The Loch class was designed to meet the requirement for large numbers of long-range escorts for the Royal Navy.

They were a development of the earlier River class, but designed for mass production, with pre-fabricated sections to be built by general engineering companies and assembled at shipyards.

[5] Sufficient fuel was carried to give a range of 4,800 nautical miles (8,900 km; 5,500 mi) at 15 knots (28 km/h; 17 mph) in tropical waters.

[11][12] In February 1944, it was decided to loan Loch Achanalt to the Royal Canadian Navy, and the ship was commissioned on 31 July 1944 after initial sea trials.

[1][10] On 16 October, the 6th Canadian Escort Group was deployed South-West of the Faroe Islands to stop German submarines from getting into the North Atlantic from bases in Norway.

[13][14] In November–December 1944, Loch Achanault was fitted with additional bracing to rectify problems with hull stiffness that the class suffered with.

From 14 March to 20 April, the group were deployed from Plymouth to the English Channel and South-Western Approaches on convoy defence duties.

[17] Loch Achanalt then sailed back to Britain, and was reduced to reserve at Sheerness in June before formally being returned to the Royal Navy in July.

[1] Pukaki alternated with an American Edsall-class DER picket frigate operating from Dunedin in summer months to track United States Navy Lockheed C-130 Hercules deployments and other flights from Harewood airport in Christchurch to McMurdo Base in the Ross Dependency, offering the potential for search and rescue in the Southern Ocean and service to the weather station on Campbell Island.

Sea conditions probably shortened by two years the service life of Pukaki and the other surviving Loch-class frigate, Rotoiti.