Designed in the late 1960s, the Iroquois were originally designed as a unique solution for long-range anti-submarine warfare. Their primary weapon for this role is their complement of two CH-124 Sea King helicopters, which are supported on a large flight deck with a two-helicopter hangar that collectively takes up roughly half of the ship's available area. The helicopters can be launched even in high sea states due to their "bear trap" winch system.
The Iroquois represents an original design compromise compared to its contemporaries. Most ships of the same general size and role, like the Royal Navy's Type 22 or US Navy's Oliver Hazard Perry, had much smaller helicopter support areas, typically only the rear ¼ of the ship. These supported a single, small, short-range helicopter, the Westland Lynx or Kaman Seasprite. Such small helicopters were incapable of operating independently of the ship's sensors, and were effectively a system for extending the range of the weapons by carrying them away from the ship before launch.
In contrast, the Iroquois and sister ships' much larger Sea Kings are able to carry a complete sensor suite and operate at much longer ranges independently of the launch ship. This allows a single Iroquois to control a much larger area of the ocean, using both its own sensors and those of its helicopters, combining together to scan larger areas. The downside to this design is that the area taken up by the helicopters would normally be given over to other weapon systems.
For anti-submarine use, the helicopters are backed up by two triple-mount torpedo launchers firing Mk.44 and Mk.46 Mod 5 torpedoes and a Limbo Mark 10 depth charge mortar. For other duties, the ships also mount an Oto Melara 5-in multi-purpose gun and two four-round Sea Sparrow launchers for point anti-aircraft defence. These launchers are located in a protected box on the deck just in front of the bridge area (behind the gun). For firing, the box opens and the battery extends to the sides, requiring some time for them to unlimber.
The ships are powered primarily by two Pratt & Whitney FT12-AH3 of 7,400 shp each, backed up by two more FT4-A2 gas turbines of 50,000 shp each for boost. They were the first large combat ships to be powered entirely by gas turbine. The power from these turbines is used to run the twin shafts through a series of helical gears. One unique feature is the distinctive Y-shaped "Playboy Bunny" funnels, which are designed to exit the exhaust gases to either side of the helicopter deck.
The ships are 425 × 50 × 14 feet (129.8 × 15.2 × 4.4 metres) and 5,000 tonnes displacement. The normal crew complement is 285.