Human Errors in Autopilot System Led to HMNZS Manawanui Disaster

An interim Court of Inquiry report reveals that a critical series of human errors involving the HMNZS Manawanui’s autopilot system led to the disaster. The Royal New Zealand Navy dive and hydrographic ship was lost after a catastrophic grounding incident off the southern coast of Samoa on October 5, 2024, during routine survey operations.

“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,” stated Chief of Navy Rear Admiral Garin Golding.

The incident unfolded over the course of just 12 minutes on the evening of October 5, with the ship operating in challenging conditions including strong winds of up to 25 knots and moderate swells. At approximately 6:15 PM, during what should have been a routine turn to starboard, the crew discovered the vessel wouldn’t respond to course corrections.

The situation quickly deteriorated as the ship left its approved survey area and, despite attempts to halt its progress, accelerated toward the reef at speeds exceeding 10 knots.

In a critical oversight, the crew mistakenly attributed the ship’s unresponsiveness to a thruster control failure, when in fact the vessel remained in autopilot mode. “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,” added Golding.

The Manawanui’s female Captain, British-born Yvonne Gray, has faced intense online harassment over the incident. However, the report commends her decisive action to abandon ship soon after the grounding, at 6:46 PM, which helped save 75 lives.

“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 interim report stated.

The vessel’s fate was sealed in the early hours of October 6, when a series of catastrophic fires led to its capsizing and ultimate sinking. The New Zealand Defence Force has responded with immediate corrective measures, including fleet-wide audits and enhanced training protocols. “I want to reassure the public of New Zealand that we will learn from this situation and that it is on me, as the Chief of Navy, to earn back your trust,” said Golding.

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.