The fourth, Henry Larsen was built to a modified design and is considered a subclass, the Improved R-class icebreaker.

[2] The vessel can carry 2,450 m3 (540,000 imp gal) of diesel fuel and has a range of 15,000 nautical miles (28,000 km) at 15 knots (28 km/h) and can stay at sea for up to 120 days.

[5] Classified as a Medium Gulf/River Icebreaker by the Canadian Coast Guard, Henry Larsen was ordered to a modified design from the rest of the class.

The vessel's hull form differs from her classmates, with a differently-shaped bow with a raised forecastle and underwater "ice knife".

Furthermore, the ship has a Wärtsilä air-bubbling system installed to allow the vessel to reduce hull friction and more easily break ice.

Combined, the system creates 12,174 kilowatts (16,326 hp), giving the ship a maximum speed of 16 knots (30 km/h; 18 mph).

Pierre Radisson, the first ship of the class, underwent sea trials while transiting the Northwest Passage en route to Quebec City.

[14] During the transit, Pierre Radisson assisted CCGS Camsell which had been severely damaged by ice in the western Arctic.

While transiting the Northwest Passage, heading to the icebreaker's assigned base in Newfoundland, Franklin lost a propeller in Viscount Melville Sound and was rescued by CCGS Louis S. St-Laurent and returned to the west coast.

[18] In April 1984, after the opening of the navigation season on the Saint Lawrence Seaway and the Great Lakes, the area froze up, driving six cargo ships ashore and a further eighteen became stuck in the ice.

In June 1994, at the height of the Turbot War, Sir John Franklin was among the Coast Guard vessels sent to monitor the European fishing fleets on the Grand Banks.

On the ship's maiden voyage from Victoria, British Columbia to Dartmouth, Nova Scotia, the vessel transited the Northwest Passage, performing sea trials on the trip.

[10][22] As part of the Surface Heat Budget of the Arctic Ocean (SHEBA) experiment in 1997, Louis S. St-Laurent and Des Groseilliers sailed through the Northwest Passage to meet CCGS Sir Wilfrid Laurier in Alaskan waters.