Aratere grounding began with a 36-second autopilot mistake

The grounding of the ferry Aratere began with a "turn execute" command being pushed 36 seconds late, sending the ship's autopilot onto a course crew didn't know how to stop, a preliminary report has found.

Transport Accident Investigation Commission chief commissioner David Clarke and chief investigator of accidents Naveen Kozhuppakalam have spoken to media about the agency's interim report on the 21 June grounding of the Cook Strait ferry, which has been released on Thursday.

The Aratere ship ran aground shortly after departing Picton at 9.45pm on 21 June - prompting inquiries from the transport agency, Maritime New Zealand and TAIC.

None of the 47 passengers and crew aboard were injured and the ship was refloated just under 24 hours later.

TAIC's report drew evidence from the ship's voyage data recorder, the steering control system and interviews with crew.

It confirmed details RNZ reported from leaked documents in July, that a crew member had triggered the autopilot into the wrong course before it crashed into the shore.

The report showed the crew did not know how to take back control from the autopilot, and it took about two minutes before the ship was brought back under manual control.

The TAIC report showed that a new Kongsberg steering system had been installed on the Aratere just weeks prior in May, and 83 inter-island crossings were made in the three subsequent weeks.

In response to questions about why crew did not know how to switch off the autopilot function, Clarke told media this was one of the lines of inquiry as investigations into the groundings continued.

Staff know about button now - KiwiRail boss

Speaking on Checkpoint, KiwiRail executive general manager Duncan Roy said the single-push control button had worked on every sailing until 21 June.

If they had known how to override the autopilot - and, indeed, had known that this was a new procedure - they would have trained bridge staff on how to do that, he said.

Checkpoint host Lisa Owen asked whether Kongsberg should have told KiwiRail about the critical change.

"We need to work on our management of change. We need to know what we need to know, so we can train it."

Pressed on who was at fault, Roy was reluctant, saying only that it was "complex" and investigations were still ongoing.

Immediately after the grounding, all crew were retrained and manuals updated, he said.

Crew now knew "categorically, for sure" how to manage the system, and were subject to "controlled verifications" to ensure they did, he said.

On 21 June alongside the day and night master, an additional experienced master was also onboard refamiliarising themselves with the ship, and was pilot instead of the night master.

Also present was an officer of the watch, a lookout and a helmsman.

A reporter asked TAIC whether the so-called "refamiliarisation officer" was being adequately supervised by the night master.

The co-pilot or night master was the final decision-maker, Clarke said, but at the time he was carrying out the additional function of familiarising another master with the vessel's controls, which was a separate process to the unfolding event.

Kozhuppakalam said the Aratere was just past its second waypoint off Mabel Island when the autopilot was engaged at 2126:01, putting steering for the Aratere under autopilot control.

"At 2126:30, the re-familiarisation master pressed the turn execute button, intending to initiate the Mabel Island waypoint turn.

"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."

He said around 31 seconds after the 'execute' command, the night master saw Aratere was 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."

He said the bridge team were unaware that to transfer steering control from the autopilot to the central steering console, the new steering system required them to either set the same rudder command at both consoles, or hold down takeover button for five seconds.

They were also asked if everyone on the bridge could see the indicators showing the direction of the starboard and propeller rudders.

They were easily viewed by the master who had control of the vessel, but their visibility for other crew members would be part of TAIC's wider investigation.

At 2127:43, with Aratere heading towards shore at 13 knots and helmsman lacking steering control, 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.

At 2128:06 the manual steering mode was engaged.

By 2128:34, Aratere had slowed to about 7 knots at the 10-metre sounding, then slower, and by 2128:50 it had grounded.

TAIC was asked if the outcome might have been worse if the crew had not reversed the engines as soon as the error was discovered.

Clarke said if those steps were not taken, and the vessel was travelling at a significantly higher rate, there was the potential for greater damage but further "speculation" was "not helpful", he said.

No mention of crew member going for coffee

They were also asked if there was any substance to earlier reports that a crew member had left the bridge to get a coffee.

Kozhuppakalam said TAIC's interim report merely showed the sequence of events and facts from evidence collected to date.

"The narrative is in the body of the report; that is the commissioners' view at this stage."

Following the grounding, the Aratere's hull remained watertight, but the ship did sustain damage to the internal structure of the bulbous bow that had to be repaired.

The Commission will issue a final report on completion of its investigation.

Read more:

• Timeline: A recent history of Cook Strait ferry woes
• How Labour's compromise over iRex ferry project led to $100m 'cost burn'
• Should a new entity be set up to run Interislander ferries?

KiwiRail response

In a statement, Interislander executive general manager Duncan Roy said the company was implementing improvements in the wake of the Aratere grounding.

"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," Roy said.

After the grounding, Interislander worked with Kongsberg - which provided the new steering system - to understand what had 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."