The Lessons Learnt from Marine Accident Investigations was published in The National Transportation Safety Board (NTSB) SAFER SEAS DIGEST 2017. In this article, we will see about the Allision due to negligence of maintenance procedures.
Access to Vessel Controls and Distraction
Vessel controls that are located outside the bridge/wheelhouse and are accessible to non-crewmembers present the opportunity for tampering and may lead to the distraction of the operator. Owners and operators should designate a perimeter around these stations and ensure the area is secured when in operation.
Remote Propulsion Control Systems
Though not required by regulations, current technology allows vessels to be constructed and fitted with automated instrumentation and alarms that alert the operator in the event of critical failure.
The negative consequences of an undetected loss of propulsion control are elevated for passenger vessels because they carry more people on board, often transit in confined waterways, and dock frequently.
Positive Indication preferred
Owners and operators are encouraged to install instrumentation that provides a positive indication of propulsion thrust direction and/or a deviation alarm at bridge/wheelhouse and remote propulsion control stations.
Such indications/alarms increase the likelihood of early detection of improper propulsion response, thereby allowing the operator time to take effective corrective action.
On the afternoon of March 31, 2016, the passenger vessel Adventure Hornblower was attempting to dock at the Navy Pier in downtown San Diego, California, following a whale-watching excursion.
As the vessel made its approach to the pier, its bow unexpectedly swung to starboard and allided with the pier’s passenger embarkation dock. The Adventure Hornblower then accelerated forward until it struck the seawall at the foot of the pier. Eight passengers sustained minor injuries in the accident. The allision caused nearly $1.06 million in damage to the vessel, pier, and seawall.
The Adventure Hornblower propulsion consisted of twin engines driving their respective propellers through a mechanical transmission. As the vessel approached the pier at about 1245, the captain prepared for docking by first slowing the vessel and then moved vessel control from the wheelhouse to the starboard wing station. She made her normal approach to the dock by “bumping” the throttles forward and then moving them back to neutral, and at some point during the approach, the port transmission did not respond to the command to return to neutral, but stayed in the forward position. When the captain then moved the port throttle to the astern position, the transmission remained in forward.
Captain oblivious of the situation?
The wing station had no indicator to show the position of the transmission, and thus the captain did not know if it was in ahead, neutral, or astern. Similarly, there was no “wrong way” indicator that would have alerted the captain when the port transmission did not respond to the astern command. Because the vessel did not move in reverse when the captain ordered astern propulsion, she increased the throttle, thinking that she did not have enough power for the maneuver. However, with the transmission stuck in the ahead position, this order had the opposite of the intended effect. The Adventure Hornblower surged forward and the bow swung into the pier, striking the embarkation dock at 1255. The vessel then bounced away from the pier and continued moving forward.
As the Adventure Hornblower moved forward, the captain put both throttles in the full-astern position, still unaware that the port engine was engaged in the ahead position. Because the vessel’s propellers operated more efficiently in forward than in reverse, the starboard engine was overpowered by the port engine, and the vessel began to accelerate ahead toward the seawall at the foot of the pier until it hit the seawall.
Neglected longterm maintenance
Investigators learned that, since November 2015, the vessel’s port main engine transmission had been leaking hydraulic oil, requiring replenishment of 1.5–2 gallons of oil each day. A new gasket kit to correct the leak was received in January 2016 but had not yet been installed when the accident occurred. In February 2016, pans were placed under the equipment to collect the leaking oil. Although this was a widely known maintenance issue, it was not regularly noted in the daily engineering checklists, including the checklist left for the captain to review on the morning of the accident.
Investigators also learned that the Adventure Hornblower’s transmissions had not received longterm maintenance every 5 years, or 4,000-6,000 hours, as recommended by the manu- facturer. When the accident occurred, the port and starboard transmissions had more than 66,000 operating hours each, yet the owner provided no evidence that the longterm maintenance had been conducted in the life of the vessel.
Maneuvering commands from the wheelhouse and wing station were transmitted electrically to a control module in the engine room, which then sent command signals to the main engines and transmissions. Transmission signals were routed to an electric-motor-driven actuator, called a servo-actuator. The servo-actuator was linked to the transmission’s control unit selector lever via a mechanical linkage.
Investigators believe that during the Adventure Hornblower’s approach to the pier, a fault occurred between the port transmission’s servo-actuator, its mechanical linkage, and its control unit, most likely due to neglected maintenance of the transmission and control system.
The NTSB determined that the probable cause of the allision of the Adventure Hornblower with the Navy Pier and the downtown San Diego seawall was a failure of the port transmission to disengage from the forward propulsion position due to the operating company’s lack of adherence to the transmission manufacturer’s recommended periodic maintenance schedule and the lack of routine maintenance and upkeep of the propulsion system’s equipment.
Contributing to the accident was the lack of instrumentation to provide positive indication of thrust direction or an alarm to indicate the propulsion control system was not responding properly to the captain’s commands.
Lesson learnt from the accident
This accident illustrates the potential safety hazards of failing to follow the equipment manufacturer’s recommended maintenance procedures and schedules. Without necessary maintenance, equipment cannot be relied on to perform as designed.
Mariners should review manufacturer manuals and guidance on a regular basis to ensure conformance with recommended maintenance plans.
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