A captain's decision to leave the wheelhouse unattended while transiting the St Marys River on autopilot led to the grounding and sinking of a fishing vessel south of Cumberland Island, Georgia, on June 9, 2021, the National Transportation Safety Board (NTSB) said in a Marine Investigation Report released recently.
On the said date, the fishing vessel Sage Catherine Lane was transiting outbound on the St Marys River when it grounded on the north jetty of the St Marys Entrance channel.
After Sage Catherine Lane began to flood, the three-person crew abandoned the vessel and were rescued by a nearby Good Samaritan vessel.
The fishing vessel later sank with about 2,300 gallons (8,700 litres) of fuel, engine oil, and hydraulic oil on board. A crewmember sustained a minor injury.
The vessel was declared a total loss at US$1 million.
As the vessel was transiting outbound, the captain set the vessel's autopilot to maintain the vessel's heading out of the inlet. He answered a phone call and left the wheelhouse.
Shortly afterwards, the captain felt the vessel turn abruptly to port. He returned to the wheelhouse and attempted to turn away from the jetty, but the vessel struck the jetty and grounded.
The vessel broke apart and sank following a thunderstorm three days after the grounding.
Two days before the grounding, the captain was unable to disengage the autopilot and gain control of the helm as the vessel was proceeding into St Augustine.
The captain examined the autopilot system and found problems with the rudder angle indicator and rudder angle sensor at the rudder post. He took actions to correct the problems, which appeared to have worked initially; however, the vessel's sharp turn to port indicated the system failed and the repairs were not effective.
"Leaving the wheelhouse unattended is imprudent, especially when navigating areas like the St Marys Entrance, which included a narrow navigation channel, two jetties and vessel traffic," the report said. "Had the captain stayed in the wheelhouse after engaging the autopilot, he would have been able to respond and take control of the vessel after the autopilot system failed and caused the rudder to turn to port."
The NTSB determined the probable cause of the grounding of Sage Catherine Lane was the captain's decision to leave the wheelhouse unattended as the vessel transited the St Marys Entrance on autopilot, leaving insufficient time to respond when the autopilot failed and caused the vessel to go off the set course.
"Autopilot use does not relieve the operator of responsibility to conduct a proper navigation watch," the report said. "Use of autopilot should not be a justification for an operator to leave the wheelhouse or bridge unattended in confined waters.
"Navigating in channels and harbours requires quicker reaction times due to traffic, currents encountered, and frequent course changes, and more rudder due to slower speeds. Therefore, autopilot use is often discouraged or prohibited in a harbour entrance or narrow channel."
