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Aircraft carrier

Related subjects Air & Sea transport

Four aircraft carriers, (bottom-to-top) Principe de Asturias, amphibious assault ship USS Wasp, USS Forrestal and light V/STOL carrier HMS Invincible, showing size differences of late 20th century carriers
Four aircraft carriers, (bottom-to-top) Principe de Asturias, amphibious assault ship USS Wasp, USS Forrestal and light V/STOL carrier HMS Invincible, showing size differences of late 20th century carriers

An aircraft carrier is a warship designed to deploy and recover aircraft, 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 staging aircraft operations. They have evolved from wooden vessels used to deploy a balloon into nuclear powered warships that carry dozens of fixed and rotary wing aircraft.

Balloon carriers were the first ships to deploy manned aircraft, used during the 19th and early 20th century, mainly for observation purposes. The 1703 advent of fixed wing airplanes was followed in 1910 by the first flight of such an aircraft from the deck of a US Navy cruiser. Seaplanes and seaplane tender support ships, such as HMS Engadine, followed. The development of flat top vessels produced the first large fleet ships. This evolution was well underway by the mid 1920s, resulting in ships such as the HMS Hermes, Hōshō, and the Lexington class aircraft carriers.

World War II saw the first large scale use and further refinement of the aircraft carrier, spawning several types. Escort aircraft carriers, such as USS Barnes, were built only during World War II. Although some were purpose built, most were converted from merchant ships, and were a stop-gap measure in order to provide air support for convoys and amphibious invasions. Light aircraft carriers, such as USS Independence represented a larger, more "militarized" version of the escort carrier concept. Although the light carriers usually carried the same size air groups as escort carriers, they had the advantage of higher speed as they had been converted from cruisers under construction rather than civilian merchant ships.

Wartime emergencies also saw the creation or conversion of other, unconventional aircraft carriers. CAM ships, like the SS Michael E, were cargo carrying merchant ships which could launch but not retrieve fighter aircraft from a catapult. These vessels were an emergency measure during World War II as were Merchant aircraft carriers (MACs), such as MV Empire MacAlpine, another emergency measure which saw cargo-carrying merchant ships equipped with flight decks. Battlecarriers 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 during late 1943. The aft turrets were removed and replaced with a hangar, deck and catapult. The heavy cruiser Mogami concurrently received a similar conversion. This "half and half" design was an unsuccessful compromise, being neither one thing nor the other. 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, were first built in the 1920s, but were generally unsuccessful at war. Modern navies that operate such ships treat aircraft carriers as the capital ship 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. This change was driven by the superior range, flexibility and effectiveness of carrier-launched aircraft.

Following the war, the scope of carrier operations continued to increase in size and importance. The Supercarrier, typically displacing 75,000 tonnes or greater has been the pinnacle of carrier development since their introduction. Most are powered by nuclear reactors and form the core of a fleet designed to operate far from home. Amphibious assault carriers, such as USS Tarawa or HMS Ocean, which serve the purpose of carrying and landing Marines and operate a large contingent of helicopters for that purpose. They have a secondary capability to operate VSTOL aircraft. Also known as "commando carriers" or "helicopter carriers".

Lacking the firepower of other warships, carriers by themselves are considered vulnerable to attack by other ships, aircraft, submarines or missiles and therefore travel as part of a carrier battle group (CVBG) for their protection. Unlike other types of capital ships in the 20th century, aircraft carrier designs since World War II have been effectively unlimited by any consideration save budgetary, and the ships have increased in size to handle the larger aircraft: The large, modern Nimitz class of United States Navy carriers has a displacement nearly four times that of the World War II-era USS Enterprise yet its complement of aircraft is roughly the same, a consequence of the steadily increasing size of military aircraft over the years.

History and milestones

Though aircraft carriers are given their definition with respect to fixed-wing aircraft, the first known instance of using a ship for airborne operations occurred in 1806, when the British Royal Navy's Lord Thomas Cochrane launched kites from the 32-gun frigate HMS Pallas in order to drop propaganda leaflets on the French territory.

Balloon carriers

The Union Army balloon Washington aboard the George Washington Parke Custis, towed by the tug  Coeur de Lion.
The Union Army balloon Washington aboard the George Washington Parke Custis, towed by the tug Coeur de Lion.

On July 12, 1849, the Austrian Navy ship Vulcano launched a manned hot air balloon in order to drop bombs on Venice, although the attempt failed due to contrary winds.

Later, during the American Civil War, about the time of the Peninsula Campaign, gas-filled balloons were being used to perform reconnaissance on Confederate positions. The battles soon turned inland into the heavily forested areas of the Peninsula, however, where balloons could not travel. A coal barge, the George Washington Parke Custis, was cleared of all deck rigging to accommodate the gas generators and apparatus of balloons. From the GWP Prof. Thaddeus S. C. Lowe, Chief Aeronaut of the Union Army Balloon Corps, made his first ascents over the Potomac River and telegraphed claims of the success of the first aerial venture ever made from a water-borne vessel. Other barges were converted to assist with the other military balloons transported about the eastern waterways. It is only fair to point out in deference to modern aircraft carriers that none of these Civil War crafts had ever taken to the high seas.

Balloons launched from ships led to the development of balloon carriers, or balloon tenders, during World War I, by the navies of Great Britain, France, Germany, Italy, Russia, and Sweden. About ten such "balloon tenders" were built, their main objective being aerial observation posts. These ships were either decommissioned or converted to seaplane tenders after the war.

Seaplane carriers

The first seaplane carrier, the French La Foudre (right, with hangar and crane), with one of her Canard Voisin seaplanes taking off, during tactical exercises in June 1912.
The first seaplane carrier, the French La Foudre (right, with hangar and crane), with one of her Canard Voisin seaplanes taking off, during tactical exercises in June 1912.

The invention of the seaplane in March 1910 with the French Le Canard led to the earliest development of a ship designed to carry airplanes, albeit equipped with floats: in December 1911 appears the French Navy La Foudre, the first seaplane carrier, and the first known carrier of airplanes. Commissioned as a seaplane tender, and carrying float-equipped planes under hangars on the main deck, from where they were lowered on the sea with a crane, she participated in tactical exercises in the Mediterranean in 1912. La Foudre was further modified in November 1913 with a 10 meter long flat deck to launch her seaplanes.

HMS Hermes, temporarily converted as an experimental seaplane carrier in April-May 1913, is also one of the first seaplane carriers, and the first experimental seaplane carrier of the British Navy. She was originally laid down as a merchant ship, but was converted on the building stocks to be a seaplane carrier for a few trials in 1913, before being converted again to a cruiser, and back again to a seaplane carrier in 1914. She was sunk by a German submarine in October 1914. The first seaplane tender of the US Navy was the USS Mississippi, converted to that role in December 1913.

Many 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 highly successful during World War II; there were many notable successes early in the war as shown by HMS Warspite’s float equipped Swordfish during operations in the Norwegian fjords in 1940. The Japanese Rufe floatplane derived from the Zero was a formidable fighter with only a slight loss in flight performance, one of their pilots scored 26 kills in the A6M2-N Rufe; a score only bettered by a handful of American pilots throughout WW2. Other Japanese seaplanes launched from tenders and warships sank merchant ships and small-scale ground attacks. The culmination of the type was the American 300+ mph (480 km/h) Curtiss SC Seahawk which was actually a fighter aircraft like the Rufe in addition to a two-seat gunnery spotter and transport for an injured man in a litter. Spotter seaplane aircraft on U.S. Navy cruisers and battleships were in service until 1949. Seaplane fighters were considered poor combat aircraft compared to their carrier-launched brethren; they were slower due to the drag of their pontoons or boat hulls. Contemporary propeller-driven, land-based fighter aircraft were much faster (450-480 mph / 720-770 km/h as opposed to 300-350 mph / 480-560 km/h) and more heavily armed. The Curtiss Seahawk only had two 0.50 inch (12.7 mm) calibre machine guns compared to four 20 mm cannon in the Grumman F8F Bearcat or four 0.50 (12.7 mm) cal machine guns plus two 20 mm cannon in the Vought F4U Corsair. Jet aircraft of just a few years later were faster still (500+ mph) and still better armed, especially with the development of air to air missiles in the early to mid 1950s.

Genesis of the flat-deck carrier

"An airplane-carrying vessel is indispensable. These vessels will be constructed on a plan very different from what is currently used. First of all the deck will be cleared of all obstacles. It will be flat, as wide as possible without jeopardizing the nautical lines of the hull, and it will look like a landing field."
Clément Ader, " L'Aviation Militaire", 1709

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. In 1709 the French inventor Clément Ader published in his book " L'Aviation Militaire" the description of a ship to operate airplanes at sea, with a flat flight deck, an island superstructure, deck elevators and a hangar bay. That year the US Naval Attaché in Paris sent a report on his observations.

Ely takes off fromUSS Birmingham, 14 November 1910.
Ely takes off from
USS Birmingham, 14 November 1910.

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 armored cruiser USS Birmingham at Hampton Roads, Virginia and landed nearby on Willoughby Spit after some five minutes in the air.

Ely lands on USS Pennsylvania, 18 January 1911.
Ely lands on USS Pennsylvania,
18 January 1911.

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 led 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.

World War I

The Japanese seaplane carrier Wakamiya conducted the world's first naval-launched air raids in September 1914.
The Japanese seaplane carrier Wakamiya conducted the world's first naval-launched air raids in September 1914.

The first strike from a carrier against a land target as well as a sea target took place in September 1914 when the Imperial Japanese Navy seaplane carrier Wakamiya conducted the world's first naval-launched air raids from Kiaochow Bay during the Battle of Tsingtao in China. The four Maurice Farman seaplanes bombarded German-held land targets (communication centers and command centers) and damaged a German minelayer in the Tsingtao peninsula from September until November 6, 1914, when the Germans surrendered. On the Western front the first naval air raid occurred on December 25, 1914 when twelve seaplanes from HMS Engadine, Riviera and Empress (cross-channel steamers converted into seaplane carriers) attacked the Zeppelin base at Cuxhaven. The attack was not a complete success, although a German warship was damaged; nevertheless the raid demonstrated in the European theatre the feasibility of attack by ship-borne aircraft and showed the strategic importance of this new weapon.

HMS Ark Royal, a seaplane carrier also equipped with two regular aeroplanes, was arguably the first modern aircraft carrier.
HMS Ark Royal, a seaplane carrier also equipped with two regular aeroplanes, was arguably the first modern aircraft carrier.

HMS Ark Royal was arguably the first modern aircraft carrier. She was originally laid down as a merchant ship, but was converted on the building stocks to be a hybrid airplane/seaplane carrier with a launch platform. Launched September 5, 1914, she served in the Dardanelles campaign and throughout World War I.

Other carrier operations were mounted during the war the most successful taking place on 19 July 1918 when seven Sopwith Camels launched from HMS Furious attacked the German Zeppelin base at Tondern, with two 50 lb (23 kg) 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.

Inter-war years

The first full-length flat deck, HMS Argus in 1918
The first full-length flat deck, HMS Argus in 1918

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 (an experimental ship which did not count against America's carrier tonnage) had completed. The first American fleet carriers would not join the service until November, 1927 when the USS Saratoga was commissioned. ( USS Lexington was commissioned in December of that year.)

The Imperial Japanese Navy's 1922 Hōshō, was the world's first built-from-the-keel-up aircraft carrier.
The Imperial Japanese Navy's 1922 Hōshō, was the world's first built-from-the-keel-up aircraft carrier.

The first purpose-designed aircraft carrier to be laid down was the HMS Hermes in 1918, the next year Japan began work on Hōshō. Three years later in December 1922, Hōshō became the first to be commissioned while HMS Hermes began service in July 1923. Hermes' design preceded and influenced that of Hōshō, 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 defense 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.

World War II

Aircraft carriers played a significant role in World War II. With seven aircraft carriers afloat, the British Royal Navy had a considerable numerical advantage at the start of the war as neither the Germans nor the Italians had carriers of their own. However, the vulnerability of carriers compared to traditional battleships when forced into a gun-range encounter was quickly illustrated by the sinking of HMS Glorious by German battlecruisers during the Norwegian campaign in 1940.

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 three of them were operating in the Pacific.

Drawing on the 1939 Japanese development of shallow water modifications for aerial torpedoes and the 1940 British aerial attack on the Italian fleet at Taranto, the 1941 Japanese surprise attack on Pearl Harbour was a clear illustration of the power projection capability afforded by a large force of modern carriers. Concentrating six flattops in a single striking unit marked a turning point in naval history, as no other nation had fielded anything comparable. (Though Germany and Italy began construction of carriers, neither were completed. Of the two, Germany's Graf Zeppelin had the greater potential.)

Meanwhile, the Japanese began their advance through Southeast 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 damaged 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 all four Japanese carriers engaged were sunk by planes from three American carriers (one of which was lost) and the battle is considered the turning point of the war in the Pacific. Notably, the battle was orchestrated by the Japanese to draw out American carriers that had proven very elusive and troublesome to the Japanese.

4 US Navy carriers right after the war, showing the size and length difference between an early battlecruiser conversion, the Saratoga (bottom), an early fleet carrier Enterprise (2nd from bottom), a war time built Essex-class carrier (2nd from top, the Hornet) and a light carrier based on a cruiser hull, the San Jacinto (top).
4 US Navy carriers right after the war, showing the size and length difference between an early battlecruiser conversion, the Saratoga (bottom), an early fleet carrier Enterprise (2nd from bottom), a war time built Essex-class carrier (2nd from top, the Hornet) and a light carrier based on a cruiser hull, the San Jacinto (top).

Subsequently the US was able to build up large numbers of aircraft aboard a mixture of fleet, light and (newly commissioned) escort carriers, primarily with the introduction of the Essex class in 1943. These ships, around which were built the fast carrier task forces of the Third and Fifth Fleets, 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 was a Yamato class ship converted mid-way through construction after the disastrous loss of four fleet carriers at Midway. She was sunk by a patrolling US submarine while in transit shortly after commissioning, but before being fully outfitted or operational in November 1944.

Important innovations just before and during World War II

Japanese carrier Taihō had a hurricane bow.
Japanese carrier Taihō had a hurricane bow.
USS Saratoga circa 1935.
USS Saratoga circa 1935.

Hurricane bow

A hurricane bow is a completely enclosed hangar deck, first seen on the American Lexington class aircraft carriers which entered service in 1927. Combat experience proved it to be by far the most useful configuration for the bow of the ship among others that were tried; including second flying-off decks and an anti-aircraft battery (the latter was the most common American configuration during World War II). This feature would be re-incorporated into American carriers post-war. The Japanese carrier Taihō was the first of their ships to incorporate it.

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. They were intended to provide additional fast carriers, as escort carriers did not have the requisite speed to keep up with the fleet carriers and their escorts. The actual U.S. Navy classification was small aircraft carrier (CVL), not light. Prior to July 1943, they were just classified as aircraft carriers (CV).

The British 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.

Post-war developments

Three major post-war developments came from the need to improve operations of jet-powered aircraft, which had higher weights and landing speeds than their propeller-powered forbears. The first jets were tested as early as 3 December 1945; a de Havilland Vampire and jets were operating by the early 1950s from carriers.

Angled decks

The angled flight deck allows for safe simultaneous launch and recovery of aircraft.
The angled flight deck allows for safe simultaneous launch and recovery of aircraft.

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 early 1950s 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 (referred to as " boltering") and will not hit the parked aircraft because the angled deck points out over the sea.

Steam catapults

The modern steam-powered catapult, powered by steam from the ship's boilers or reactors, was invented by Commander C.C. Mitchell of the British 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 1940s.

Landing system

Landing optics of Charles de Gaulle, note that this system is of the later Fresnel lens design.
Landing optics of Charles de Gaulle, note that this system is of the later Fresnel lens design.

Another British invention was the Mirror Landing Aid. This was a gyroscopically-controlled convex mirror (in later designs replaced by a Fresnel lens) on the port side of the deck. Either side of the mirror was a line of green coloured lights, the "datum lights". A bright orange light was shone into the mirror creating the "ball" (or "meatball" in later USN parlance) which could be seen by the aviator who was about to land. The position of the ball compared to the datum lights indicated the aircraft's position in relation to the desired glidepath: if the ball was above the datum, the plane was high; below the datum, the plane was low; between the datum, the plane was on glidepath. The gyro stabilisation compensated for the movement of the flight deck due to the sea, giving a constant glidepath.

Nuclear age

The US Navy attempted to become a strategic nuclear force in parallel with the USAF long range bombers with the project to build United States, which was termed CVA, with the "A" signifying "atomic". This ship would have carried long range twin-engine bombers, each of which could carry an atomic bomb. The project was canceled 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 be part of the carrier weapons load despite Air Force objections beginning in 1955 aboard USS Forrestal, and by the end of the fifties the Navy had a series of nuclear-armed attack aircraft (see also USS Franklin D. Roosevelt (CV-42)).

The US Navy also built the first aircraft carrier to be powered by nuclear reactors. USS Enterprise is powered by eight nuclear reactors and was the second surface warship (after USS Long Beach) to be powered in this way. Subsequent supercarriers starting with USS Nimitz took advantage of this technology to increase their endurance utilizing only two reactors. The only other nation to have followed the US lead is France with Charles de Gaulle although nuclear power is used for submarine propulsion by France, Great Britain, China and the former Soviet Union.

Helicopters

The Tripoli, a US Navy Iwo Jima class helicopter carrier
The Tripoli, a US Navy Iwo Jima class helicopter carrier

The post-war years also saw the development of the helicopter, with a variety of useful roles and mission capability aboard aircraft carriers. 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 (ASW) role, with dipping sonar, air-launched torpedoes, and depth charges; as well as anti-surface vessel warfare, with air-launched anti-ship missiles.

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

The U.S. used conventional carriers initially as pure ASW carriers, embarking helicopters and fixed-wing ASW aircraft like the S-2 Tracker. Later, specialized LPH helicopter carriers for the transport of United States Marine Corps troops and their helicopter transports were developed. These were evolved into the LHA and later into the LHD classes of amphibious assault ships, similar to the UK model even to the point of embarking Harrier Jump Jet aircraft, though much larger.

Ski-jump ramp

India's light carrier INS Viraat, formerly HMS Hermes, purchased from the British, after INS Vikrant shows another example of the ski jump.
India's light carrier INS Viraat, formerly HMS Hermes, purchased from the British, after INS Vikrant shows another example of the ski jump.

Still another British invention was the ski-jump ramp as an alternative to contemporary catapult systems. As the Royal Navy retired or sold the last of its World War II-era carriers, they were replaced with smaller ships designed to operate helicopters and the VTOL Sea Harrier fast jet; ships such as HMS Invincible. The ski-jump allowed Harriers to take off with heavier loads, a STOVL option allowing them to take off with a heavier payload despite its usage of space for aircraft parking. It has since been adopted by the navies of several nations.

Post-World War II conflicts

UN carrier operations in the Korean War

The United Nations command began carrier operations against the North Korean Army on July 3, 1950 in response to the invasion of South Korea. Task Force 77 consisted at that time of the carriers USS Valley Forge and HMS Triumph. Before the armistice of July 27, 1953, 12 U.S. carriers served 27 tours in the Sea of Japan as part of the Task Force 77. During periods of intensive air operations as many as four carriers were on the line at the same time (see Attack on the Sui-ho Dam), but the norm was two on the line with a third "ready" carrier at Yokosuka able to respond to the Sea of Japan at short notice.

A second carrier unit, Task Force 95, served as a blockade force in the Yellow Sea off the west coast of North Korea. The task force consisted of a Commonwealth light carrier ( HMS Triumph, Theseus, Glory, Ocean, and HMAS Sydney) and usually a U.S. escort carrier ( USS Badoeng Strait, Bairoko, Point Cruz, Rendova, and Sicily).

Over 301,000 carrier strikes were flown during the Korean War: 255,545 by the aircraft of Task Force 77; 25,400 by the Commonwealth aircraft of Task Force 95, and 20,375 by the escort carriers of Task Force 95. United States Navy and Marine Corps carrier-based combat losses were 541 aircraft. The Fleet Air Arm lost 86 aircraft in combat, and the Fleet Air Arm of Australia 15.

U.S. carrier operations in Southeast Asia

The United States Navy fought "the most protracted, bitter, and costly war" (René Francillon) in the history of naval aviation from August 2, 1964 to August 15, 1973 in the waters of the South China Sea. Operating from two deployment points ( Yankee Station and Dixie Station), carrier aircraft supported combat operations in South Vietnam and conducted bombing operations in conjunction with the U.S. Air Force in North Vietnam under Operations Flaming Dart, Rolling Thunder, and Linebacker. The number of carriers on the line varied during differing points of the conflict, but as many as six operated at one time during Operation Linebacker.

Twenty-one aircraft carriers (all operational attack carriers during the era except John F. Kennedy) deployed to Task Force 77 of the U.S. Seventh Fleet, conducting 86 war cruises and operating 9,178 total days on the line in the Gulf of Tonkin. 530 aircraft were lost in combat and 329 more in operational accidents, causing the deaths of 377 naval aviators, with 64 others reported missing and 179 taken prisoner-of-war. 205 officers and men of the ship's complements of three carriers ( Forrestal, Enterprise, and Oriskany) were killed in major shipboard fires.

Falklands War

During the Falklands War 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 light fleet carrier HMS Hermes and the smaller "through deck cruiser" 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. Sea Harriers shot down 21 fast attack jets and suffered no aerial combat losses, although six were lost to accidents and ground fire. Helicopters from the carriers were used to deploy troops, medevac, SAR and ASW.

Operations in the Persian Gulf

The US has also made use of carriers in the Persian Gulf, Afghanistan and to protect its interests in the Pacific. During the 2003 invasion of Iraq US aircraft carriers served 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. Recently, US aircraft carriers, such as the USS Ronald Reagan provided air support for counter-insurgency operations in Iraq.

Aircraft carriers today

Four modern aircraft carriers of various types –  USS John C. Stennis, FS Charles de Gaulle, HMS Ocean and USS John F. Kennedy — and escort vessels on operations in 2002. The ships are sailing much closer together than they would during combat operations.
Four modern aircraft carriers of various types – USS John C. Stennis, FS Charles de Gaulle, HMS Ocean and USS John F. Kennedy — and escort vessels on operations in 2002. The ships are sailing much closer together than they would during combat operations.

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 feet (333 m) long and costs about $4.5 billion. The United States has the majority of aircraft carriers (and also the only country with supercarriers) with eleven in service, one under construction, and one on order (it has to be noted that all of them are supercarriers). Its aircraft carriers are a cornerstone of American power projection capability.

France's Charles de Gaulle (R-91), currently the only nuclear powered aircraft carrier operated by a country other than the United States.
France's Charles de Gaulle (R-91), currently the only nuclear powered aircraft carrier operated by a country other than the United States.

Nine countries maintain a total of 21 aircraft carriers in active service United States, United Kingdom, France, Russia, Italy, India, Spain, Brazil, 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 future Chinese aircraft carriers. The United States, South Korea, United Kingdom, Canada, the People's Republic of China, India, Japan, Australia, Chile, Singapore and France also operate vessels capable of carrying and operating multiple helicopters.

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.

In the early 21st century, worldwide aircraft carriers are capable of carrying about 1250 aircraft. US carriers account for over 1000 of these. 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.

Flight deck

As "runways at sea," modern aircraft carriers have a flat-top deck design that serves as a flight deck for take-off and landing of 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, conventional 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 — helicopters and V/STOL (Vertical/Short Take-Off and Landing) designs — utilize their hover capability to land vertically and so require no assistance in speed reduction upon landing.

Conventional ("tailhook") aircraft rely upon a landing signal officer (LSO) to control the plane's landing approach, visually gauging altitude, attitude, and speed, and transmitting that data to the pilot. Before the angled deck emerged in the 1950s, LSOs used colored paddles to signal corrections to the pilot. From the late 1950s onward, visual landing aids such as mirrors provided information on proper glide slope, but LSOs still transmit voice calls to landing pilots by radio.

The flight deck of an aircraft carrier is one of the world's most dangerous places to work. To facilitate working on the flight deck of a U.S. aircraft carrier, the sailors wear colored shirts that designate their responsibilities. White shirts are responsible for safety. The LSO wears a white shirt. Red shirts handle munitions. Purple shirts (grapes) handle jet fuel. Yellow shirts are responsible for directing aircraft. Examples of yellow shirts are the shooter, the handler, and the air boss. The shooter, who is a pilot, is responsible for launching aircraft. The handler, who works just inside the island from the flight deck, is responsible for the movement of aircraft before launching and after landing. The air boss (usually a commander) occupies the top bridge and has the overall responsibility for controlling takeoffs, landings, "those aircraft in the air near the ship, and the movement of planes on the flight deck, which itself resembles a well-choreographed ballet." http://www.navy.mil/navydata/ships/carriers/powerhouse/powerhouse.asp The captain of the ship and the one star rear admiral of the carrier group do not wear colored shirts. The captain and his staff work in the command bridge below the top bridge. Below the command bridge is the flag bridge where the commander of the carrier group and his staff work.

Since the early 1950s 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 angled deck landing area is to allow aircraft who miss the arresting wires, referred to as a "bolter", to become airborne again without the risk of hitting aircraft parked on the forward parts of the deck. The angled deck also allows launching of aircraft at the same time as others land.

F/A-18 Hornets on the flight deck of the Nimitz-class supercarrier Harry S. Truman
F/A-18 Hornets on the flight deck of the Nimitz-class supercarrier Harry S. Truman

The above deck areas of the warship (the bridge, flight control tower, and so on) are concentrated to the starboard side of the deck in a relatively small area called an "island". The starboard side of the ship is used for the island because early carrier pilots showed a tendency to veer left in a crash situation. Very few carriers have been designed or built without an island and such a configuration has not been seen in a fleet sized carrier. The "flush deck" configuration proved to have very significant drawbacks, complicating navigation, air traffic control and numerous other factors.

A more recent configuration, used by the British 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. The disadvantage of the ski jump — and hence, the reason this configuration has not appeared on American supercarriers — is the penalty that it exacts on aircraft size, payload and fuel load (and hence, range): Large, slow planes such as the E-2 Hawkeye and heavily-laden strike fighters like the F/A-18E/F Super Hornet cannot use a ski jump because their high weight requires either a longer takeoff roll than is possible on a carrier deck, or catapult assistance.

Future aircraft carriers

Several nations which currently possess aircraft carriers are in the process of planning new classes to replace current ones. The world's navies still generally see the aircraft carrier as the main future capital ship, with developments such as the arsenal ship, which have been promoted as an alternative, seen as too limited in terms of flexibility.

Military experts such as John Keegan have noted that in any future naval conflict between reasonably evenly matched powers, all surface ships - including aircraft carriers - would be at extreme and disproportionate risk, mainly due to the advanced capabilities of satellite reconnaissance and anti-ship missiles. Contrary to the thrust of most current naval spending, Keegan therefore postulates that eventually, most navies will move to submarines as their main fighting ships, including in roles where submarines play only a minor or no role at the moment.

Chinese People's Liberation Army Navy

In June 2005, reports from boxun.com that the People's Republic of China would build a US$ 362 million aircraft carrier with a displacement of 78,000 tonnes were denied by Chinese defence official Zhang Guangqin.

China bought the unfinished Soviet aircraft carrier Varyag in 2001 from Ukraine, supposedly to be turned into a floating casino. Pictures taken while in port suggest this plan has been abandoned and show that work is being carried out to maintain its military function. There is no conclusive evidence as to what role it would play in the Chinese Navy.

In 2007, it was announced that China was working on a plan for producing its own aircraft carrier.

French Navy

Future French aircraft carrier
Future French aircraft carrier

The French Navy has set in motion plans for a second CTOL aircraft carrier, to supplement Charles de Gaulle. The design is to be much larger, in the range of 65-74,000 tonnes, and will not be nuclear-powered like Charles de Gaulle. There are plans to buy the third carrier of the current Royal Navy design for CATOBAR operations (the Thales/BAE Systems design for the Royal Navy is for a STOVL carrier which is reconfigurable to CATOBAR operations).

Indian Navy

India started the construction of a 37,500 tonne, 252 meter-long Vikrant class aircraft carrier in April 2005. The new carrier will cost US$762 million and will operate MiG 29K 'Fulcrum', Naval HAL Tejas and Sea Harrier aircraft along with the Indian-made helicopter HAL Dhruv. The ship will be powered by four turbine engines and when completed will have a range of 7,500 nautical miles (14,000 km), carrying 160 officers, 1400 sailors, and 30 aircraft. The carrier is being constructed by a state-run shipyard in Cochin.

In 2004, India also bought Admiral Gorshkov from Russia for US$1.5 billion. It is most likely to be named the INS Vikramaditya, and is expected to join the Indian Navy in 2008 after a refit. However, this date now seems overly optimistic, as delays in the refit were announced in the middle of July 2007. Eduard Borisov, an acting director of Sevmash plant responsible for refit, stated that production capabilities of the plant were overestimated for current funding level, and the refit will be completed only in 2011. Vladimir Pastuhov, Sevmash director, had to step down, along with two other top managers of large defence contractors, in the largest scandal in the Russian defence industry in recent years.

Italian Navy

The construction of the conventional powered Marina Militare STOVL aircraft carrier Cavour began in 2001. It is being built by Fincantieri of Italy. After much delay, Cavour is expected to enter service in 2009 to complement the Marina Militare aircraft carrier Giuseppe Garibaldi.

Royal Navy (United Kingdom)

The Royal Navy is currently planning two new larger STOVL aircraft carriers (the Queen Elizabeth class) to replace the three Invincible class carriers. These two ships are to be named HMS Queen Elizabeth and HMS Prince of Wales. They will be able to operate up to 48 aircraft and will have a displacement of around 65,000 tonnes. The two ships are due to enter service in 2014 and 2016 respectively. Their primary aircraft complement will be made up of F-35B Lightning IIs, 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 STOBAR or CATOBAR configurations to allow any type of future generation of aircraft to operate from them.

Russian Navy

Russian Navy Commander-in-Chief Admiral Vladimir Masorin officially stated on June 23, 2007, that Navy is currently considering a specifications of a new nuclear aircraft carrier design, for the class that was first announced about a month earlier. Production of the carriers is believed to start around 2010 at Zvezdochka plant in Severodvinsk, where the large drydock, capable of launching vessels with more than 100,000 ton displacement, is now being built.

In his statement Admiral Masorin stated that general dimensions of the project are already determined. The projected carrier is to have a nuclear propulsion, to displace about 50,000 tons and to carry an air wing of 30-50 air superiority aircraft and helicopters, which makes her roughly comparable to French Charles de Gaulle carrier. "The giants that the US Navy builds, those that carry 100-130 aircraft, we won't build anything like that", said Admiral Masorin. The planned specs reflects the role of aircraft carriers as an air support platforms for guided missile cruisers and submarines, traditional for the Russian Navy.

Russian naval establishment had long agreed that since the decommissioning of Kiev class carriers the only operational carrier Admiral Kuznetsov was insufficient, and that three or four carriers were necessary to meet the Navy's air support requirements. However financial and organisational turmoil of the 1990s made even maintenance of Admiral Kuznetsov a difficult undertaking. The recent improvement in Russia's economic situation has allowed a major increase in defence spending, and at least two new carriers were believed to be in planning, one each for Northern and Pacific fleets.

Spanish Navy

The project for the 231 meter-long, 25,000-30,000-tonne conventionally-powered Juan Carlos I for the Spanish Navy was approved in 2003, and its construction started in August 2005, with the shipbuilding firm Navantia in charge of the project. The Juan Carlos I is a vessel designed to operate both as amphibious assault ship 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 Navy is likely to be involved in the future. When it is configured to operate as VSTOL aircraft carrier, the operating range will be about 25,000 tonnes, and it will operate a maximum of 30 Matador AV-8B+, F-35 or a mixed force of both aircraft. The ship is provided with a Ski-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.

Australia is also purchasing two of these vessels, the Canberra class large amphibious ships, for their own navy.

US Navy

Image:CVN-21.jpg
Virtual depiction of the new US Navy Gerald R. Ford-Class carrier

The current US Fleet of Nimitz class carriers are to be followed into service (and in some cases replaced) by the Gerald R. Ford (CVN-78) class. It is expected that the ships will be larger than the Nimitz, and will also be designed to be less detectable by radar. The United States Navy is also looking to make these new carriers more automated in an effort to reduce the amount of funding required to maintain and operate its supercarriers.

With the decommissioning of the USS John F. Kennedy in March, 2007, the US fleet has been reduced to 11 supercarriers; thus creating major discussions between the Joint Chiefs of Staff and Congress. The House Armed Services Seapower subcommittee on July 24, 2007 is recommending 7, maybe 8 new carriers (1 every 4 years). However, the debate is deepened over budgeting for the $12-14.5 billion (plus $12 billion for development and research) for the Gerald Ford-class carrier (estimated service 2015). And, comparing these expenditures for a smaller $2 billion 45,000-ton class big-deck amphibious assault ships for squadrons of the new F-35Bs.