Aircraft carrier

Two aircraft carriers, USS John C. Stennis (left), and HMS Illustrious (right), showing the difference in size between a supercarrier and a light V/STOL aircraft carrier.

The Russian aircraft carrier Kuznetsov.

The French aircraft carrier Charles de Gaulle.

An aircraft carrier is a warship whose main role is to deploy and recover aircraft—in effect acting as a sea-going airbase. Aircraft carriers thus allow a naval force to project air power great distances without having to depend on local bases for land-based aircraft. Modern navies who operate such ships, treat aircraft carriers as the centerpiece of the fleet, a role previously played by the battleship. The change, part of the growth of air power as a significant part of warfare, took place during World War II. Unescorted carriers are considered vulnerable to attack by other ships, aircraft, submarines or missiles and therefore travel as part of a carrier battle group. In many navies, especially the United States Navy, an aircraft carrier is a capital ship.

Flight deck configuration

Modern aircraft carriers have a flat-top deck, the flight deck that serves as a take-off and landing area for aircraft. Aircraft take off to the front, into the wind, and land from the rear. Carriers steam at speed, for example up to 35 knots (65 km/h), into the wind during take-off in order to increase the apparent wind speed, thereby reducing the speed of the aircraft relative to the ship. On some ships, a steam-powered catapult is used to propel the aircraft forward assisting the power of its engines and allowing it to take off in a shorter distance than would otherwise be required, even with the headwind effect of the ship's course. On other carriers, aircraft do not require assistance for take off — the requirement for assistance relates to aircraft design and performance. Conversely, when landing on a carrier, some aircraft rely upon a tailhook that catches on arrestor wires stretched across the deck to bring them to a stop in a shorter distance than normal. Other aircraft utilise their hover capability to land vertically and so require no assistance in speed reduction upon landing. Since the end of World War II it has been common to direct the landing recovery area off to port at an angle to the line of the ship. The primary function of the angle deck landing area is to allow aircraft who miss the arresting wires, refered to as a "bolter", to become airborne again without the risk of hitting aircraft parked on the forward parts of the deck. The angle deck also allows launching of aircraft at the same time as others land.

The above deck areas of the warship (the bridge, flight control tower, engine exhausts and so on) are concentrated to the starboard side of the deck in a relatively small area called an "island". Very few carriers have been designed or built without an island and such a configuration has not been seen in a fleet sized carrier.

A more recent configuration, used by the Royal Navy, has a 'ski-jump' ramp at the forward end of the flight deck. This was developed to help launch VTOL (or STOVL) aircraft (aircraft that are able to take off and land with little or no forward movement) such as the Sea Harrier. Although the aircraft are capable of flying vertically off the deck, using the ramp is more fuel efficient. As catapults and arrestor cables are unnecessary, carriers with this arrangement reduce weight, complexity, and space needed for equipment.

Common types

Over the course of the last century there have been several types of aircraft carrier, some of which are now obsolete. They can be generally categorised as follows:

Initial designs and inter-war developments

• Seaplane tenders, such as HMS Engadine, out of frontline use after the 1920s when carriers capable of handling conventional airplanes came into fleets and the superiority of landplanes over seaplanes in naval operations became firmly established.
• Standard carriers, such as HMS Ark Royal, typically 20,000 to 65,000 tons. Often known as "fleet carriers."
• Flying aircraft carrier; airship that can carry aircraft. Example include USS Akron and Macon

World War II developments

• Escort carriers, such as USS Barnes, were built only during World War II, and were used by the Royal Navy and U.S. Navy.
• Light aircraft carriers, such as USS Independence, were designed to primarily carry fighters.
• CAM ships, such as SS Michael E, cargo carrying merchant ships which could launch but not retrieve fighter aircraft. These vessels were an emergency measure during World War II.
• Merchant aircraft carriers (MACs), such as MV Empire MacAlpine, another emergency measure which saw cargo-carrying merchant ships equipped with flight decks.
• Carrier battleships were created by the Imperial Japanese Navy to partially compensate for the loss of carrier strength at Midway. Two of them were made from Ise class battleships. The aft turrets were removed and replaced with a hangar, deck and catapult.
• Submarine aircraft carriers, such as the French Surcouf, or the Japanese I-400 class submarines which were capable of carrying 3 Aichi M6A Seiran aircraft. The first of these were built in the 1920s.

In addition, many battleships, cruisers and merchant raiders were equipped with floatplanes for reconnaissance.

Post-war developments

• Amphibious assault carriers, such as USS Tarawa, which often also serve the purpose of carrying and landing soldiers and operate a large contingent of helicopters for that purpose. Also known as "commando carriers" or "helicopter carriers."
• Anti-submarine warfare carriers, such as HMS Ocean, also known as "helicopter carriers."
• Supercarriers, such as USS Nimitz, typically 75,000 tons or greater.

Some cruisers and capital ships of the inter-war years often carried a catapult launched seaplane for reconnaissance and spotting the fall of the guns. It was launched by a catapult and recovered by crane from the water after landing. These were mostly removed during World War II, but had some notable successes early in the war as shown by HMS Warspite’s Walrus during operations in the Norwegian fjords in 1940.

Many modern warships have helicopter landing capability and helicopter assault ships represent a new form of amphibious assault carrier.

History and milestones

Genesis

As heavier-than-air aircraft developed in the early 20th century various navies began to take an interest in their potential use as scouts for their big gun warships. A number of experimental flights were made to test the concept. Eugene Ely was the first pilot to launch from a stationary ship in November 1910. He took off from a structure fixed over the forecastle of the US armoured cruiser USS Birmingham at Hampton Roads, Virginia and landed nearby on Willoughby Spit after some five minutes in the air. On January 18, 1911 he became the first pilot to land on a stationary ship. He took off from the Tanforan racetrack and landed on a similar temporary structure on the aft of USS Pennsylvania anchored at the San Francisco waterfront—the improvised braking system of sandbags and ropes lead directly to the arrestor hook and wires described above. His aircraft was then turned around and he was able to take off again. Commander Charles Samson, RN, became the first airman to take off from a moving warship on May 2, 1912. He took off in a Short S27 from the battleship HMS Hibernia while she steamed at 10.5 knots (19 km/h) during the Royal Fleet Review at Weymouth.

HMS Ark Royal was the first aircraft carrier. She was originally laid down as a merchant ship, but was converted on the building stocks to be a seaplane carrier. Launched in 1914, she served in the Dardanelles campaign and throughout World War I.

The first strike from a carrier against a land target took place on July 19, 1918. Seven Sopwith Camels launched from HMS Furious attacked the German Zeppelin base at Tondern, with two 50 lb bombs each. Several airships and balloons were destroyed, but as the carrier had no method of recovering the aircraft safely, two of the pilots ditched their aircraft in the sea alongside the carrier while the others headed for neutral Denmark.

The inter-war years

The Washington Naval Treaty of 1922 placed strict limits on the tonnages of battleships and battlecruisers for the major naval powers after World War I, as well as limits not only on the total tonnage for carriers, but also an upper limit on 27,000 tonnes for each ship. Although exceptions were made regarding the max ship tonnage (fleet units counted, experimental units did not), the total tonnage could not be exceeded. However, while all of the major navies were over-tonnage on battleships, they were all considerably under-tonnage on aircraft carriers. Consequently, many battleships and battlecruisers under construction (or in service) were converted into aircraft carriers. The first ship to have a full length flat deck was HMS Argus the conversion of which was completed in September 1918, with the U.S. Navy not following suit until 1920, when the conversion of USS Langley had completed. The first American fleet carriers would not join the service until 1928 ( USS Lexington and Saratoga).

The first purpose-designed aircraft carrier to be developed was the HMS Hermes, although the first one to be commissionned was the Japanese Hosho (commissioned in December 1922, followed by HMS Hermes in July 1923). Hermes' design preceded and influenced that of the Hosho, and its construction actually began earlier, but numerous tests, experiments and budget considerations delayed its commission.

By the late 1930s, aircraft carriers around the world typically carried three types of aircraft: torpedo bombers, also used for conventional bombings and reconnaissance; dive bombers, also used for reconnaissance (in the U.S. Navy, this type of aircraft were known as "scout bombers"); and fighters for fleet defence and bomber escort duties. Because of the restricted space on aircraft carriers, all these aircraft were of small, single-engined types, usually with folding wings to facilitate storage.

The Second World War

Aircraft carriers played a significant role in World War II. With seven aircraft carriers afloat, the Royal Navy had a considerable numerical advantage at the start of the war as neither the Germans or the Italians had carriers of their own. However, the vulnerability of carriers to traditional battleships was quickly illustrated by the sinking of HMS Glorious by German battlecruisers during the Norwegian campaign in 1940. By World War II, seaplane carriers were no longer considered to be equals to carriers which could operate conventional aircraft, as conventional planes could fly farther, faster, with heavier weapons loads and greater performance; by the end of the war, early helicopters were taking over many of the roles of seaplanes.

This apparent weakness to battleships was turned on its head in November 1940 when HMS Illustrious launched a long-range strike on the Italian fleet at Taranto. This operation incapacitated three of the six battleships in the harbour at a cost of two of the 21 attacking Fairey Swordfish torpedo bombers. Carriers also played a major part in reinforcing Malta, both by transporting planes and by defending convoys sent to supply the besieged island. The use of carriers prevented the Italian Navy and land-based German aircraft from dominating the Mediterranean theatre.

In the Atlantic, aircraft from HMS Ark Royal and HMS Victorious were responsible for slowing Bismarck during May 1941. Later in the war, escort carriers proved their worth guarding convoys crossing the Atlantic and Arctic oceans.

Many of the major battles in the Pacific involved aircraft carriers. Japan started the war with ten aircraft carriers, the largest and most modern carrier fleet in the world at that time. There were six American aircraft carriers at the beginning of the hostilities, although only 3 of them were operating in the Pacific.

Drawing on the 1939 Japanese development of low-depth runs for aerial torpedoes, and the 1940 British aerial attack on the Italian fleet at Taranto the 1941 Japanese surprise attack on Pearl Harbor was a clear illustration of the power projection capability afforded by a large force of modern carriers. Simultaneously, the Japanese began their advance through South East Asia and the sinking of Prince of Wales and Repulse by Japanese land-based aircraft drove home the need for this ship class for fleet defence from aerial attack. In April 1942, the Japanese Fast Carrier Strike Force ranged into the Indian Ocean and sank shipping, including the under-repair and undefended carrier HMS Hermes. Smaller Allied fleets with inadequate aerial protection were forced to retreat or be destroyed. In the Coral Sea, US and Japanese fleets traded aircraft strikes in the first battle where neither side's ships sighted the other. At the Battle of Midway four Japanese carriers were sunk in a surprise attack by planes from three American carriers and this is considered to be the turning point of the war in the Pacific.

Subsequently the US was able to build up large numbers of aircraft aboard a mixture of fleet, light and (newly commissioned) escort carriers. These carriers played a major part in winning the Pacific war. The eclipse of the battleship as the primary component of a fleet was clearly illustrated by the sinking of the largest battleship ever built, Yamato, by carrier-borne aircraft in 1945. Japan also built the largest aircraft carrier of the war, Shinano, which, like Yamato, was named after a Japanese province.

Wartime innovations

Combat experience proved that the British invention of the sealed "hurricane bow" which protected against storms was superior to any other use for the very front of the ship, be it machine-guns or a second flight deck. This became standard for British and American carriers. The Japanese carrier Taiho was the first of their ships to incorporate it.

Starting late in the war with the Midway class, American carriers had grown so large that it was no longer practical to continue the concept of designing the hangar deck to be the strength deck, and all subsequent American carriers have the flight deck as the strength deck, leaving only the island as superstructure.

Light Aircraft Carriers

The loss of three major carriers in quick succession in the Pacific led the US Navy to develop the light carrier (CVL) from light cruiser hulls that had already been laid down. These were intended to add fighter squadrons to a task force, and were used in the US Navy only during World War II. The Royal Navy made a similar design which served both them and Commonwealth countries after World War II. One of these carriers, India's INS Viraat, formerly HMS Hermes, is still being used.

Escort Carriers and Merchant Aircraft Carriers

To protect Atlantic convoys, the British developed what they called Merchant Aircraft Carriers, which were merchant ships equipped with a flat deck for half a dozen aircraft. These operated with civilian crews, under merchant colors, and carried their normal cargo besides providing air support for the convoy. As there was no lift or hangar, aircraft maintenance was limited and the aircraft spent the entire trip sitting on the deck.

These served as stop-gap until dedicated escort carriers could be built in the US (US classification CVE). About a third of the size of a fleet carrier, it carried about two dozen aircraft for anti-submarine duties. Over one hundred were built or converted from merchantmen.

Escort carriers were built in the US from two basic hull designs: one from a merchant ship, and the other from a slightly larger, slightly faster tanker. Besides defending convoys, these were used to transport aircraft across the ocean. Nevertheless, some participated in the battles to liberate the Philippines, notably the battle off Samar in which six escort carriers and their escorting destroyers briefly took on five Japanese battleships and bluffed them into retreating.

Catapult Aircraft Merchantmen

As an emergency stop-gap before sufficient merchant aircraft carriers became available, the British provided air cover for convoys using Catapult aircraft merchantman (CAM ships) and merchant aircraft carriers. CAM ships were merchant vessels equipped with an aircraft, usually a battle-weary Hawker Hurricane, launched by a catapult. Once launched, the aircraft could not land back on the deck and had to ditch in the sea if it was not within range of land. Over two years, fewer than 10 launches were ever made, yet these flights did have some success: 6 bombers for the loss of a single pilot.

The Angled Deck

During the Second World War, aircraft would land on the flight deck parallel to the long axis of the ship's hull. Aircraft which had already landed would be parked on the deck at the bow end of the flight deck. A crash barrier was raised behind them to stop any landing aircraft which overshot the landing area because its landing hook missed the arrestor cables. If this happened, it would often cause serious damage or injury and even, if the crash barrier was not strong enough, destruction of parked aircraft.

An important development of the 1940s was the British invention of the angled deck, where the runway was canted at an angle of a few degrees across the ship. If an aircraft misses the arrestor cables, the pilot only needs to increase engine power to maximum to get airborne again and will not hit the parked aircraft because the angled deck points out over the sea. The picture of USS John C. Stennis at the top shows an angled landing deck.

Post-War Developments

The modern steam-powered catapult, powered by steam from the ship's boilers or reactors, was invented by Commander C.C. Mitchell RNVR. It was widely adopted following trials on HMS Perseus between 1950 and 1952 which showed it to be more powerful and reliable than the compressed air catapults which had been introduced in the 1930s. As now only nuclear powered carriers have boilers as part of their motive power system, the majority of aircraft carriers are now equipped with steam generating plant solely to power the catapults.

Another British invention was the glide-slope indicator (also known as a "meatball"). This was a gyroscopically-controlled lamp on the port side of the deck which could be seen by the aviator who was about to land, indicating to him whether he was too high or too low in relation to the desired glidepath. It also took into account the effect of the waves on the flight deck. The device became a necessity as the landing speed of aircraft increased.

The US Navy prematurely attempted to become a strategic nuclear force with the project to build United States, termed CVA, with the "A" signifying "atomic". This ship would have carried twin-propeller bombers, each of which could carry an atomic bomb. The project was cancelled under pressure from the newly-created United States Air Force, and the letter "A" was re-cycled to mean "attack." But this only delayed the growth of carriers. Nuclear weapons would put to sea despite Air Force objections in 1955 aboard USS Forrestal, and by the end of the fifties the Navy had a series of nuclear-armed attack aircraft.

The US Navy took nuclear power afloat in other ways by building aircraft carriers powered by nuclear reactors. USS Enterprise was the first aircraft carrier to be powered in this way and subsequent supercarriers took advantage of this technology to increase their endurance. The only other nation to have followed the US lead is France with Charles de Gaulle.

The post-war years also saw the development of the helicopter with different capabilities to a fighter aircraft. Whereas fixed-wing aircraft are suited to air-to-air combat and air-to-surface attack, helicopters are used to transport equipment and personnel and can be used in an anti-submarine warfare role with dipped sonar and missiles.

In the late 1950s and early 1960s, the UK converted some of its old carriers into Commando Carriers, sea-going helicopter airfields like HMS Bulwark. To militate against the expensive connotations of the term "aircraft carrier", the new Invincible class carriers were originally designated "through deck cruisers" and were initially helicopter only craft to operate as escort carriers. The arrival of the Sea Harrier meant they could carry fixed wing aircraft despite their short flight deck.

Aircraft carriers today

Aircraft carriers are generally the largest ships operated by navies; a Nimitz-class carrier powered by two nuclear reactors and four steam turbines is 1092 ft (333 m) long and costs about $10 billion. The United States has the majority of aircraft carriers with a dozen in service, and its aircraft carriers are a cornerstone of American power projection capability.

Ten countries maintain aircraft carriers: United States, United Kingdom, France, India, Russia, Spain, Brazil, Italy and Thailand. In addition the People's Republic of China's People's Liberation Army Navy possesses the former Soviet aircraft carrier Varyag, but most naval analysts believe that they have no intention to operate it, but instead are using Varyag to learn about carrier operations for a future Chinese aircraft carrier. Canada, China, Japan, Pakistan, Australia and Chile also operate helicopter-carrying vessels.

Aircraft carriers are generally accompanied by a number of other ships, to provide protection for the relatively unwieldy carrier, to carry supplies, and to provide additional offensive capabilities. This is often termed a battle group or carrier group, sometimes a carrier battle group.

Modern carriers

More modern uses of aircraft carriers include the Falklands War, where the United Kingdom was able to win a conflict 8,000 miles (13,000 km) from home in large part due to the use of the full size carrier HMS Hermes and the smaller HMS Invincible. The Falklands showed the value of a VSTOL aircraft—the Hawker-Siddeley Harrier (the RN Sea Harrier and press-ganged RAF Harriers) in defending the fleet and assault force from shore based aircraft and for attacking the enemy. Helicopters from the carriers were used to deploy troops and pick up the wounded.

The US has also made use of carriers in the Persian Gulf, Afghanistan and to protect its interests in the Pacific. Most recently, the 2003 invasion of Iraq featured US aircraft carriers as the primary base of US air power. Even without the ability to place significant numbers of aircraft in Middle Eastern airbases, the United States was capable of carrying out significant air attacks from carrier-based squadrons.

In the early 21st century, worldwide aircraft carriers were capable of carrying about 1250 aircraft. US carriers accounted for over 1000 of these; the second leading country, the United Kingdom fielded over 50 aircraft. The United Kingdom and France are both undergoing a major expansion in carrier capability (with a common ship class), but the United States will still maintain a very large lead.

Future aircraft carriers

Several nations which currently possess aircraft carriers are in the process of planning new classes, to replace current ones.

French Marine Nationale

The French Navy has set in motion plans for a second aircraft carrier, to supplement Charles de Gaulle. The design is to be much larger, in the range of 50–60,000 tonnes, and will not be nuclear-powered like Charles de Gaulle. There are plans to adopt the current Royal Navy design for CATOBAR operations (the Thales/ BAE Systems design for the Royal Navy is for a STOVL carrier which is reconfigureable to CATOBAR operations).

Indian Navy

India started the construction of a 37,500 tonne, 252 metre-long aircraft carrier in April 2005. The new carrier will cost US$762 million and will operate MiG 29K 'Fulcrum' and Sea Harrier aircraft along with Russian- and Indian-made helicopters. The ship will be powered by four turbine engines and when completed will have a range of 7,500 nautical miles, carrying 160 officers, 1400 sailors, and 30 aircraft. The carrier is to be constructed by a state-run shipyard in southern India. In 2004, India also bought Admiral Gorshkov from Russia for US$1.5 billion; it is expected to join the Indian Navy in 2008 after a refit.

Italian Marina Militare

The construction of the conventional powered Marina Militare V/STOL aircraft carrier Cavour began in 2001. It is being built by Fincantieri of Italy. After much delay, Cavour is expected to enter service in 2008 to complement the Marina Militare aircraft carrier Giuseppe Garibaldi. A second aircraft carrier in the 25-30,000 ton range is much desired by the Italian Navy, to replace the already decommissioned carrier Vittorio Veneto, but for budgetary reasons all further development is on hold.

People's Republic of China

In June 2005, it was reported by boxun.com that China would build a US$362 million aircraft carrier with a displacement of 78,000 tons, to be built by the Jiangnan Shipyard in Shanghai. The report was denied by Chinese defense official Zhang Guangqin. Previous attempts to purchase an aircraft carrier from Russia and France did not succeed.

British Royal Navy

The Royal Navy is currently planning two new larger aircraft carriers (as yet only known as CVF) to replace the two Invincible class carriers currently in service. These two ships are expected to be named HMS Queen Elizabeth and HMS Prince of Wales. They will be able to operate about 50 aircraft and will have a displacement of around 60,000 tonnes. The two ships are due to enter service in 2012 and 2015 respectively. Their primary aircraft complement will be made up of F-35 Joint Strike Fighter, and their ship's company will number around 1000.

The two ships will be the largest warships ever built for the Royal Navy. Initially to be configured for STOVL operations, the carriers are to be adaptable to allow any type of future generation of aircraft to operate from them.

Russian Federation

Has one operational aircraft carrier, Admiral Kuznetsov.

The Russian Federation is currently developing a new aircraft carrier design. They are starting from scratch to make a modern model, with the newest available materials and electronics. Requirements would be for two aircraft carriers - one for the Russian Baltic Fleet and one for the Russian Pacific Fleet. Construction is set to begin by 2010, and finish in around 6 years.

Spanish Armada Española

The project for the 231 meter-long and 25,000-30,000 tons conventional powered Buque de Proyección Estratégica (Strategic projection vessel) for the Spanish navy was approved in 2003, and its construction started in August 2005, with the ship-building firm Navantia in charge of the project. The Buque de proyección estratégica is a vessel designed to operate both as amphibious assault vessel and as VSTOL aircraft carrier, depending on the mission assigned. The design was made keeping in mind the low-intensity conflicts in which the Spanish Armada is going to be involved in the future. When it is configured to operate as VSTOL aircraft carrier, the operating range will be about 25,000 tons, and it will operate a maximum of 20 Matador AV-8B+, F-35 or a mixed force of both aircraft. The ship is provided with a Sky-Jump and a tri-dimensional radar based combat system, and she will be the second operating aircraft carrier of the Spanish navy after Príncipe de Asturias.

US Navy

The current US Fleet of Nimitz-class carriers are to be followed into service (and in some cases replaced) by the CVN-21/CVNX Carrier. It is expected that the ships will be larger and will operate more aircraft than the 80 or so of Nimitz, and will also be designed for lower detectability by radar.

Aircraft carriers in fiction

See the article on aircraft carriers in fiction for more information.