Known Propulsion Problem Caused Berthing Accident
The UK Marine Accident Investigation Branch has released its report into a berthing accident that occurred on 20 December 2013. The 93m chemical tanker Key Bora made heavy contact with the western approach jetty at Alexandra Dock, Hull. The vessel’s controllable pitch propeller (CPP) system had a history of responding slowly to demands for astern pitch, and did not respond in time to the pilot’s order of full astern to prevent the bow striking the quay. The bulbous bow was holed above the waterline, there was no pollution.
The MAIB investigation identified that:
The pilot was aware of the vessel’s poor astern response but did not test the engine prior to maneuvering.
The master was unaware of the function of the CPP backup control system which could have been used to bring the situation under control.
The crew at the anchor station had difficulty hearing the master’s order to drop the anchor over the hand-held UHF radio.
Fault finding and assessment of the CPP system performance was hampered by the lack of installation records against which to judge the system’s response.
The port authority, ABP, has taken steps to ensure that astern propulsion is tested and ready for use before departure or arrival from any berth, regardless of the vessel’s size. The vessel’s manager, V.Ships, has been recommended to investigate and rectify the anomaly with the CPP system on Key Bora and to include in its safety management system a requirement for bridge watchkeeping officers to familiarize themselves with the emergency backup control of their CPP system.
Following a recommendation from the chief inspector, BV has requested IACS to include response times in its forthcoming unified requirement for commissioning trials on CPP systems.
• Key Bora made heavy contact with the jetty because the CPP’s astern response was inadequate and did not develop sufficient astern thrust in time to stop the vessel.
• The CPP control system astern response was four times slower than the ahead response to 50 percent demand.
• It is almost certain that the poor CPP astern response was introduced at the time the system was commissioned in 2005.
• Fault finding and assessment of the CPP system’s performance by the crew, the operator, independent technicians and surveyors was ineffective due to the lack of a performance standard against which to judge the system’s response.
• Having not tested the propulsion system, the pilot was unable to fully assess the risks presented by the poor astern response and so did not put in place sufficient control measures.
• The master’s lack of familiarity with the backup control system meant that he was unable to intervene effectively to prevent the vessel striking the quay once it was clear that Key Bora was not slowing quickly enough.
• Had the talkback system been functioning and used, the command to drop the anchor would probably have been heard clearly and implemented much sooner.
The report is available here.