Containership Loses Propulsion Due to Cracked Propeller Blade

A crack in a propeller blade of a Matson containership led to a loss of hyrdraulic oil and propulsion while transiting the Pacific Ocean, the National Transportation Safety Board (NTSB) said Tuesday.

The incident, which occurred on August 11, 2022, resulted in a loss of up to 1,632 gallons of hydraulic oil and an estimated $3 million in damage.

The probable cause has been traced back to a cracked blade on the vessel’s controllable pitch propeller (CPP) system, which investigators discovered did not meet manufacturer design specifications.

The U.S.-flagged Maunalei, a 681-foot-long containership, is owned and operated by Matson Navigation Company, Inc., a subsidiary of Matson, Inc. The vessel was en route from Anchorage, Alaska, to Portland, Oregon, for drydock repairs when the crew intentionally shut down the main engine due to problems with the propeller system. This resulted in a loss of propulsion approximately 245 miles from the entrance to the Columbia River near Portland.

Upon drydocking, a third-party company found cracks and fractures at the base of the no. 4 blade of the 5-bladed propeller, where the blade was bolted to the propeller’s hub. The cracks, which began at the blade’s bolt hole counterbore radius, were consistent with progressive cracking due to high-cycle fatigue. The company also found that the no. 4 blade did not meet manufacturer design specifications for engineering, material, and chemical composition. The bolt hole counterbore radius was 0.2 millimeters smaller than the required 0.8 millimeters, and the materials did not meet specifications for impact toughness, tensile and yield strength, or percent elongation. Additionally, the silicon content exceeded the specified minimum.

The NTSB investigators concluded that the crack and fracture on the no. 4 blade were likely isolated occurrences, as the blade did not meet specifications, and a manufacturer’s analysis of other five-bladed controllable pitch propeller systems on similar vessels did not identify any other instances of cracks.

In response to the incident, the blade manufacturer has revised the internal radius requirement, enlarging it for all seven-bolt hole counterbores, in a bid to improve fatigue fracture resistance.

Read the NTSB report here.

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