Invincible class aircraft carrier

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Invincible-class aircraft carrier
Image:HMS Invincible.jpg
Class Overview
Class Type	Aircraft carrier
Launched	1977–1981
Preceded By	Audacious-class aircraft carrier Centaur-class aircraft carrier
Succeeded By	CVF
Ships of the Class:	Invincible (R05) Illustrious (R06) Ark Royal (R07)

The Invincible-class aircraft carrier is a design currently in use by the Royal Navy. There are two carriers of this class in operation HMS Illustrious (R06, 1982) and HMS Ark Royal (R07, 1985) (initially planned as Indomitable).

1 Development
2 Armament
3 Falklands
4 Modernisation
5 Future
6 Specification
7 Ships in class

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Development

The original class design was for a 12,500 tonne anti-submarine escort carrier as a complement to the much larger CVA-01 fleet carrier project. The CVA-01 was cancelled in 1966 and the escort carrier design was reworked for a ASW cruiser with six helicopters and command capability. The helicopter complement was then increased to nine and the vessel was again redesigned into a 19,500 ton carrier. Politics determined that they were carefully termed 'through-deck cruisers' not 'aircraft carrier' by the RN: the cancellation of CVA-01 was intended to mean the UK's abandonment of aircraft carriers for good. The successful development of the Sea Harrier meant that the design was reworked again to include a small complement of these STOVL aircraft. In order to launch the Harrier from its comparatively short flight deck of 170 m, a 'ski-jump' was incorporated, with the slope initially set at 7° for Invincible and Illustrious and 12° for Ark Royal. The class also has a secondary role as an helicopter carrier, or LPH, in the reinforcement of NATO's Northern flank in Norway. HMS Ocean, with a hull form based on the Invincible class design, was commissioned in 1998 for this role.

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Armament

The ships are armed with a variety of weapons. As built, they had two 20 mm Oerlikon GAM-B01 guns, which they retain, and the Sea Dart surface-to-air missile mounted on the forecastle. Because of lessons learnt during the 1982 Falklands War, CIWS guns were added to the design. Illustrious having them fitted at the last minute before commissioning, Ark Royal had them added as a normal part of the building process, and Invincible had them fitted during her first overhaul after the Falklands. Initially, Invincible and Illustrious were fitted with two Vulcan Phalanx units; these have since been replaced with three Goalkeeper systems. Ark Royal on the other hand has the three Phalanx CIWS systems she was fitted with when built (she can be easily told from her sisters by Phalanx's distinctive white "R2-D2" radome). Electronic countermeasures are provided by a Thales jamming system and ECM system. Seagnat launchers provide for chaff or flare decoys. As part of upgrades during the mid 1990s, all three ships had the Sea Dart removed, with the forecastle filled in to increase the size of the flight deck.

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Falklands

Prior to 1982, Invincible's air group consisted purely of Sea King HAS1 anti-submarine aircraft and Sea Harrier FRS1 aircraft. Typically, nine Sea Kings, and four or five Sea Harriers were embarked. This was due to the fact that the originally envisioned mission for the ships was to provide the heart of ASW hunter-killer groups in the North Atlantic during a war against the Soviet Union. In that context, the main weapon of the carrier would not be its fighter aircraft, but its ASW helicopters. The fighters were on board to shoot down the occasional Soviet maritime patrol aircraft nosing around the ship and its escorts.

The Falklands War changed all of that, since it proved that Britain still needed to retain the capability to use carrier air power in its traditional role of power projection, both over land, and against enemy fleets (the Falklands nearly saw the first carrier vs carrier battle since WWII). The Falklands had seen Invincible, and the other aircraft carrier deployed, the larger and older HMS Hermes filled to the gunwales with both the Sea Harrier, and the Royal Air Force Harrier GR3 ground attack variant of the aircraft, along with ASW helicopters. The RAF Harriers proved to be a temporary aberration at the time, but a permanent addition to the usual air group was made due to lessons learnt during the war. That addition was a new type of Sea King, an Sea King AEW2A (Airborne Early Warning) version. Illustrious carried the first examples of the type when it was rushed south in the aftermath of the Falklands to relieve Invincible of its guard duty around the islands.

In the aftermath of the Falklands, the typical air group was 3 AEW Sea Kings, 9 ASW Sea Kings and 8 or 9 Sea Harriers. Analysis of the Sea Harrier's performance during the war lead to the requirement for an upgrade, approval for which was granted in 1984. Initially to be known as the FRS.2, the Sea Harrier FA2 entered service on April 2 1993, deploying on Invincible to Bosnia in 1994. The FA2 features the Blue Vixen radar which is described as one of the most advanced pulse Doppler radars in the world. The Blue Vixen formed the basis for the Typhoon's CAPTOR radar. The FA2 carries the AIM-120 AMRAAM. The final new-build Sea Harrier FA2 was delivered on January 18, 1999. Other improvements were made to the class during the 1980s and early 1990s, with probably the most important being the increase of the ski jump angle on Invincible and Illustrious to match the 12° slope of Ark Royal.

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Modernisation

In more recent years, three other changes have been made. One was the removal of the Sea Dart system, creating an increased deck park for aircraft, making the ships look a great deal more like pure aircraft carriers than the hybrid cruiser / aircraft carrier form in which they were originally built. It is quite surprising how much the removal of the SAM system and its associated fire control radars alters the lines of the ships. The Sea Dart magazines were converted to increase air-to-surface weapons stowage, and new aircrew briefing facilities created under the extended flight deck, both to support the embarkation of RAF Harrier GR7s as a routine part of the air group. The ships have all also been fitted to handle the new Merlin helicopters. The HM1 variant of the Merlin has replaced the HAS6 variant of the Sea King in the carrier-borne ASW role. Since the integration of the Harrier GR7, typical deployments have included 7 or 8 of those aircraft, pushing the Merling onto the carrier's escorting Fort class replenishment ship.

The two most recent wartime deployments of the class have seen them in their secondary LPH role, as it was officially judged that Sea Harriers could provide no useful role in the missions. During those deployments, the class has embarked RAF Chinook helicopters, in lieu of their fixed wing complement.

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Future

The Sea Harrier retires on 1st April 2006, and went to sea for the last time in October 2005. From now until the decommissioning of the ships, their principal weapon will be the Harrier GR9 flown by two FAA and two RAF squadrons. Invincible was decommissioned in July 2005, and has been mothballed (available for reactivation on notice) until 2010. Illustrious has taken over as the Flagship and is planned to decommission in 2012, and Ark Royal in 2015, as two new, much larger future Royal Navy carriers. They are expected to displace around 60,000 tonnes each - three times the displacement of the Invincible class. Rumours that one of the Invincibles upon decommissioning will be converted into a full-time LPH to complement Ocean should be discounted because of the expense of running an aging, crew-intensive Invincible, and the limitations of the design in such a role.

The ships have given fine service to the Royal Navy during their careers, despite the inherent limitations of the design. Invincible played a large part in winning the largest naval war since WWII, and they have kept Royal Navy fixed wing aviation alive through a very lean period.

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Specification

Length: 209 m
Beam: 36.1 m
Draught: 8.4 m
Displacement: 20,400
Crew: around 1000 including aircrew, can carry an extra 500 soldiers
Power: 4 of Rolls-Royce Olympus gas turbines (COGAG) 100,000 shp (75 MW), 8 Paxman Valenta diesel generators.
Speed: 28 knots, 18 knots cruising
Range: 7000 nm at 18 knots

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