New Spirit ferries not using autopilot near Geelong after steering faults

The two new Spirit of Tasmania ferries have suffered separate steering faults near Geelong in recent weeks.

Operator TT-Line has revealed the ships are no longer using autopilot during their transit of Port Phillip Bay.

The Australian Transport Safety Bureau is investigating the steering incidents, with a report due by the middle of next year.

The operator of the new Spirit of Tasmania ferries has suspended autopilot use during transits of Port Phillip Bay as it probes the ships' steering faults.

Spirit IV was on its fifth-ever passenger voyage last Thursday when its primary steering system failed as it neared the bay en route to Geelong.

The issue occurred when the steering control was switched from autopilot to manual mode.

A back-up steering system ended up being used, and a tugboat was called to escort the ferry to Geelong, delaying its scheduled arrival by about four hours.

The incident came after a separate steering fault caused its sister ship, Spirit V, to briefly move outside the bay's charted shipping lane during a trial voyage in October.

Both matters are now under investigation by the Australian Transport Safety Bureau.

On Monday, TT-Line chairman Ken Kanofski said last week's incident on Spirit IV involved a "frustratingly minor issue".

"There's an ongoing investigation, and I don't want to prejudice that by kind of declaring exactly that everything's been dealt with," Mr Kanofski told 936 ABC Hobart.

"When Spirit IV docked in Geelong, an inspection found a frustratingly minor issue with mechanical electrical processes in the steering console itself.

Mr Kanofski said the autopilot, which allows a ship to automatically follow a pre-determined route, is no longer being used when approaching and departing Geelong.

"So at the moment, we're not using autopilot in the bay, in Geelong, in Port Phillip Bay," Mr Kanofski said.

However, the autopilot will still be used once the ship reaches the open waters of Bass Strait, he said.

Mr Kanofski said the autopilot was never used for the ferries' arrival and departure at Devonport, in Tasmania's north-west.

"Obviously in Geelong you come in through the heads, and you've got quite a long way to navigate to get to port.

"In Devonport it's a very short distance, and so that's always been a completely manual process.

"But we've taken a range of interim measures to ensure that the ships and the passengers are safe, and that's our number one priority here."

The ABC has asked TT-Line when it plans to resume its use of autopilot during transits of Port Phillip Bay.

On Sunday, Spirit IV conducted an exercise off Devonport that was described by TT-Line as a "planned, routine check of its equipment".