A fully loaded bulk carrier narrowly avoided disaster when its rudder completely broke off during departure from a New Zealand port, highlighting critical failures in maintenance procedures that could have implications for global maritime safety standards.

On July 24, 2023, the Achilles Bulker was under pilotage outbound from the Port of Tauranga when its heading began to swing unexpectedly to port. As the bridge team attempted corrective action, the ship’s rudder completely separated from the vessel, causing it to drift out of the channel toward shallow waters.

Quick action by the pilots and crew, who successfully deployed both anchors, prevented what could have been a serious grounding incident.

The Transport Accident Investigation Commission (TAIC) investigation determined that “the rudder pintle was missing, which left the bottom of the rudder unsupported and allowed excessive movement in the rudder system.” This critical component—essentially a heavy hinge pin that allows the rudder to turn while supporting it—had dropped out of position before the final catastrophic failure.

Investigators traced the problem to a 2021 dry dock maintenance period when “the rudder pintle assembly was removed and later reinstalled.” The Commission concluded it is “virtually certain that the way the rudder pintle assembly was reinstalled did not ensure that the pintle would remain in place during normal shipboard operations.”

The failure mechanism was detailed in the investigation: “With its securing parts broken, the nut that retained the pintle as part of the rudder assembly unwound itself. Sometime before the incident off Tauranga, the pintle dropped unnoticed from its casting and sank”. Without proper support, “the rudder increasingly moved side to side and fore and aft,” placing excessive forces on the rudder palm until fatigue cracks developed and the entire rudder detached.

TAIC emphasized that “pintles are critical components of a critical system and should be treated as such,” noting that proper installation is “important for the durability of the rudder system and for preventing loss of the pintle and rudder.”

The Commission has made two formal recommendations: first, that the shipyard implement “robust quality assurance procedures for rudder pintle installation,” and second, that Maritime NZ work with the International Maritime Organisation to “promote enhanced global standards for quality assurance of rudder systems during installation, maintenance, and repairs.”

This incident serves as a stark reminder that “the loss of controlled maneuverability of a ship is particularly dangerous when navigating in pilotage waters,” and that “pilots and ship crews need to be prepared for such an event.”

You can find the full investigation report here.

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