Aircraft carrier

Four modern aircraft carriers of various types—USS John C. Stennis, Charles de Gaulle, USS John F. Kennedy, helicopter carrier HMS Ocean—and escort vessels, 2002

From bottom to top: Spanish light V/STOL carrier Príncipe de Asturias, amphibious assault ship USS Wasp, fleet carrier USS Forrestal, and light V/STOL carrier HMS Invincible, showing size differences of late 20th century carriers, 1991

An aircraft carrier is a warship that serves as a seagoing airbase, equipped with a full-length flight deck and facilities for carrying, arming, deploying, and recovering aircraft.^[1] Typically, it is the capital ship of a fleet, as it allows a naval force to project air power worldwide without depending on local bases for staging aircraft operations. Aircraft carriers are expensive to build and are critical assets. Carriers have evolved since their inception in the early twentieth century from wooden vessels used to deploy balloons to nuclear-powered warships that carry numerous fighter planes, strike aircraft, helicopters, and other types of aircraft.

There is no single definition of an "aircraft carrier,"^[2] and modern navies use several variants of the type. These variants are sometimes categorized as sub-types of aircraft carriers,^[3] and sometimes as distinct types of naval aviation-capable ships.^[2]^[4] Aircraft carriers may be classified according to the type of aircraft they carry and their operational assignments. Admiral Sir Mark Stanhope, former head of the Royal Navy, has said, "To put it simply, countries that aspire to strategic international influence have aircraft carriers".^[5]

As of April 2024, there are 37 active aircraft carriers in the world within twelve navies. The United States Navy has 10 large nuclear-powered fleet carriers (known as supercarriers, carrying up to around 80 fighter jets each), the largest carriers in the world; the total combined deckspace is over twice that of all other nations combined.^[6] As well as the supercarrier fleet, the US Navy has nine amphibious assault ships used primarily for helicopters (sometimes called helicopter carriers), though these can also carry up to 20 vertical or short take-off and landing (V/STOL) fighter jets and are similar in size to light fleet carriers. China, France, India and Russia each operate a medium-size carrier, with capacity from 30 to 50 fighter jets, while several light fleet carriers, amphibious assault ships, and helicopter carriers, are also operated by various navies. Britain is building two 280 m (920 ft) carriers, the Queen Elizabeth and the Prince of Wales, scheduled to enter service in the Royal Navy in between 2020 and 2023.

Types of carrier

Brazilian aircraft carrier NAe São Paulo, foreground, and U.S. Navy carrier USS Ronald Reagan during a combined training exercise.

USS Enterprise, a supercarrier of the US Navy (left), sails alongside Charles de Gaulle, a fleet carrier of the French Navy (right), both of which have the CATOBAR configuration.

Cavour, a light aircraft carrier of the Italian Navy.

HMS Ocean of the Royal Navy, an amphibious assault ship/helicopter carrier.

Basic types

(note: some of the types listed here are not strictly defined as aircraft carriers by some sources)

By role

A fleet carrier is intended to operate with the main fleet and usually provides an offensive capability. These are the largest carriers capable of fast speeds. By comparison, escort carriers were developed to provide defense for convoys of ships. They were smaller and slower with lower numbers of aircraft carried. Most were built from mercantile hulls or, in the case of merchant aircraft carriers, were bulk cargo ships with a flight deck added on top. Light aircraft carriers were fast enough to operate with the main fleet but of smaller size with reduced aircraft capacity. Soviet aircraft carriers now in use by Russia are actually called heavy aviation cruisers; these ships, while sized in the range of large fleet carriers, were designed to deploy alone or with escorts, and provide both strong defensive weaponry and heavy offensive missiles equivalent to a guided missile cruiser, in addition to supporting fighters and helicopters.

By configuration

INS Vikramaditya of the Indian Navy has the STOBAR configuration.

There are four main configurations of aircraft carrier in service in the world's navies, divided by the way that aircraft take off and land:

Catapult-assisted take-off but arrested-recovery (CATOBAR): these carriers generally carry the largest, heaviest, and most heavily armed aircraft, although smaller CATOBAR carriers may have other limitations (weight capacity of aircraft elevator, etc.). Three nations currently operate carriers of this type: ten by the United States, and one each by France and Brazil for a total of twelve in service.
Short take-off but arrested-recovery (STOBAR): these carriers are generally limited to carrying lighter fixed-wing aircraft with more limited payloads. STOBAR carrier air wings, such as the Sukhoi Su-33 and future Mikoyan MiG-29K wings of Admiral Kuznetsov are often geared primarily towards air superiority and fleet defense roles rather than strike/power projection tasks,^{[citation needed]} which require heavier payloads (bombs and air-to-ground missiles). Currently, Russia, China, and India possess commissioned carriers of this type.
Short take-off vertical-landing (STOVL): limited to carrying STOVL aircraft. STOVL aircraft, such as the Harrier Jump Jet family and Yakovlev Yak-38 generally have limited payloads, lower performance, and high fuel consumption when compared with conventional fixed-wing aircraft; however, a new generation of STOVL aircraft, currently consisting of the F-35B, has much improved performance. This type of aircraft carrier is currently in service with Italy. Spain also operates one amphibious assault ship as a STOVL aircraft carrier for three ships total in active carrier service; Thailand has one active STOVL carrier but it no longer has any operational STOVL aircraft in inventory. Some also count the nine US amphibious assault ships in their secondary light carrier role boosting the overall total to thirteen. The UK is building two 70,000 ton STOVL carriers, HMS Queen Elizabeth and HMS Prince of Wales, the largest warships ever built for the Royal Navy; the first is expected to be "initial maritime operational capability" by 2020.
Helicopter carrier: Helicopter carriers have a similar appearance to other aircraft carriers and may support regular fixed wing operations. Some are designed for addition of, or may include, a ski jump ramp allowing for STOVL operations or may have an unused ski jump installed before retirement of STOVL aircraft and re-purposing. In the past, some conventional carriers were converted and called commando carriers by the Royal Navy. Some helicopter carriers with a resistant flight surface can operate STOVL jets. Currently the majority of helicopter carriers, but not all, are classified as amphibious assault ships, tasked with landing and supporting ground forces on enemy territory. The US has nine of this type, France and Japan three, Australia two, the UK one, the Republic of Korea (South Korea) one and Spain one. The US and Spain's amphibious assault ships operate STOVL jets in normal deployment.

By size

Hull type identification symbols

Several systems of identification symbol for aircraft carriers and related types of ship have been used. These include the pennant numbers used by the British Royal Navy and some Commonwealth countries, the US hull classification symbols also used by NATO and some other countries,^[7] and the Canadian hull classification symbols.

US hull classification symbols for aircraft carriers and related types
Symbol	Designation
CV	Generic aircraft carrier
CVA	Attack carrier
CVAN	Nuclear-powered attack carrier
CVE	Escort carrier
CVG	Flight deck cruiser (proposed)
CVHA	Aircraft carrier, Helicopter Assault (retired)
CVHE	Aircraft carrier, Helicopter, Escort (retired)
CVL	Light aircraft carrier
CVN	Nuclear-powered aircraft carrier
CVS	Anti-submarine warfare carrier
CVV	Aircraft Carrier, Medium (proposed)
LHA	Landing Helicopter Assault, a type of Amphibious assault ship
LHD	Landing Helicopter Dock, a type of Amphibious assault ship
LPH	Landing Platform Helicopter, a type of Amphibious assault ship

History

Origins

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

The 1903 advent of heavier-than-air fixed-wing aircraft was closely followed on 14 November 1910, by Eugene Burton Ely's first experimental take-off of a Curtiss pusher airplane from the deck of a United States Navy ship, the cruiser USS Birmingham anchored off Norfolk Navy Base in Virginia. Two months later, on 18 January 1911, Ely landed his Curtiss pusher airplane on a platform on the armored cruiser USS Pennsylvania anchored in San Francisco Bay. On 9 May 1912, the first airplane take-off from a ship underway was made from the deck of the British Royal Navy's HMS Hibernia.^[8]^[9] Seaplane tender support ships came next, with the French Foudre of 1911. Early in World War I, the Imperial Japanese Navy ship Wakamiya conducted the world's first successful ship-launched air raid:^[10]^[11] on 6 September 1914, a Farman aircraft launched by Wakamiya attacked the Austro-Hungarian cruiser SMS Kaiserin Elisabeth and the German gunboat Jaguar in Kiaochow Bay off Tsingtao; neither was hit.^[12]^[13] The first carrier-launched airstrike was the Tondern Raid in July 1918. Seven Sopwith Camels launched from the converted battlecruiser HMS Furious (47) damaged the German airbase at Tønder and destroyed two zeppelin airships.^[14]

Aerial view of Hōshō of the Imperial Japanese Navy as completed in December 1922.

The development of flattop vessels produced the first large fleet ships. In 1918, HMS Argus became the world's first carrier capable of launching and recovering naval aircraft.^[15] As a result of the Washington Naval Treaty of 1922, which limited the construction of new heavy surface combat ships, most early aircraft carriers were conversions of ships that were laid down (or had served) as different ship types: cargo ships, cruisers, battlecruisers, or battleships. These conversions gave rise to the US Lexington-class aircraft carriers (1927), Japanese Akagi, and British Courageous class. Specialist carrier evolution was well underway, with several navies ordering and building warships that were purposefully designed to function as aircraft carriers by the mid-1920s, resulting in the commissioning of ships such as IJN Hōshō (1922), HMS Hermes (1924), and Béarn (1927). During World War II, these ships would become known as fleet carriers.^{[citation needed]}

World War II

Attack on carrier USS Franklin, 19 March 1945. The casualties included 724 killed.

USS Enterprise, the most decorated US ship of World War II.

The aircraft carrier dramatically changed naval combat in World War II, because air power was becoming a significant factor in warfare. The advent of aircraft as focal weapons was driven by the superior range, flexibility, and effectiveness of carrier-launched aircraft. They had greater range and precision than naval guns, making them highly effective. The versatility of the carrier was demonstrated in November 1940, when HMS Illustrious launched a long-range strike on the Italian fleet at their base in Taranto, signalling the beginning of the effective and highly mobile aircraft strikes. This operation incapacitated three of the six battleships at a cost of two torpedo bombers. World War II in the Pacific Ocean involved clashes between aircraft carrier fleets. The 7 December 1941 Japanese surprise attack on Pearl Harbor was a clear illustration of the power projection capability afforded by a large force of modern carriers. Concentrating six carriers in a single unit turned naval history about, as no other nation had fielded anything comparable. 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 battleships during the Norwegian campaign in 1940.

This new-found importance of naval aviation forced nations to create a number of carriers, in efforts to provide air superiority cover for every major fleet in order to ward off enemy aircraft. This extensive usage led to the development and construction of 'light' carriers. Escort aircraft carriers, such as USS Bogue, were sometimes purpose-built but most were converted from merchant ships as a stop-gap measure to provide anti-submarine air support for convoys and amphibious invasions. Following this concept, light aircraft carriers built by the US, such as USS Independence, represented a larger, more "militarized" version of the escort carrier. Although with similar complement to escort carriers, they had the advantage of speed from their converted cruiser hulls. The UK 1942 Design Light Fleet Carrier was designed for building quickly by civilian shipyards and with an expected service life of about 3 years.^[16] They served the Royal Navy during the war and was the hull design chosen for nearly all aircraft carrier equipped navies after the war until the 1980s. Emergencies also spurred the creation or conversion of highly unconventional aircraft carriers. CAM ships, were cargo-carrying merchant ships that could launch (but not retrieve) a single fighter aircraft from a catapult to defend the convoy from long range German aircraft.

Postwar era

USS Tripoli, a US Navy Iwo Jima-class helicopter carrier

USS Enterprise (CVN-65), the world's first nuclear-powered carrier commissioned in 1961.

Before World War II, international naval treaties of 1922, 1930, and 1936 limited the size of capital ships including carriers. Since World War II, aircraft carrier designs have increased in size to accommodate a steady increase in aircraft size. The large, modern Nimitz class of US 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 and weight of military aircraft over the years. Today's aircraft carriers are so expensive that nations which operate them risk significant political, economic, and military impact if a carrier is lost, or even used in conflict.

Modern navies that operate such aircraft carriers treat them as the capital ship of the fleet, a role previously held by the battleship. This change took place during World War II in response to air power becoming a significant factor in warfare, driven by the superior range, flexibility and effectiveness of carrier-launched aircraft. Following the war, carrier operations continued to increase in size and importance. Supercarriers, displacing 75,000 tonnes or greater, have become the pinnacle of carrier development. Some are powered by nuclear reactors and form the core of a fleet designed to operate far from home. Amphibious assault ships, such as USS Tarawa and HMS Ocean, serve the purpose of carrying and landing Marines, and operate a large contingent of helicopters for that purpose. Also known as "commando carriers"^[17] or "helicopter carriers", many have the capability to operate VSTOL aircraft.

Lacking the firepower of other warships, carriers by themselves are considered vulnerable to attack by other ships, aircraft, submarines, or missiles. Therefore, an aircraft carrier is generally accompanied by a number of other ships to provide protection for the relatively unwieldy carrier, to carry supplies and perform other support services, and to provide additional offensive capabilities. The resulting group of ships is often termed a battle group, carrier group, or carrier battle group.

There is a view that modern anti-ship weapons systems, such as torpedoes and missiles, have made aircraft carriers obsolete as too vulnerable for modern combat.^[18] On the other hand, the threatening role of aircraft carriers has a place in modern asymmetric warfare, like the gunboat diplomacy of the past.^[19] Furthermore, aircraft carriers facilitate quick and precise projections of overwhelming military power into such local and regional conflicts.^[20]

Aircraft carriers in service

US Navy personnel direct an aircraft onto a catapult aboard the Nimitz-class aircraft carrier USS John C. Stennis.

Most navies operate only one or two aircraft carriers, if any. The USA is a notable exception, with 10 super carriers and 9 amphibious assault ships in service.

A total of 20 fleet carriers are in active service with ten navies. Additionally, the navies of Australia, Brazil, China, France, India, Italy, Japan, Russia, South Korea, Spain, Thailand and the United States also operate ships capable of carrying and operating multiple helicopters and STOVL aircraft.

CATOBAR types are operated by Brazil, France and especially the USA, which has ten in service.
STOBAR type are operated by China, India and Russia.
STOVL types are operated by India, Italy, Spain and the USA.

Among helicopter-only types:

ASW ships are operated by Japan.
An offshore helicopter support ship is operated by Thailand.
Amphibious assault ships are operated by Australia, France, the Republic of Korea, the United Kingdom and especially the USA, which has nine in service.

Future of aircraft carriers

Many aircraft carriers and related types are planned, under construction, or undergoing commissioning activity.

Australia

The Royal Australian Navy is in the process of procuring two Canberra-class LHDs, the first of which was commissioned in November 2015, while the second is expected to enter service in 2016.^[21] The ships will be the largest in Australian naval history. Their primary roles are to embark, transport and deploy an embarked force and to carry out or support humanitarian assistance missions. The LHD is capable of launching multiple helicopters at one time while maintaining an amphibious capability of 1,000 troops and their supporting vehicles (tanks, armoured personnel carriers etc.).^[22] The Australian Defence Minister has publicly raised the possibility of procuring F-35B STOVL aircraft for the carrier, stating that it "has been on the table since day one" and stating the LHDs are "STOVL capable".^[23]

India

INS Vikrant, an indigenously built aircraft carrier (IAC) was undocked on 10 June 2015.

JS Izumo just after her launch.

In December 2009, then Indian Navy chief Admiral Nirmal Kumar Verma said at his maiden Navy Week press conference that concepts currently being examined by the Directorate of Naval Design for the second indigenous aircraft carrier (IAC-II), are for a conventionally powered carrier displacing over 50,000 tons and equipped with steam catapults (rather than the ski-jump on the Gorshkov/Vikramaditya and the IAC-1) to launch fourth-generation aircraft.^[24] In August 2013, Vice Admiral RK Dhowan, while talking about the detailed study underway on the IAC-II project, said that nuclear propulsion was also being considered.^[25] The Indian Navy also evaluated the Electromagnetic Aircraft Launch System (EMALS), which is being used by the US Navy in their latest Gerald R. Ford-class aircraft carriers. General Atomics, the developer of the EMALS, was cleared by the US government to give a technical demonstration to Indian Navy officers, who were impressed by the new capabilities of the system. The EMALS enables launching varied aircraft including unmanned combat air vehicles (UCAV).^[26]^[27] The Indian Navy's goal is to have a total of three aircraft carriers in service, with two fully operational carriers and the third in refit.^[28]

Japan

In August 2013, a launching ceremony for Japan's largest military ship since World War II was held in Yokohama. The 820-foot-long (250 m), 19,500-ton flattop Izumo was deployed in March 2015.^[29] The ship is able to carry up to 14 helicopters; however, only seven ASW helicopters and two SAR helicopters were planned for the initial aircraft complement. For other operations, up to 400 troops and fifty 3.5 ton trucks (or equivalent equipment) can also be carried. The flight deck has five helicopter landing spots that allow simultaneous landings or take-offs. The ship is equipped with two Phalanx CIWS and two SeaRAM for its defense.

Russia

Speaking in St. Petersburg, Russia, on 30 June 2011, the head of Russia's United Shipbuilding Corporation said his company expected to begin design work for a new carrier in 2016, with a goal of beginning construction in 2018 and having the carrier achieve initial operational capability by 2023.^[30] Several months later, on 3 November 2011, the Russian newspaper Izvestiya reported that the naval building plan now included the construction of a new shipyard capable of building large hull ships, after which Moscow will build two (80,000 tons full load each) nuclear-powered aircraft carriers by 2027. The spokesperson said one carrier would be assigned to the Russian Navy's Northern Fleet at Murmansk, and the second would be stationed with the Pacific Fleet at Vladivostok.^[31]

South Korea

The Republic of Korea Navy (South Korea) believes it can deploy two light aircraft carriers by 2036 and expand its blue-water force to cope with the rapid naval buildups of China and Japan, according to a Navy source.^[32]

United Kingdom

File:HMS Queen Elizabeth.jpg

HMS Queen Elizabeth, the lead Queen Elizabeth-class supercarrier.

The British Royal Navy is constructing two new larger STOVL aircraft carriers, the Queen Elizabeth class, to replace the three Invincible-class carriers. The HMS Queen Elizabeth and HMS Prince of Wales^[33]^[34] will be able to operate up to 40 aircraft in peacetime, with a tailored group of up to 50, and will have a displacement of 70,600 tonnes. The ships are due to become operational from 2020.^[35] Their primary aircraft complement will be made up of F-35B Lightning IIs, and their ship's company will number around 680, with the total complement rising to about 1,600 when the air group is embarked. Defensive weapons will include the Phalanx CIWS for anti-aircraft and anti-missile defence, 30 mm Automated Small Calibre Guns, and miniguns for use against fast attack craft.^[36] The two ships will be the largest warships ever built for the Royal Navy.

United States

The current US fleet of Nimitz-class carriers will be followed into service (and in some cases replaced) by the ten-ship Gerald R. Ford class. The Ford-class ships will be more automated in an effort to reduce the amount of funding required to staff, maintain, and operate its supercarriers. The main new features are implementation of Electromagnetic Aircraft Launch System (EMALS) (which replace the old steam catapults) and unmanned aerial vehicles.^[37] With the deactivation of USS Enterprise in December 2012 (decommissioning scheduled for 2016), the US fleet comprises 10 active supercarriers. On 24 July 2007, the House Armed Services Seapower subcommittee recommended seven or eight new carriers (one every four years). However, the debate has deepened over budgeting for the $12–14.5 billion (plus $12 billion for development and research) for the 100,000 ton Gerald R. Ford-class carrier (estimated service 2016) compared to the smaller $2 billion 45,000 ton America-class amphibious assault ships able to deploy squadrons of F-35B of which one is already active, another is under construction, and nine more are planned.^[38]

Description

Structure

STOVL Harriers preparing to takeoff from CATOBAR carrier, USS Franklin D. Roosevelt

Carriers are large and long ships, although there is a high degree of variation depending on their intended role and aircraft complement. The size of the carrier has varied over history and among navies, to cater to the various roles that global climates have demanded from naval aviation.

Regardless of size, the ship itself must house their complement of aircraft, with space for launching, storing, and maintaining them. Space is also required for the large crew, supplies (food, munitions, fuel, engineering parts), and propulsion. US supercarriers are notable for having nuclear reactors powering their systems and propulsion. This makes the carrier reasonably tall.

The top of the carrier is the flight deck, where aircraft are launched and recovered. On the starboard side of this is the island, where air-traffic control and the bridge are located.

The constraints of constructing a flight deck affect the role of a given carrier strongly, as they influence the weight, type, and configuration of the aircraft that may be launched. For example, assisted launch mechanisms are used primarily for heavy aircraft, especially those loaded with air-to-ground weapons. CATOBAR is most commonly used on USN supercarriers as it allows the deployment of heavy jets with full loadouts, especially on ground-attack missions. STOVL is used by other navies because it is cheaper to operate and still provides good deployment capability for fighter aircraft.

The first carrier landing and take-off of a jet aircraft: Eric "Winkle" Brown landing on HMS Ocean in 1945.

Due to the busy nature of the flight deck, only 20 or so aircraft may be on it at any one time. A hangar storage several decks below the flight deck is where most aircraft are kept, and aircraft are taken from the lower storage decks to the flight deck through the use of an elevator. The hangar is usually quite large and can take up several decks of vertical space.^[39]

Munitions are commonly stored on the lower decks because they are highly explosive should the compartment they are in be breached. Usually this is below the water line so that the area can be flooded in case of emergency.

Flight deck

Catapult launches aboard USS Ronald Reagan.

Expansive Flight Deck of INS Vikramaditya at night showing the ski-jump ramp used for STOBAR configuration

As "runways at sea", aircraft carriers have a flat-top flight deck, which launches and recovers aircraft. Aircraft launch forward, into the wind, and are recovered from astern. The flight deck is where the most notable differences between a carrier and a land runway are found. Creating such a surface at sea poses constraints on the carrier – for example, the fact that it is a ship means that a full-length runway would be costly to construct and maintain. This affects take-off procedure, as a shorter runway length of the deck requires that aircraft accelerate more quickly to gain lift. This either requires a thrust boost, a vertical component to its velocity, or a reduced take-off load (to lower mass). The differing types of deck configuration, as above, influence the structure of the flight deck. The form of launch assistance a carrier provides is strongly related to the types of aircraft embarked and the design of the carrier itself.

There are two main philosophies in order to keep the deck short: add thrust to the aircraft, such as using a Catapult Assisted Take-Off (CATO-); and changing the direction of the airplanes' thrust, as in Vertical and/or Short Take-Off (V/STO-). Each method has advantages and disadvantages of its own:

Catapult assisted take-off but arrested recovery (CATOBAR): A steam-powered catapult is connected to the aircraft, and is used to accelerate conventional aircraft to a safe flying speed. By the end of the catapult stroke, the aircraft is airborne and further propulsion is provided by its own engines. This is the most expensive method as it requires complex machinery to be installed under the flight deck, but allows for even heavily loaded aircraft to take off.
Short take-off but arrested recovery (STOBAR) depends on increasing the net lift on the aircraft. Aircraft do not require catapult assistance for take off; instead on nearly all ships of this type an upwards vector is provided by a ski-jump at the forward end of the flight deck, often combined with thrust vectoring by the aircraft. Alternatively, by reducing the fuel and weapon load, an aircraft is able to reach faster speeds and generate more upwards lift and launch without a ski-jump or catapult.
Short take-off vertical-landing (STOVL): On aircraft carriers, non-catapult-assisted, fixed-wing short takeoffs are accomplished with the use of thrust vectoring, which may also be used in conjunction with a runway "ski-jump". Use of STOVL tends to allow aircraft to carry a larger payload as compared to during VTOL use, while still only requiring a short runway. The most famous examples are the Hawker Siddeley Harrier and the Sea Harrier. Although technically VTOL aircraft, they are operationally STOVL aircraft due to the extra weight carried at take-off for fuel and armaments. The same is true of the F-35B Lightning II, which demonstrated VTOL capability in test flights but is operationally STOVL.
Vertical take-off and landing (VTOL): Aircraft are specifically designed for the purpose of using very high degrees of thrust vectoring (e.g. if the thrust to weight-force ratio is greater than 1, it can take off vertically), but are usually slower than conventionally propelled aircraft.

On the recovery side of the flight deck, the adaptation to the aircraft loadout is mirrored. Non-VTOL or conventional aircraft cannot decelerate on their own, and almost all carriers using them must have arrested-recovery systems (-BAR, e.g. CATOBAR or STOBAR) to recover their aircraft. Aircraft that are landing extend a tailhook that catches on arrestor wires stretched across the deck to bring themselves to a stop in a short distance. Post-WWII Royal Navy research on safer CATOBAR recovery eventually led to universal adoption of a landing area angled off axis to allow aircraft who missed the arresting wires to "bolt" and safely return to flight for another landing attempt rather than crashing into aircraft on the forward deck.

If the aircraft are VTOL-capable or helicopters, they do not need to decelerate and hence there is no such need. The arrested-recovery system has used an angled deck since the 1950s because, in case the aircraft does not catch the arresting wire, the short deck allows easier take off by reducing the number of objects between the aircraft and the end of the runway. It also has the advantage of separating the recovery operation area from the launch area. Helicopters and aircraft capable of vertical or short take-off and landing (V/STOL) usually recover by coming abreast the carrier on the port side and then using their hover capability to move over the flight deck and land vertically without the need for arresting gear.

Staff and Deck Operations

F/A-18 landing video

Carriers steam at speed, up to 35 knots (65 km/h; 40 mph) into the wind during flight deck operations to increase wind speed over the deck to a safe minimum. This increase in effective wind speed provides a higher launch airspeed for aircraft at the end of the catapult stroke or ski-jump, as well as making recovery safer by reducing the difference between the relative speeds of the aircraft and ship.

Since the early 1950s on conventional carriers it has been the practice to recover aircraft at an angle to port of the axial line of the ship. The primary function of this angled deck is to allow aircraft that miss the arresting wires, referred to as a bolter, to become airborne again without the risk of hitting aircraft parked forward. The angled deck allows the installation of one or two "waist" catapults in addition to the two bow cats. An angled deck also improves launch and recovery cycle flexibility with the option of simultaneous launching and recovery of aircraft.

Conventional ("tailhook") aircraft rely upon a landing signal officer (LSO, radio call sign paddles) to monitor the aircraft's approach, visually gauge glideslope, attitude, and airspeed, and transmit that data to the pilot. Before the angled deck emerged in the 1950s, LSOs used colored paddles to signal corrections to the pilot (hence the nickname). From the late 1950s onward, visual landing aids such as Optical Landing System have provided information on proper glide slope, but LSOs still transmit voice calls to approaching pilots by radio.

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

Key personnel involved in the flight deck include the shooters, the handler, and the air boss. Shooters are naval aviators or Naval Flight Officers and are responsible for launching aircraft. The handler works just inside the island from the flight deck and is responsible for the movement of aircraft before launching and after recovery. The "air boss" (usually a commander) occupies the top bridge (Primary Flight Control, also called primary or the tower) and has the overall responsibility for controlling launch, recovery and "those aircraft in the air near the ship, and the movement of planes on the flight deck, which itself resembles a well-choreographed ballet."^[40] The captain of the ship spends most of his time one level below primary on the Navigation Bridge. Below this is the Flag Bridge, designated for the embarked admiral and his staff.

To facilitate working on the flight deck of a U.S. aircraft carrier, the sailors wear colored shirts that designate their responsibilities. There are at least seven different colors worn by flight deck personnel for modern United States Navy carrier air operations. Carrier operations of other nations use similar color schemes.

Deck structures

Island control structure of USS Enterprise

The superstructure of a carrier (such as the bridge, flight control tower) are concentrated in a relatively small area called an island, a feature pioneered on the HMS Hermes in 1923. While the island is usually built on the starboard side of the fight deck, the Japanese aircraft carriers Akagi and Hiryū had their islands built on the port side. Very few carriers have been designed or built without an island. The flush deck configuration proved to have significant drawbacks, primary of which was management of the exhaust from the power plant. Fumes coming across the deck were a major issue in USS Langley. In addition, lack of an island meant difficulties managing the flight deck, performing air traffic control, a lack of radar housing placements and problems with navigating and controlling the ship itself.^[41]

Another deck structure that can be seen is a ski-jump ramp at the forward end of the flight deck. This was first developed to help launch STOVL aircraft take off at far higher weights than is possible with a vertical or rolling takeoff on flat decks. Originally developed by the Royal Navy, it since has been adopted by many navies for smaller carriers. A ski-jump ramp works by converting some of the forward rolling movement of the aircraft into vertical velocity and is sometimes combined with the aiming of jet thrust partly downwards. This allows heavily loaded and fueled aircraft a few more precious seconds to attain sufficient air velocity and lift to sustain normal flight. Without a ski-jump launching fully loaded and fueled aircraft such as the Harrier would not be possible on a smaller flat deck ship before either stalling out or crashing directly into the sea.

Ski-jump on Royal Navy carrier HMS Invincible

Although STOVL aircraft are capable of taking off vertically from a spot on the deck, using the ramp and a running start is far more fuel efficient and permits a heavier launch weight. As catapults are unnecessary, carriers with this arrangement reduce weight, complexity, and space needed for complex steam or electromagnetic launching equipment, vertical landing aircraft also remove the need for arresting cables and related hardware. Russian, Chinese, and future Indian carriers include a ski-jump ramp for launching lightly loaded conventional fighter aircraft but recover using traditional carrier arresting cables and a tailhook on their aircraft.

The disadvantage of the ski-jump is the penalty it exacts on aircraft size, payload, and fuel load (and thus range); heavily laden aircraft can not launch using a ski-jump because their high loaded weight requires either a longer takeoff roll than is possible on a carrier deck, or assistance from a catapult or JATO rocket. For example, the Russian Su-33 is only able to launch from the carrier Admiral Kuznetsov with a minimal armament and fuel load. Another disadvantage is on mixed flight deck operations where helicopters are also present such as a US Landing Helicopter Dock or Landing Helicopter Assault amphibious assault ship a ski jump is not included as this would eliminate one or more helicopter landing areas, this flat deck limits the loading of Harriers but is somewhat mitigated by the longer rolling start provided by a long flight deck compared to many STOVL carriers.

National fleets

Chart comparing a range of aircraft and helicopter carriers, in order of longest (top left) to shortest (bottom right)

A total of 20 fleet carriers are in active service with ten navies. Additionally, the navies of Australia, Brazil, China, France, India, Italy, Japan, South Korea, Spain, Thailand and the United States also operate ships capable of carrying and operating multiple helicopters and STOVL aircraft.