The flagship of Canada's fleet of icebreakers will be going south for repairs after suffering mechanical problems during a scientific mission in the Arctic Ocean.

The Louis St. Laurent was working in the thick ice on Sept. 19 when crew members felt an abnormal vibration in the stern.

"Upon further investigation with its autonomous underwater vehicle, it was determined there was a problem with the centre propeller," said Brian LeBlanc, the Coast Guard's fleet director for the Arctic.

The 42-year old icebreaker was on a joint mission with the U.S. Coast Guard to continue surveying and mapping the continental shelf beyond 200 nautical miles for Canada's submission to the Commission on the Limits of the Continental Shelf under the United Nations Convention on the Law of the Sea.

When the St. Laurent broke down, the U.S. Coast Guard cutter Healy escorted it out of the ice.

From there the icebreaker sailed eight days under its own power to Cambridge Bay, Nunavut, where it has sat offshore since Sept. 27.

Repairs needed

"Unfortunately the on-site repairs were not successful, so we're faced with bringing the ship through the Northwest Passage and down to the south where we can put it into dry dock to complete the repair," said LeBlanc.

The St. Laurent has two working propellers to make the voyage.

LeBlanc says the scientific mission in the Arctic Ocean was completed before the breakdown, and the ship was then scheduled to be on stand-by for icebreaking duties in the high Arctic until its return to St. John’s, N.L., in mid-November.

There are other Coast Guard ships around Nunavut that will pick up the St. Laurent’s duties.

The St. Laurent is scheduled to be replaced in 2017 by a new $720 million polar-class icebreaker that will be named the John G. Diefenbaker.