Less than three minutes passed between crew on the Aratere switching on autopilot and the Interislander ferry grounding, an interim safety report has found.
The Transport Accident Investigation Commission has released an initial report into the incident in June, where the Aratere hit the shoreline shortly after departing Picton.
No-one was injured and the vessel was refloated two days afterwards, with damage to its bow that required repair.
TAIC will release a final report with further analysis and any possible recommendations at a later stage – today’s release sets out facts gathered so far.
Aratere was fitted with a new steering control system to work with its autopilot and bridge navigation in May and more than 80 Cook Strait crossings were completed before the grounding.
The vessel departed about 9.20pm on June 21, with a Night Master supervising another Master – who was refamiliarising themselves with Aratere after commanding other ships.
The TAIC report covers the time between 9.26pm and 9.28pm, when the vessel grounded, in detail.
It says the autopilot was engaged at one second past 9.26pm, when Aratere was past its second waypoint off Mabel Island.
At 9.26 and 30 seconds, the re-familiarisation master pressed the ‘turn execute’ button, intending to initiate a turn at the Mabel Island waypoint.
“The Aratere had passed Mabel Island 36 seconds earlier, so pressing ‘execute’ told the ship’s autopilot to make the turn for The Snout headland waypoint, rightward onto a course of 73.8°, which this early in the voyage was towards land,” said TAIC’s Chief Investigator of Accidents, Naveen Kozhuppakalam.
About 31 seconds after this execute command, the Night Master saw the vessel heading towards shore and called the helmsman back to the central steering console.
“In turns, the Helmsman, the officer of the watch and the night master pressed the ‘takeover’ button and turned the wheel hard to port, all to no effect. Aratere continued its turn toward the coast.”
TAIC says the bridge team were unaware that switching off autopilot required them to either set the same rudder control at both consoles, or hold down the takeover button for five seconds.
About 40 seconds later, at 9.27pm and 43 seconds, with Aratere moving at 13 knots and still in autopilot, the night master put both engines at full astern.
“It took 21 seconds for the port propeller and 38 seconds for the starboard propeller to begin turning astern.”
The crew were to switch off the autopilot and resume manual steering at 9.28pm and 6 seconds, turning both rudders to port. The night master also commanded an officer to start a bow thruster.
At 9.28pm and 34 seconds, Aratere had slowed to 7 knots at a depth of about 10 metres. It had grounded by 9.28pm and 50 seconds.
“Aratere’s hull remained watertight, but the ship did sustain damage to the internal structure of the bulbous bow that required repair,” TAIC said.
New guidance on autopilot use
Interislander today said it is implementing improvements in change and contractor management to ensure successful future integration of new systems on its ferries.
“The safety of our customers, the public and our people is paramount. Our response to this incident reflects our commitment to learning from it and doing better,” said executive general manager Duncan Roy.
Immediately following the grounding, Interislander worked with Kongsberg, who provided the new steering system, to look at what happened.
“Having identified the cause of the event, we issued new guidance on the use of the autopilot system and upgraded re-training of deck staff on the control system. This was followed by a full competency test and updated direction on best practice use.
“We are continuing to implement recommended actions based on lessons we have learned in our own investigation. We are focused on training, change management and bridge management, and are continuing to work with Kongsberg. “