Editing Aircraft carrier (section)

==Description==
===Structure===
Carriers are large and long ships, although there is a high degree of variation depending on their intended role and [[air wing|aircraft complement]]. The size of the carrier has varied over history and among [[navy|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 aircraft carriers are notable for having [[nuclear reactor]]s powering their systems and propulsion.

[[File:DeHavilland Vampire HMS Ocean Dec1945 NAN1 47.jpg|thumb|The first carrier landing and take-off of a jet aircraft: [[Eric "Winkle" Brown]] landing on {{HMS|Ocean|R68|6}} in 1945]]
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 the [[Funnel (ship)|funnel]], air-traffic control and the [[bridge (nautical)|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 US Navy fleet carriers as it allows the deployment of heavy jets with full load-outs, 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]].

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.<ref>{{cite web|title=How Aircraft Carriers Work|website=How Stuff Works|first=Tom|last=Harris|date=29 August 2002|url=http://science.howstuffworks.com/aircraft-carrier6.htm|url-status=live|archive-url=https://web.archive.org/web/20131006205343/http://science.howstuffworks.com/aircraft-carrier6.htm|archive-date=6 October 2013}}</ref>

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

===Flight deck===
{{Main|Flight deck}}
[[File:US Navy 081124-N-3659B-305 F-A-18C Hornets launch from the Nimitz-class aircraft carrier USS Ronald Reagan (CVN 76).jpg|thumb|[[Aircraft catapult|Catapult]] launches aboard {{USS|Ronald Reagan}}]]

As "runways at sea", aircraft carriers have a flat-top [[flight deck]], which [[Takeoff|launches]] and [[landing|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 size of the vessel is a fundamental limitation on runway length. This affects take-off procedure, as a shorter runway length of the deck requires that aircraft [[Acceleration|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 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:
* [[CATOBAR|Catapult Assisted Take-Off Barrier Arrested Recovery]] (CATOBAR): A steam- or electric-powered [[Aircraft catapult|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.
* [[STOBAR|Short Take-Off Barrier 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.
* [[STOVL|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 (aviation)|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 [[BAe 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 [[Lockheed Martin F-35 Lightning II|Lockheed F-35B Lightning II]], which demonstrated VTOL capability in test flights but is operationally STOVL or in the case of UK uses "[[shipborne rolling vertical landing]]".
* [[VTOL|Vertical Take-Off and Landing]] (VTOL): Certain 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 due to the additional weight from associated systems.

On the recovery side of the flight deck, the adaptation to the aircraft load-out 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-World War II 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.<ref>{{Cite web|title=Why Aircraft Carriers Have an Angled Runway|date=2 November 2017|url=https://www.popularmechanics.com/military/navy-ships/a28881/aircraft-carriers-angle-runway/}}</ref>

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. [[Helicopter]]s and aircraft capable of vertical or short take-off and landing ([[V/STOL]]) usually recover by coming abreast of 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====
[[File:F-18 - A 3-wire landing.ogv|thumb|left|F/A-18 Hornet aircraft landing video]]

Carriers steam at speed, up to {{convert|35|kn|lk=in}} 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 (aviation)|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 the [[optical landing system]] have provided information on proper [[glide slope]], but LSOs still transmit voice calls to approaching pilots by radio.

Key personnel involved in the flight deck include the shooters, the handler, and the air boss. Shooters are [[naval aviator]]s or [[naval flight officer]]s 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".<ref>{{cite web|url=http://www.navy.mil/navydata/ships/carriers/powerhouse/powerhouse.asp|title=The US Navy Aircraft Carriers|publisher=United States Navy|access-date=30 January 2009|url-status=dead|archive-url=https://web.archive.org/web/20090221142917/http://www.navy.mil/navydata/ships/carriers/powerhouse/powerhouse.asp|archive-date=21 February 2009}}</ref> 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 US 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====
[[File:US Navy 100512-N-8446A-004 An F-A-18F Super Hornet assigned to the Fighting Checkmates of Strike Fighter Squadron (VFA) 211 lands aboard the aircraft carrier USS Enterprise (CVN 65).jpg|thumb|Island control structure of {{USS|Enterprise|CVN-65|6}}]]
[[File:FS CDG bridge3.jpg|alt=|thumb|The command bridge of the aircraft carrier {{ship|French aircraft carrier|Charles de Gaulle||2}}]]

The superstructure of a carrier (such as the [[bridge (ship)|bridge]], flight [[control tower]]) are concentrated in a relatively small area called an ''island'', a feature pioneered on {{HMS|Hermes|95|6}} in 1923. While the island is usually built on the [[starboard]] side of the flight deck, the Japanese aircraft carriers {{ship|Japanese aircraft carrier|Akagi||2}} and {{ship|Japanese aircraft carrier|Hiryū||2}} had their islands built on the [[Port and starboard|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|CV-1|6}}. 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.{{sfn|Friedman|1983|pp=241–243}}

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|short take off vertical landing]] (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 downward. 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 [[Stall (flight)|stalling out]] or crashing directly into the sea.

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 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 cannot 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 [[Sukhoi Su-33]] is only able to launch from the carrier {{ship|Russian aircraft carrier|Admiral Kuznetsov||2}} with a minimal armament and fuel load. Another disadvantage is on mixed flight deck operations where helicopters are also present, such as on 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.