MAUNALEI

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Report: Substandard propellor blade caused propulsion loss

A substandard propellor blade caused a loss of propulsion and large spill of hydraulic oil from the 'Maunalei' in August 2022. The ship lost power as a result of a flawed propeller blade on a voyage between Anchorage and Portland according to a US National Transportation Safety Board (NTSB) investigation. The NTSB revealed its findings on May 21, 2023, concluding that the vessel’s controllable pitch propeller had failed to meet design requirements. En route to a drydocking in Portland, theship’s controllable pitch propeller failed, resulting in a loss of propulsion about 245 nautical miles from the entrance to the Columbia River, close to Portland. The vessel’s propeller system was thought to have lost more than 1,632 gallons of hydraulic oil and resulting damage has been estimated at $3m. The NTSB concluded that the manufacture of the propeller was substandard. Cracks and fractures at the base of the fourth blade in the five-blade propeller failed to meet specification requirements and did not meet requirements for impact toughness, tensile, or yield strength. The NTSB investigators concluded that the blade damage was probably an isolated incident. The analysis of other five-bladed propellers on similar vessels indicated no problems. However the blade manufacturer has adjusted the specification to improve propeller fatigue fracture resistance. Full report: https://www.ntsb.gov/investigations/AccidentReports/Reports/MIR2411.pdf