On 21 Dec 1974 a storm formed over the warm waters of the Arafura Sea, and began to move south westwards, picking up more energy as it went. After a previous cyclone false alarm c 10 days before, the people of Darwin werent overly concerned. On 24 Dec, the storm picked up strength and veered around to the south east and converged on Darwin late on Christmas Eve.
Cyclone Tracy destroyed more than 70% of Darwins buildngs and killed over 70 people.
The Australian Government swung into action and deployed the armed forces as part of a relief operation. Nine Wessex of HS-817 helped move people and equipment while other parts of the relief work involved evacuating people from Darwin while the town was essentially rebuilt. The RAN withdrew at the end of Jan 1975 and handed over to the local Army commander for the remainder of the work.