Characterization of the wind flow on the flight deck of a frigate

Helicopter operations in frigate-type boats can be critical depending on the sea and wind conditions. Dueto the non-steadiness and wide variations of the mean velocity, the flight envelope is limited, being theapproach to the flight deck one of the most complex and risky operations a helicopter can perform. Usually,the flight deck in the frigates is located in the stern. As a consequence, the wind flow in the surroundingsof the flight deck is highly conditioned by the wake generated by the freeboard of the boat. This wake ishighly turbulent and full of strong vortexes. These vortexes depend on the geometry of the boat upstreamthe flight deck. The correct characterization of this complex flow is related to the safety of the operationof the aircraft and allows to set the limits in which the deck can be operative or be certified. In this work,some partial results of an extensive wind tunnel test campaign are presented. In this campaign, a model ofthe frigate has been tested. The aim is to characterize the flow in the surroundings of the flight deck of thefrigate. For that, visualization tests with wool tufts and smoke, hot wire anemometry and particle imagevelocimetry (PIV) have been performed. All the tests have been done in the experimental aerodynamicsfacilities of the Instituto Universitario “Ignacio Da Riva”, belonging to the Universidad Politecnica deMadrid. Based on the information obtained in the tests, small modifications in the freeboard are suggested,in order to optimize the flow in the flight deck, which can make the approach operation easier for the pilots.