Invincible Class Aircraft Carriers - Development

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. 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; 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).

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 "Commando carrier" (an aircraft carrier operating helicopters) HMS Bulwark. It was therefore perfectly possible that the new "cruisers" could be used to operate VTOL aircraft. The new ships were called "through-deck cruisers" and not "aircraft carrier". This was in part because CVA-01's cancellation was so recent, but also because the ships were intended to serve in traditional cruiser roles of C3I and anti-submarine warfare, and were constructed like cruisers.

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 17 April 1973. By now, the design was for a 19,000 ton "CAH" (helicopter carrying heavy cruiser, styled after the US Navy hull classification symbols) with up to fourteen aircraft and a Sea Dart missile launcher on the bows.

The government decided that the carrier needed fixed-wing aircraft to defend against Soviet reconnaissance aircraft. In May 1975, it authorised the maritime version of the Hawker Siddeley Harrier, 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, 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 Invincible class, 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 were replaced with three Goalkeeper systems. Ark Royal has the three Phalanx CIWS systems she was fitted with when built (she can be easily distinguished from her sisters by the 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.