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In the last years during the boom of the global shipbuilding industry, a considerable amount of mechanical azimuthing thrusters (typically pushing arrangements with ducted propellers and pulling arrangements with open propellers) were manufactured and delivered for various applications on different types of vessels, covering wide ranges of operational profiles. Recently, rather large number of gear and bearing failures were reported with those thrusters only after being used in service for half or one year, irrespective of the thruster manufacturers and the ship operators. Obviously the operation of those mechanical azimuthing thrusters have exceeded the design constraints and limits, which were based on the present understanding of hydrodynamic loads on the thrusters and their shafting systems, including gears and bearings. At least two possible reasons have been identified and blamed to have resulted in those mechanical failures. One of them is the extreme maneuvering with the azimuthing thrusters, including interactions, typically for offshore structures both during transit and at dynamic positioning. The other is the thruster ventilation, which occurs both in DP and also in high speed sailing conditions when located close to the free surface. In both cases, large hydrodynamic loads variations and shafting responses occur, leading to the high level transient dynamic loads on the propeller blades, which transmit through the propeller hub and shaft to the underwater gears, the pinion shaft and its bearings.