Invincible class aircraft carrier

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HMS Invincible
United Kingdom
Builders:	Swan Hunter Vickers Limited Shipbuilding Group
Operators:	Royal Navy
Preceding class:	Audacious class fleet carrier Centaur class light carrier
Following class:	CVF development program
Commissioned:	11 July 1980
Ships in Class
Ships in class:	3
Ships in active service:	HMS Illustrious HMS Ark Royal
Ships in storage:	HMS Invincible
General Characteristics
Displacement:	20,700 tons
Length:	209 m
Beam:	36 m
Draught:	8 m
Propulsion and power:	4 gas turbines 100,000 shp
Speed:	28 knots
Range:	7,000 miles
Complement:
Armament:	2 x 20 mm anti-aircraft guns 3 close-in weapons systems
Aircraft complement:	20 or more, including 16 Harrier and Sea Harrier aircraft 6 Sea King helicopters
Aircraft facilities:	168 m axial flight deck Bow 13° ski ramp

The Invincible-class is a class of aircraft carrier currently serving with the British Royal Navy. There are two vessels of this class in operation (as of November 2006): HMS Illustrious and HMS Ark Royal.

Contents 1 Development 2 Falklands War 3 Modernisation 4 Future 5 Specification 6 Ships in class 6.1 HMS Invincible (R05) 6.2 HMS Illustrious (R06) 6.3 HMS Ark Royal (R07) 7 References

[edit] Development

The Invincible class has its origins in a sketch design for a 6,000 ton guided-missile armed, helicopter carrying escort cruiser intended as a complement to the much larger CVA-01-class fleet aircraft carrier^[1]. The cancellation of CVA-01 in 1966 meant that the smaller cruiser would now have to provide the anti-submarine warfare (ASW) taskforce with command and control facilities. Two new designs were prepared for this requirement^[1]; a 12,500 ton cruiser with missiles forward, six Westland Sea King helicopters and a flight deck aft, somewhat similar to the Vittorio Veneto of the Italian Navy and a larger 17,500 ton vessel with a "through-deck", nine Sea Kings and missiles right forward. By 1970, the "through-deck" design had advanced into a Naval Staff Requirement for an 18,750 ton Through-Deck Command Cruisers (TDCC)^[1].

In February 1963, the Hawker P.1127 VTOL (vertical take-off and landing) aircraft had landed and taken-off from the carrier Ark Royal and the subsequent Hawker-Siddeley Kestrel had undergone trials from the LPH HMS Bulwark. It was therefore perfectly possible that the new ships could be used to operate VTOL aircraft. Politics, however, determined that the new ships were carefully termed "through-deck cruisers" and not "aircraft carrier" by the RN; the cancellation of CVA-01 was intended to mean the UK's abandonment of aircraft carriers for good.

Economic problems in the UK in the early 1970s delayed progress on the new ships, but the design continued to evolve. The order for the first ship was given to Vickers (Shipbuilding) on April 17, 1973^[2]. By now, the design was for a 19,000 ton "CAH"^[1] (helicopter carrying heavy cruiser, styled after the U.S Navy Hull classification symbols) with up to fourteen aircraft and a Sea Dart missile launcher on the bows.

Finally, in May 1975, the Government authorised the maritime version of the Hawker-Siddeley Harrier^{[2] [1]}, which was successfully developed into the Sea Harrier. This meant that the design was reworked again to include a small complement of these VTOL aircraft. In order to launch a heavily-laden Harrier more efficiently by STOVL (short take-off vertical landing) from the comparatively short - 170 m - flight deck, a 'ski-jump' was developed. The slope was initially 7° when incorporated into Invincible and Illustrious and 12° for Ark Royal. The class also has, since 1976^[1], a secondary role as an helicopter carrier, or LPH, in the reinforcement of NATO's Northern flank in Norway. In 1998, HMS Ocean, with a hull form based on that of the Invincibles, was commissioned specifically for this role.

After the 1982 Falklands War, CIWS guns were added to the design. Illustrious had 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.

[edit] Falklands War

Prior to 1982, Invincible's air group consisted purely of Sea King HAS.5 anti-submarine helicopters and Sea Harrier FRS.1 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.

[edit] 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. 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 Merlin 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.

[edit] Future

The Sea Harrier officially retired on 1 April 2006, having gone 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 Fleet Air Arm 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 are brought into service. They are expected to displace around 60,000 tonnes each - three times the displacement of the Invincible class.

[edit] Specification

• Length: 689 ft (210 m)
• Beam: 118.1 ft (36 m)
• Draught: 28.9 ft (8.8 m)
• Displacement: 16,970 tons standard; 20,710 tons full load
• Crew: c. 1,000 (131 officers, 265 senior rates, 604 junior rates) excluding aircrew and embarked military force of c. 500
• Power: 4 x 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

[edit] Ships in class

[edit] References

1. ^ ^{a b c d e f} Vanguard to Trident; British Naval Policy since World War II, Eric J. Grove, The Bodley Head, 1987, ISBN 0-370-31021-7
2. ^ ^{a b} Warships of the Royal Navy, Capt. John E. Moore RN, Jane's Publishing, 1981, ISBN 0-7106-0105-0

Invincible-class aircraft carrier

Invincible | Illustrious | Ark Royal

List of aircraft carriers of the Royal Navy