The Rena disaster could have been avoided if the ship's captain had correctly interpreted radar echoes bouncing off Astrolabe Reef nine minutes before impact.
A report into the grounding released today indicated that the captain was under pressure to reach Tauranga before the ebbing tide made it unsafe to bring the ship into port.
The Transport Accident Investigation Commission's report avoided casting blame and instead set out the facts about what happened in the days and hours leading up to the grounding at 2.14am on October 5, 2011.
It detailed how Tauranga Harbour Control asked Rena to make "best speed" for its rendezvous with the port's pilot boat off Mauao after Rena radioed that its estimated arrival time would be 3am. Harbour control advised that 0300 (3am) was the end of the window for possible pilotage into the port.
The report painted a picture of a disaster preceded by pressure on the captain to reach the port on time, starting with delays at Rena's last port of call, Napier, and a succession of course changes.
Rena was being steered by autopilot for most of the voyage, including the final couple of hours. The report detailed the difference between the Rena's gyro (true north heading) which guided the autopilot and the ship's ground track course, which is a vessel's track in relation to the seabed.
By 12.30am on October 5, five hours after rounding East Cape, Rena was making two degrees to the south of the vessel's true north heading, because of the influence of wind, current, tides and gyrocompass error, the report said.
A key point in events leading up to the radar echo was when the watchkeeper went to plot the ship's position at 2am onto a chart.
The seaman read the position off the global positioning system in the chartroom and recorded it in the position log book.
"The master and second mate were leaning over the chart as they talked, so rather than interrupt them the able-bodied seaman did not plot the 0200 position on the chart," the report said.
The captain then went to the wheelhouse to familiarise himself with the situation and monitor the radar.
The second mate told the commission that he showed the master the charts and pointed out the changed course, including a navigation mark about one nautical mile north of Astrolabe Reef.
The captain said he did not study the charts. At 2.05am, nine minutes before impact, the captain noticed an intermittent echo on the radar about 2.6 nautical miles dead ahead.
The master showed the echo to the watchkeeper and peered through binoculars out through the windows of the bridge to find the cause of the echo.
"They could not see anything, so they moved to the bridge wing to look from there. When again nothing could be seen, the master said that he decided to plot the Rena's position on the chart, so began to walk through the wheelhouse to the chartroom."
As the captain was making his way to the chartroom, the Rena struck Astrolabe Reef at a speed of 17 knots (31km/h).
The report set out how the ship was delayed at Napier by 13 hours after a priority booking displaced it. It sailed for Tauranga on October 4 at 9.20am.
The captain told the shipping agent they would arrive at Tauranga at 2.30am the next day, based on keeping to the passage plan. He then modified the passage plan around Mahia Peninsula to shorten the distance. When the Rena was near the tip of the peninsula, he told the second mate to take the inshore side of the course lines plotted on the chart. The second mate did this, reaching up to five nautical miles inside the planned passage.
The report said this was in order to assess the strength and location of any unfavourable current. The captain also told the second mate to search for the least unfavourable current on either side of the chart course lines while navigating up the East Coast.
At 1.35am on October 5, the second mate called the captain on the telephone. During the discussion the second mate confirmed that the vessel would be at the pilot boat station by 3am. He also discussed a course alteration which would shorten the distance to the pilot station, to which the captain agreed.
At one point, the second mate said he marked a point with a pin-prick using a drawing instrument and not a pencil, so it was not immediately obvious to anyone other than him, the report said.
"The second mate had already begun to progressively make the alteration to the course."
The report said his plan was to navigate closer to Astrolabe Reef. The second mate said he placed a mark on the chart about one nautical mile north of the reef, before making a series of small course adjustments which took the Rena closer to Astrolabe Reef.
The master subsequently stated that the mark was put there after the grounding.
At 1.42am the Rena's actual groundtrack was still towards Astrolabe Reef, two degrees south of the true north gyro heading. Eight minutes later, Rena was still making two degrees and heading directly for the reef.
The captain arrived on the bridge at 1.52am. He discussed the radar picture with the second mate. Shortly after, the next waypoint which the GPS was monitoring was moved from just north of Astrolabe to the one at the pilot boat station. Six minutes later the master removed the parallel index lines from the radar because he thought they were cluttering the radar screen.
- Course changes to shorten the distance to the pilot boat takes Rena toward Astrolabe Reef.
- Watchkeeper does not plot Rena's 2am GPS position on the chart because the captain and second mate were leaning over the chart talking.
- Two degree variation to the autopilot's true north course.
- Captain and watchkeeper fail to realise the significance of an intermittent echo dead ahead on the ship's radar.
- Rena told to make best speed to meet the Port of Tauranga's pilot boat.
- There is conflicting evidence as to whether a new mark on the chart one nautical mile north of the reef was drawn in before or after the incident.
- Captain removes parallel index lines from radar picture because they were "cluttering the screen".
- A 1am GPS position plotted on one chart was not transferred to a second chart on which the 1.20am position was plotted.
- A position had been placed on the chart using a pin-prick from a drawing instrument, rather than a pencil.
The parameters of the report
The Transport Accident Investigation Commission has released an interim report of its independent inquiry into the grounding of the container ship Rena on Astrolabe Reef, in the Bay of Plenty, at 2.14am on October 5, 2011.
The report sets out facts of the accident that have been able to be verified to date but does not contain analysis of why events happened as they did or say what could change to help prevent a recurrence. These matters will be covered in the commission's final inquiry report.
This interim report includes information from the crew interviews, information retrieved from the voyage data recorder, information from the log books and other documents either removed from the Rena or supplied by the Rena's owners, and information retrieved from the automatic information system. Raw automatic identification system data is transmitted from the vessel and recorded by several shore stations. The raw automatic identification system data used in this report was provided by a maritime consultant, Marico Marine NZ Limited, and was verified with data from the voyage data recorder.
In the interests of natural justice, a draft interim report was circulated to interested persons in December last year. The interested persons were the master of the Rena, the second mate of the Rena, the third mate of the Rena, the watchkeeper on watch at the time of the grounding, the vessel's owners, the vessel's charterers, Maritime New Zealand, Bay of Plenty Regional Council, Port of Tauranga and Crown Law. The draft report was assessed and amended with respect to the submissions received from the interested persons.
The submissions raised a number of matters more relevant to the final analysis that are not addressed in this interim report but will be addressed in the commission's full report.
The interim report concludes by saying that the commission is continuing to collate and verify information directly related to the grounding and is also pursuing several lines of inquiry of a wider systemic nature.
The commission's inquiry is completely independent of Maritime New Zealand's regulatory action, environmental enforcement action, or financial claims relating to the grounding.
In order to encourage co-operation from accident participants, the commission's reports, which are intended to help improve transport safety rather than to lay blame, may not be used in criminal or civil proceedings.