NTSB: Autopilot confusion likely caused ITB to run into docked cutterJun 1, 2015 12:38 PM
The integrated tug-barge (ITB) Krystal Sea/Cordova Provider was approaching port in Cordova, Alaska, in heavy fog when the captain realized there was a problem: The vessel was going too fast.
Although he had more than 40 years of maritime experience, the captain had only a week aboard Krystal Sea. He reduced the throttle and rotated the azimuthing stern drives (ASDs) 90 degrees outboard to slow down.
Still, the vessel overshot its destination at the Alaska Marine Lines pier and headed toward the 225-foot Coast Guard cutter Sycamore moored nearby. The captain again tried to reduce speed and swing the bow away from the cutter, which may have worked had he noticed that the starboard ASD was still on autopilot and working against him.
“The captain sounded five blasts on the ship’s whistle as a danger signal. After two blasts, the ITB’s bow ramp struck the port bow of the moored Sycamore at about a 45-degree angle and slid down the cutter’s bulwark,” according to a National Transportation Safety Board (NTSB) report on the incident.
The incident on July 28, 2013, caused extensive damage to the cutter’s hull, although nobody on either vessel was hurt. Federal investigators determined that the likely cause of the accident was the captain’s failure to recognize that the autopilot was still engaged.
“The probable cause … was the loss of directional control of one of two azimuthing stern drive propulsion units during an unsuccessful attempt by the Krystal Sea’s new captain to transfer from autopilot to manual control while approaching the intended dock,” the NTSB wrote.
Krystal Sea left Whittier, Alaska, during the evening of July 27, 2013, for the 12-hour voyage to Cordova. The 260-foot ITB is capable of hauling 36 40-foot containers, although on this run most boxes were empty.
Krystal Sea was the first vessel the captain had operated with ASDs, the report said. He trained on the tug for about a week before the accident, during which time he witnessed and performed docking maneuvers under supervision of a senior captain.
“The senior captain said he was very comfortable with the performance of the new captain,” the report said.
The trip to Cordova was uneventful during the overnight hours. The captain relieved the mate at 0600 and the vessel approached the Alaska Marine Lines pier about an hour after sunrise. Low clouds and heavy fog reduced visibility around the port, the report stated.
About one-third of a mile from the pier, the captain pulled back on the throttle and reduced speed to about 7.5 knots. About this time, he disengaged the autopilot and shifted the port and starboard ASDs into manual in preparation to land the vessel. He rotated the drives to help slow down. The vessel was still going too fast.
“He first thought the following current was pushing the ITB forward, and in response he gave both ASDs more thrust because greater outboard thrust slows the vessel at a faster rate,” the report said. “He stated that at the corner of the AML dock, with the bow of the barge about 350 feet from the Coast Guard cutter’s bow, the ITB was at a 45-degree angle to the pier and still not slowing as expected.”
The port ASD was responding to manual helm inputs, but the starboard drive was still in autopilot and trying to maintain the last course input toward the Alaska Marine Lines pier, investigators found.
Krystal Sea requires a three-step process to disengage the autopilot, and the captain was accustomed to operating vessels that require just one button. He thought he pressed all three buttons in the proper sequence on the morning of the accident, the report said. However, the mate who entered the wheelhouse just after impact noticed right away that the autopilot light was still on.
The impact, which occurred at about 0616, bent inward a 41-foot-long section of Sycamore’s bulwark and damaged pipe vents, a 50-caliber gun mount and other components. There was no damage below the waterline. Repairs cost almost $244,000.
Damage to Krystal Sea/Cordova Provider, including the barge’s ramp, was minimal. Repairs cost about $5,000. The vessel is owned by Bering Marine Corp., a subsidiary of Lynden Inc., a large logistics and shipping company with offices in Anchorage and Seattle.
“The Coast Guard concurs with the reports and findings of the National Transportation Safety Board regarding the collision,” said Kip Wadlow, a spokesman for Coast Guard District 17 in Alaska. “Upon receipt of the claim for reimbursement for the damages, Bering Marine Corp. paid the damages promptly and the claims were resolved without controversy.”
David Rosenzweig, Lynden’s vice president of marketing and media, described the accident as “unfortunate” and said the company was glad nobody got hurt.
At the time of the accident, Bering Marine’s safety management system required captains to disengage autopilot “at an adequate distance” from dock and to test manual controls before approaching the dock.
The company implemented new safety rules after the accident requiring operators to disengage autopilot at least a half-mile from the docks and make sure steering and throttles are responding as expected. The company placed similar instructions in Krystal Sea’s wheelhouse directly under the autopilot controls.
The instructions indicate the autopilot light on means the autopilot function is still engaged.