HMNZS Manawanui sinking – human error

HMNZS Manawanui grounded and sunk off the coast of Samoa as a result of human error, the interim Court of Inquiry report shows.

CAPTION: RNZN Divers survey the area around HMNZS Manawanui on the southern coast of Upulo as part of Op Resolution – NZDF’s recovery/salvage operation. NZDF image supplied.

The Royal New Zealand Navy ship grounded on a reef on the southern side of Samoa, on Saturday 5 October 2024 while conducting survey operations.

Chief of Navy Rear Admiral Garin Golding stood up a Court of Inquiry following the incident in order to understand the facts of what occurred.

“The direct cause of the grounding has been determined as a series of human errors which meant the ship’s autopilot was not disengaged when it should have been,” Rear Admiral Golding said.

“The crew did not realise Manawanui remained in autopilot and, as a consequence, mistakenly believed its failure to respond to direction changes was the result of a thruster-control failure.

“Having mistakenly assessed a thruster-control failure, standard procedures should have prompted ship’s crew to check that the ship was under manual control rather than in autopilot.

“This check did not occur.

“Remaining in autopilot resulted in the ship maintaining a course toward land, until grounding and eventually stranding.”

Rear Admiral Golding said why it happened and what would come next in terms of lessons learned were still being worked on as part of the wider Court of Inquiry, which was expected to be completed in the first quarter of next year.

Rear Admiral Golding said given human error was identified as the cause, a separate disciplinary process would need to be commenced once the Court of Inquiry had concluded.

 

Timeline to disaster:

• On Saturday 5 October 2024, HMNZS Manawanui was conducting survey operations on the southern side of Apia, Samoa, in a strong breeze of up to 25 knots and moderate swell.
• The survey was conducted in a box-shaped area, running east to west in survey lanes that start on the outside, working inwards.
• At about 6.15pm, the ship’s crew attempted a routine turn to starboard, initially to a course of 340 degrees, within the survey area, as part of a turn. The crew attempted to turn off the 340 degree course to starboard towards an easterly course but the ship did not respond as intended.
• Shortly after, Manawanui left the approved survey area, and in an effort to stop the ship, the crew conducted further actions that they believed should have resulted in the ship essentially braking.
• Manawanui did not slow or stop, and instead the ship started to accelerate towards the reef, grounding for the first time at or about 6.17pm at a speed of more than 10 knots.
• The ship then travelled around 635 metres (400 yards) before becoming stranded, grounding multiple times along the way.
• Full control of Manawanui’s propulsion system was not regained until 10 minutes later, at 6.27pm, when the ship’s autopilot was disengaged. The inability to turn the ship to an easterly direction from the 340 degree course and stop the ship is attributed to the ship being in autopilot mode.
• Unsuccessful attempts were then made to manoeuvre the ship off the reef.
• Manawanui was brought to emergency stations after the grounding, and searches were conducted to check for damage.
• No damage or flooding was detected inside the ship. However, stability assessments made after the grounding indicated Manawanui was no longer stable.
• At approximately 6.46pm, about 30 minutes after the initial grounding, the decision was made to abandon ship.
• The timeliness of the decision to abandon ship and to keep Manawanui’s generators running contributed to the successful abandonment process and likely prevented serious injuries or death.
• The ship suffered a series of catastrophic fires after being abandoned, before capsizing and sinking on the morning of Sunday 6 October.

 

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