Unsteady Aerodynamic Loads on a Helicopter Fuselage In a Ship Airwake

Wind-tunnel experiments were performed to measure the unsteady aerodynamic loading on a rotorless Sea King fuselage immersed in the turbulent airwake of a Canadian Patrol Frigate. A dynamic balance was designed and manufactured to acquire unsteady side force, yawing moment, and drag force. The combination of a lightweight model and a dynamic balance acts as a probe that senses the integrated effect of the turbulent airwake loading on the model. Root-mean-square (rms) loadings, derived from the loading spectra and used to quantify the unsteady aerodynamic loading, were to found to increase with non-zero wind angle and presumed to be proportional to the square of wind speed. A reasonable correlation was found between rms loading levels and pilot workload obtained from flight test. The results highlighted the potential of the airwake probe as a means for evaluating in a wind tunnel the influence of a ship configuration change on the rms loading.