New life into older flat tops: while the ballistic missile-armed nuclear-powered submarine (SSBN) may have displaced the battleship, the aircraft carrier remains a capital ship: the deployment of six US Navy carriers in support of Operation 'Iraqi Freedom' confirms this assertion.

Today the aircraft carrier comes in all sizes--from the US Navy super carriers of 102.000 tonnes (full load displacement--FLD). with an air group of 80 + aircraft down to Thailand's Chakri Naruebet of 11.485 tonnes FLD with its air group of half-a-dozen former Spanish EAV-8A Harriers. Upgrades tend to come in the form of major subsystems: such as radars, command systems and electronics, or mechanical elements: such as engines, gearboxes or catapult/arresting gear.

Following the sale of the 37-year-old French aircraft carrier Foch, now re-named Sao Paulo, to Brazil in 2000 for under $42 million (FF 300 million at the time), DCN International was contracted to assist the Brazilian Navy (Marinho do Brasil) with its refit.

The main upgrades included fitting a Siconta combat management system to replace the Senit 2 system and an overhaul of the vessel's propulsion system, catapults and arresting gear. In addition, spare parts from Brazil's present carrier, the Minas Gerais, are to be used for minor modifications.

The air group now comprises former Kuwaiti air force A-4KU Skyhawk aircraft (re-designated AF1), while in the future Dassault Super Etendards may be acquired when financial circumstances allow. As the Super Etendard is no longer in production, any aircraft acquired would most likely be former Aeronavale aircraft, to be withdrawn as the Rafale-M enters French service.

Another potential upgrade of major proportions is likely to involve the former Soviet carrier. Admiral Gorshkov, whenever its sale to India is agreed by Russia. year it was announced that India intends to finalise acquisition of the partially gutted vessel. India has been negotiating since 1995 for the Gorshkor, which is being offered for the price of its refit, estimated at between $700 million and $750 million. New Delhi has been unwilling to pay this amount for a vessel that, seriously crippled by a fire, has been lying unused for more than a decade.

The scope and potential cost of the carrier's refit has become controversial in India. The refit will be carried out at the Sevmashpredpriyatie shipyard at Severodvinsk Russia. The ship will emerge as western-style carrier with a free-standing island and a 'ski-jump' of a design prepared by the Nevskoye Design Bureau of St Petersburg, the ship's original designers.

Within the Royal Navy carrier force, the three 20 mm Vulcan Phalanx Mk 19 close-in weapons systems on HMS Invincible and HMS Illustrious were exchanged for the 30 mm Goalkeeper in the early 1990s. At the same time, the ships received Type 996 radar and Type 2016 sonar and Sea Gnat decoys, plus command and control, and support/storage facilities. The HMS Ark Royal retains the 20 mm Vulcan Phalanx.

Between 1998 and 2002, all three carriers received a modification to improve operation of the RAF Harrier GR.7s of the Joint Force Harrier. This involved the removal of the GWS 30 Sea Dart area air defence missile system in the bows with this 18- x 23-metre area being plated-over (giving more deck surface) and the installation of Harrier GR.7 support facilities. The first to receive the re-modelled flight deck was the HMS Illustrious (in a programme costing $ 19.6 million), followed by the HMS Invincible in 1999.

The HMS Ark Royal, which returned to service after its deck and other modifications (described above) in April 2002, became the first Royal Navy ship to operate the Merlin HM.1 helicopter in place of the anti-submarine Sea King HAS.6.

The HMS Invincible is currently completing a refit that includes an upgrade introducing colour displays to its Action Data Automation Weapons System (Adaws). The other two carriers plus the helicopter carrier HMS Ocean (and Type 42 Batch 2 and 3 destroyers) will also receive this upgrade.

Upgrades of this nature to command and control and fire control systems are an evolutionary form of upgrade that may be seen on any naval vessel--including carriers. They are invariably conducted during scheduled periodic refits. Typical of such upgrades are those given to the USS Nimitz during its routine three-year 'Refueling Complex Overhaul', completed in 2001 at the facilities of Newport News Shipbuilding (now part of Northrop Grumman). During the overhaul, the island was significantly upgraded in order to accommodate a new antenna mast and radar tower.

Numerous areas of the superstructure, from levels 05 to 011, were relocated or rearranged, with the top two levels replaced in their entirety, and the main mast was relocated outboard and aft of its original location. The island was also changed from cylindrical to rectangular in shape to take the weight of the new antennas.

The size and shape of the primary flight control area was altered 10 improve the line-of-sight for incoming aircraft, with structural bulkhead modifications to improve fragmentation protection for the new and relocated systems spaces. These included modernised interior and exterior communications plus weapons command and control equipment.

Equipment upgraded in the island and mast included the AN/SPS-48E 3-D and AN/ SPS-49 2-D air-search radars, a Nato SeaSparrow Missile system directors and an EHF radio communications antenna. A new IFF antenna was added and two AN/WSC-6 SHF satellite communications antennas. Changes were made to the Advanced Combat Direction System to allow for Ship Sell Defense System Mk 2 equipment.

The US Navy is also starting to incorporate elements of its Smart Ship programme (currently being put into place on Ticonderoga class Aegis cruisers) on board aircraft carriers.

The USS Harry S Truman, commissioned in 1998, was the first carrier to have Smart Ship integrated bridge technology. The highly automated Litton Marine Systems (formerly Sperry Marine) integrated bridge system. The USS Ronald Reagan, commissioned in 2001, incorporates all digital controls.

Automatic machinery and electronics monitoring, food preparation improvements. reduced bridge manning, improved decking material and paints, more durable and faster equipment and a single PC-based computer system are among the Smart Ship elements to be included on the new carrier.

Seven in-service carriers will be retrofitted with a PC-based fibre-optic local area network. It will replace the current carriers' hybrid systems that feature more than 100 different computer displays connected to myriad workstations and 'stand-alone' systems backed by a mainframe system.

The most recent US Navy carrier upgrade is to be seen in the addition of Raytheon's SSDS Mk 2 Mod 1 to the USS Ronald Reagan planned for next year. It is an integrated distributed architecture, linking the various elements of the carrier's self-defence sensor, weapons and counter-measures systems.

These include Nato SeaSparrow and Rolling Airframe Missiles, the 20 mm Phalanx IB, the AN/SLQ-32A electronic countermeasures system, chaff/flare decoy launchers, onboard sensors including electronic support measures, and the AN/SPQ-9B, AN/SPS-49A(V) and AN/SPS-67(V)1 radars. The SSDS Mk 2 Mod 1 also incorporates IFF and combat identification capabilities.

During trials in November 2002, the SSDS Mk 2 Mod 1 demonstrated its capability against an air threat, responding effectively in manual, semi-automatic and automatic modes. In addition, it demonstrated that it could be effectively linked to an Aegis-equipped ship whilst using Raytheon's Co-operative Engagement Capability.