Prestonian-class Frigates Cold War ASW Escorts

The Prestonian-class ocean anti-submarine escort frigate was a specialized class of 21 vessels that served as a critical component of the Royal Canadian Navy (RCN) from 1953 to 1967, and the Royal Norwegian Navy from 1956 to 1977. These ships were not built from scratch but were converted from mothballed River-class frigates of British design, which had been placed in reserve after the conclusion of the Second World War.

Historical Context and Strategic Need

During the Korean War era, Canada's commitment to the North Atlantic Treaty Organization (NATO) highlighted a growing strategic threat. The Soviet Union's submarine technology was advancing rapidly, making their vessels increasingly difficult to detect and identify. This posed a significant risk to the vital shipping lanes supplying the European continent.

In response, Vice-Admiral H.T.W. Grant, Chief of the Naval Staff of Canada, pledged that Canada would provide anti-submarine escort forces to counter this threat. While the initial plan was to update the existing fleet, the policy expanded to include the conversion of 21 decommissioned River-class frigates into modernized ocean escorts.

Technological Innovations and Modifications

To meet the demands of post-war naval warfare and the specific threat of Soviet submarines, the River-class design underwent extensive modifications:

• Habitability and Space: The fo'c'sle deck was extended aft and wall-sided, providing improved living conditions for the crew, including individual bunks.
• Power Generation: Machinery was updated from three steam and one diesel generator to two steam and two diesel generators to support new ASW equipment.
• Structural Changes: A larger, almost entirely enclosed bridge structure was installed. To offset the weight, aluminum was used for the upper works instead of steel. This required a heightened funnel and a larger tripod mast.
• Hull Strengthening: The forward hull was strengthened to provide better protection against ice during North Atlantic operations.
• Armament: The quarterdeck was enclosed to accommodate two Squid anti-submarine mortars.

Helicopter Trials

Canada pioneered the concept of operating anti-submarine warfare helicopters from escort decks. HMCS Buckingham was equipped with a helicopter flight deck at her stern for sea trials conducted between October and December 1956. These trials were instrumental in the subsequent design of the Royal Canadian Navy's destroyer helicopter carriers.

International Service and Other Roles

The class saw limited international export. In 1956, three frigates—HMCS Prestonian, HMCS Penetang, and HMCS Toronto—were loaned to the Royal Norwegian Navy and renamed Troll, Draug, and Garm. These were purchased outright by Norway in 1959.

Additionally, three River-class frigates (HMCS Stone Town, HMCS St. Catharines, and HMCS St. Stephen) were disarmed and transferred to the Department of Transport of Canada to serve as weather ships, though they retained their RCN pennant numbers and are generally considered part of the class.

Technical Specifications