The NTSB Investigation: Steering System Failure Leads to Bulk Carrier Collision in St. Marys River

The National Transportation Safety Board (NTSB) has determined that a piece of O-ring-type material debris caused a steering system failure that led to a bulk carrier’s collision with a navigation aid in Michigan’s St. Marys River.

The incident occurred on March 28, 2024, when the bulk carrier American Mariner struck the Munuscong Channel Junction Light near Sault Ste. Marie. The collision resulted in the vessel taking on water, though crews successfully stabilized it using pumps. The accident caused approximately $800,750 in damage to the vessel and $1.25 million in damage to the navigation structure.

Fortunately, none of the 18 crewmembers were injured, and no pollution was reported.

The American Mariner was on its maiden voyage of the season after completing winter maintenance, which included the installation of a new steering control system. During the voyage, the crew noticed intermittent steering system alarms but could not identify their cause, as the rudder appeared to be responding correctly to commands.

Post-incident investigation revealed that the vessel’s No. 1 control motor, responsible for controlling the main hydraulic pump’s stroke, had failed. Technicians discovered black, pliable debris lodged between the control motor’s rotating gears, preventing proper operation. The steering system returned to normal functionality after the installation of a replacement control motor.

Electronic technicians later recalibrated the steering control system, which resolved the alarm issues, suggesting there were also problems with the calibration parameters of the newly installed control system.

The Munuscong Channel Junction Light, which serves as a critical navigational aid in the St. Marys River, consists of a navigational light and signal mounted on a fixed concrete structure.

The NTSB has released the full details of their investigation in Marine Investigation Report 25-18.