Cougar Flight 491 plunged into the ocean 55 kilometres east of St. John's on March 12, claiming the lives of the pilot, first officer and 15 offshore workers.

This timeline comes from the Transportation Safety Board (TSB) of Canada, which is investigating the cause of the crash. All times cited are local.

9:18:07 a.m. - Cougar Helicopters Flight 491 departs St. John's. Their heading is 140 degrees (all headings are magnetic).

9:35:52 a.m. - Cougar Flight 491 advises Gander Area Control Centre (ACC) that they have levelled off at 9,000 feet and the estimated time of arrival at the Hibernia platform is 10:10 a.m. Their speed is 204 km/h.

9:45:05 a.m. - Rapid loss of main gearbox oil pressure occurs.

9:55:17 a.m. - Flight data recorder stops recording while the helicopter was about 800 feet above sea level. The helicopter continued to descend in a controlled manner until the tail rotor failed.

9:55:44 a.m. - Tail rotor failure at about 500 feet as the helicopter was descending at about 157 kilometres per hour.

9:55:47 a.m. - Pilot initiates shutdown of both engines, which the TSB describes as "consistent with a tail rotor drive failure emergency."

9:55:54 a.m. - The helicopter nose pitched upwards, which the TSB says is "consistent with a flare for an engines-off landing."

9:56 a.m. - When the helicopter struck the water, it was banking slightly to the right, with its nose up, and at a moderate speed and high rate of descent.

Source: Telegram files and Transportation Safety Board