: Ship topside structure can generate airflow environments that increase pilot workload and degrade aircraft performance relative to land based operations. In the past, the impact of ship generated turbulence (ship airwake) on aircraft operations was generally not investigated until flight testing (after both the ship and aircraft were built). Over the past decade NAVAIR and ONR have invested in technologies to enable assessment of airwake impact on aircraft launch and recovery during ship design thus providing a decision making tool for acceptance (or rejection) of risk associated with major ship topside changes. This work will summarize application of the NAVAIR airwake analysis tool (the SAFEDI Tool) approach to the LHA(R) Flight 1 with the Reduced Island Concept (RIC) and starboard side sponson forward of the island, which was later renamed LHA 8. The analysis process included application of Computational Fluid Dynamics (CFD) techniques to predict the time varying ship airwake for LHA(R)/LHA 8 and LHD 8. Flight simulation analysis using a generic H-60-like helicopter model was used to determine the impact of LHA 8 airwake on helicopter recovery operations relative to LHD 8. Impact of the new island design on proposed ship mast mounted anemometer locations and ship exhaust stack gas trajectories were also examined. Subsequent to the above analysis and RIC island acceptance, wind tunnel Anemometer Position Evaluation (APE) wind tunnel testing was performed to measure local wind speed and direction distortions at the LHA 8 Class wind anemometer final locations. The results were used to determine the indicated relative wind directions for each anemometer that were acceptable for flight operations. The APE analysis and results for LHA 8 will be summarized as part of this work.