There have been two major upgrades distinguishing the Adelaide class from the American Oliver Hazard Perry class frigates.
The first three units, as initially constructed, had a length identical at both the main deck and the keel, similar to that of the early Oliver Hazard Perry class ships. From Darwin onwards, the ship's overall length was increased by angling the transom (the section between the fantail and the keel) - this enlarged the flight deck, allowing the larger Seahawk helicopter to be accommodated. This was retrofitted into Adelaide, Canberra and Sydney at their periodic refits.
As part of a major programme of improvements, a AU$1 billion upgrade project for the Adelaide class is in progress, which will see enhancements to both weapons and equipment. The costs of the project will be partly offset by the decommissioning of the two oldest units, with Canberra paying off in 2005, Adelaide is due to be paid off early in 2008. The first upgraded vessel, Sydney, returned to the fleet in 2005. Some of the new features include the ability to fire the SM-2 missile, the addition of an 8 cell Mk 41 VLS for Evolved Sea Sparrow Missile and enhanced air search radar and long range sonar. When these upgrades are complete, the Adelaide class frigates will be the only FFG-7 class ships in the world capable of employing ESSM and SM-2. Each unit to be upgraded will do so at Garden Island in Sydney, with the modifications taking between 18 months and two years. The ships will be replaced starting in 2013 by three new air defence destroyers equipped with the Aegis combat system.
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