BNWAS Alarm Didn't Prevent Accident
The U.S. National Transportation Safety Board (NTSB) has released a Marine Accident Brief about an accident that occurred in March 2019, involving the towing vessel Dixie Vandal, noting that the BNWAS alarm didn't prevent the fatigued pilot from falling asleep.
At 0408 local time on March 15, 2019, the Dixie Vandal, pushing a partially loaded fuel barge upbound through the Houston Ship Channel, struck the towing vessel Trinity and one of its barges, which were moored and preparing to discharge cargo at the Kinder Morgan Pasadena Liquids Terminal in Pasadena, Texas.
The contact caused the Trinity and its tow to shift about 100 feet upriver, breaking the cargo hoses and mooring lines and damaging the facility. About a half-gallon of jet fuel discharged into the channel. No injuries were reported by the crew of five aboard the Dixie Vandal nor by the Trinity’s crew of four. Damage to the facility and barges amounted to $630,230.
The NTSB determined that the probable cause of the collision was the fatigued pilot falling asleep near the end of his 12-hour watch while maneuvering in the Houston Ship Channel. Contributing to the pilot’s fatigue was the extended length of duty through the night and early morning hours and his use of an over-the-counter antihistamine.
During the pilot’s typical 12-hour watch, his duties varied, depending on the operations that were being conducted. If the vessel was transiting or docked in a restricted area, the pilot was required to be in the wheelhouse. If the crew was engaged in bunkering vessels or cargo-loading of the barge, he was not restricted to the wheelhouse and would monitor the fuel transfer from several locations on the vessel.
The pilot stated that he could not recall a time when he was restricted to the wheelhouse for an entire 12-hour shift. He said eight hours was the maximum time he had been required to maneuver in the wheelhouse at one time, given that their transits were generally eight hours or less. The tankerman on watch with the pilot was typically assigned duties outside the wheelhouse such as cleaning the vessel; the pilot believed that he was in the galley at the time of the accident.
Based on the records the pilot provided for his work-rest history for the 96 hours prior to the accident, he worked each day from 1800 until 0600, was off duty from 0600 until 1800, and slept from 0800 until 1600. At the time of the accident, the pilot was on his tenth day of a 20-day rotation. The pilot stated that during the time he was off duty from the vessel, he remained awake during daytime hours; when he returned to the vessel, he reported that he had no issues adjusting from being awake during the day while at home to having to be alert at night while working on the vessel.
The pilot did not recall hearing the BNWAS alarm on the bridge. There was no evidence to suggest the system was deactivated or inoperable at the time of the incident, so the NTSB postulates that the sensors detected motion in the wheelhouse just before the pilot fell asleep or while he was drifting off to sleep within the time frame of the setpoints of the BNWAS system. As a result, it did not sound in the wheelhouse nor did the general alarm sound throughout the vessel before the collision.
According to the pilot, the crew—consisting of the captain, the pilot, and three tankermen—had been operating on a 12-hours-on/12-hours-off schedule for about 1.5–2 years. According to a company representative, after the accident, the crew switched to a six-hours-on/six-hours-off watch schedule.
The report is available here.