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On the afternoon of 13 March 1997, the Royal Australian Naval patrol vessel Fremantle left an anchorage off the Flinders Group of Islands, at the eastern side of Princess Charlotte Bay, and, in company with two other patrol boats following astern, commenced passage for Thursday Island. The vessels followed a planned route utilising the inner route of the Great Barrier Reef at a speed of about 15 knots.

At this time the Australian bulk carrier River Embley was on a south bound loaded passage approaching Piper Reef some 150 miles to the north. River Embley was loaded to a draught of about 12.2 m and while underway, at speeds of between 13 and 14 knots, was drawing about 13.5 m allowing for squat. The navigation was under the direction of a licensed Reef pilot.

At about 2100, the three warships were approaching Heath Reef from the South and River Embley was approaching the reef from the north. The depth of water in the area meant that River Embley was obliged to keep to the eastern side of the two way route and pass about 3 cables off Heath Reef. VHF contact between those on the bridge of HMAS Fremantle and River Embley was established and the message passed that River Embley was a deep draught vessel and the distance the Pilot intended passing off the Reef. The vessels were closing at about 28.5 knots on nearly reciprocal courses with the first two of the three patrol boats crossing ahead of River Embley.

A few minutes after 2100, the lead patrol boat HMAS Fremantle crossed ahead of River Embley, followed by the second vessel in line, the third altered course to pass between River Embley and Heath Reef. HMAS Fremantle made a number of slight alterations and, at about 2108 the rudder was put 20 to starboard. The patrol boat collided with River Embley. There were some slight injuries sustained aboard the patrol vessel as a result of the collision, but nobody on either vessel was seriously hurt. No pollution resulted from the collision.

Damage was sustained to the port side of the patrol boat and some damage was caused to the hull plating close to River Embley's bow and further aft in way of number 3 ballast tank.


These conclusions identify the different factors which contributed to the circumstances and causes of the incident and should not be read as apportioning blame or liability to any particular organisation or individual.

The collision between HMAS Fremantle and the bulk carrier River Embley was caused by the alteration to starboard of HMAS Fremantle when on River Embley's starboard side. The alteration by HMAS Fremantle was made at such a time that, regardless of being constrained by her draught, River Embley could not have taken any action that could have avoided the collision.

The reasons for HMAS Fremantle's actions are the subject of a Naval Board of Inquiry. They involve a complex chain of human factors, which include, but are not limited to:

  • incomplete passage and contingency planning
  • being unaware of the traffic in the reef
  • lack of experience in traffic encounters within the Great Barrier Reef
  • the decision to apply 20 of starboard helm based on incomplete and scanty information.

The absence of the deep draft signals on River Embley cannot be said to have directly contributed to the casualty. The patrol boats were advised that she was constrained by her draught and this was apparently acknowledged. However, had the signals been exhibited, they may have provided an additional prompt for those on Fremantle, as may the use of the Aldis lamp to attract attention had it been easily to hand.

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