Manufacturer disputes Interislander propeller findings

  • 02/12/2015
A salvage company was brought in to get the propeller off the seafloor (Supplied)
A salvage company was brought in to get the propeller off the seafloor (Supplied)

The cause of the propeller falling off a trouble-plagued Interislander ferry has been found, but manufacturer Wartsila disagrees with the findings.

The Aratere's starboard propeller fell off in Tory Channel during a routine sailing between Picton and Wellington on November 5, 2013.

It managed to get back to Wellington and the propeller was eventually recovered from the sea floor.

The Transport Accident Investigation Commission began an investigation, though it hasn't released its findings yet.

KiwiRail started its own inquiry, commissioning engineering consultancy firm Aurecon to conduct the "lengthy and exhaustive" report.

It points to an "irregularity" in the propeller as the likely cause, but KiwiRail group general manager of network services Todd Moyle says the manufacturer doesn't agree with the conclusion.

The report rules out an external event or a power surge as the causes, and neither was a major lengthening and refurbishment of the vessel in 2011.

"The thoroughness of this investigation has enabled us to be confident in the conclusion of Aurecon's project director, Stephen Jenkins, that all potential factors, other than an irregularity in the propeller itself, are unlikely to have caused this event," Mr Moyle says.

That left four possibilities that could have caused the propeller to fall off:

KiwiRail has reached a confidential agreement with the manufacturer, meaning that though it accepts no liability for the propeller's loss, the state-owned enterprise will continue buying from it.

"KiwiRail uses only reputable recognised suppliers for the critical engineering products that we purchase for our ferries, and this experience means we will be even more vigilant in future."

Mr Moyle says this was an "extremely rare event" and wasn't aware of any similar incidents.

He called for the marine industry manufacturing standards reviewed.

The Atatere is still in service, making six daily trips across the Cook Strait each day.

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