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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 was their
complement of two CH-124 Sea King helicopters, which were supported on a
large flight deck with a two-helicopter hangar that collectively took up
roughly half of the ship's available area. The helicopters could be launched
even in high sea states due to their "bear trap" winch system.
The Iroquois represented an original design compromise compared to its
contemporaries. Most ships of the same general size and role, like the Royal
Navy's Type 22 class Frigates or US Navy's Oliver Hazard Perry class FFG's,
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 were able
to carry a complete sensor suite and operate at much longer ranges
independently of the launch ship. This allowed 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 were backed up by two Mk-32 triple
torpedo tubes firing Mk.44 and Mk.46 Mod 5 torpedoes and a Limbo Mark 10
depth charge mortar. For other duties, the ships also mounted an Oto Melara
5-inch / 54-caliber (127/54C) multi-purpose gun and two Mk-29 octuple
launchers with RIM-7 Sea Sparrow for point anti-aircraft defence. These
launchers were located in a protected box on the deck just in front of the
bridge area (behind the gun). For firing, the box opened and the battery
extended to the sides, requiring some time for them to unlimber.
The ships were powered primarily by two Pratt & Whitney FT12-AH3 of 7400
shp each, backed up by two more FT4-A2 gas turbines of 50000 shp each for
boost. They were the first large combat ships to be powered entirely by gas
turbine. The power from these turbines was used to run the twin shafts
through a series of helical gears. One unique feature was the distinctive
Y-shaped "Playboy Bunny" funnels, which were designed to exit the
exhaust gases to either side of the helicopter deck.
Gulf War modification:
HMCS Athabaskan was deployed on Operation Friction, the Canadian Forces
contribution to the international coalition naval task force serving in
Operation Desert Shield and Operation Desert Storm (the Gulf War). Athabaskan
was the flagship of the Canadian Naval Task Group.
She was hurriedly modified at CFB Halifax in August 1990 prior to the
deployment. These modifications included a new mine-avoidance sonar, a
Phalanx 20-mm CIWS (mounted over the Limbo mortar well, which was made
inoperative) and shoulder launched Blowpipe and Javelin missiles.
TRUMP modifications:
As a modernization concept, origins of TRUMP date back to early 1980s. By
mid-80s the Canadian Federal Government had decided on the necessity of
upgrading the Tribal Class ships and released a RFP foreseeing complete
refurbishment. The phrase "update and modernization" essentially
meant stripping down of the vessels to the bare hulls and entire re-equipping
with modern technologies, mechanical or otherwise.
Litton Systems Canada was selected Prime Contractor and Project Manager after
submitting a 4000+ page detailed proposal which emphasized among others,
maximum automation and software engineering in particular. This aspect of the
TRUMP was extremely important due to desired high level of automation in
real-time command and control functions on the refurbished ships. Software
Engineering MIL-STDS being fairly recent and not widely assimilated, Litton
had to exercise particular caution in the area of Software Configuration
Management and Quality Assurance. Litton Proposal to the Canadian Federal
Government had a 250 page SCM and SQA Policies section which was accepted
without a single red-pen due to highly sensitive and farsighted work of
Advance Programs Division Technical Contract Team at Litton who eventually
established a massive and capable engineering force by 1988-89.
The entire class underwent major retrofits in the early 1990s as a part of
the Tribal Class Update and Modernization Project (TRUMP). These refits had
the effect of re-purposing the ships for area air defence; following TRUMP
the Iroquois-class were referred to as air defence destroyers. Their former
anti-submarine role was largely transferred to the Halifax-class frigates.
The main weapon of the new design is the Mk.41 VLS, firing 29 SM-2 Block III
long-range anti-aircraft missiles. To provide room for the VLS, the original
5-in L54 gun was replaced with the smaller, but much faster firing, Oto
Melara 76 mm gun, relocated from the deck to the bridgework above it. A
Phalanx CIWS was also added for self-defence. The torpedo tubes were
retained, but the Limbo and Sea Sparrow systems were removed.
The modernization also replaced the original Pratt & Whitney FFT-12
cruise turbines with newer 12788 shp 570-KF engines from Allison. The speed
remained the same, however, as the weight had increased to 5100 tons full
load. The original split funnel was replaced by a simpler single one, as the
exhaust proved not to be a problem.
The TRUMP was intended to be a stop-gap measure, since the radar systems on
these ships are outdated. Following TRUMP, the Iroquois-class were intended
to be decommissioned by 2010. Defence budget cuts during the mid-1990s
resulted in Huron being left without a crew. Huron was paid off in 2005, and
sunk in a live-fire exercise in 2007 by her sister ship Algonquin.
source: wikipedia
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