Aircraft Carrier - Flight Deck

Flight Deck

As "runways at sea," modern aircraft carriers have a flat-top deck design that serves as a flight deck for the launch and recovery of aircraft. Aircraft launch forward, into the wind, and are recovered from astern. Carriers steam at speed, up to 35 knots (65 km/h) 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, plus it makes recovery safer by reducing the difference between the relative speeds of the aircraft and ship.

On CATOBAR carriers, a steam-powered catapult is used to accelerate conventional aircraft to a safe flying speed by the end of the catapult stroke, after which the aircraft is airborne and further propulsion is provided by its own engines. On STOVL or STOBAR carriers 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; though a STOVL is able to launch without a ski-jump or catapult with reduced fuel and weapon load. The form of assistance a carrier provides depends on the types of aircraft embarked and the design of the carrier itself.

Conversely, when recovering onto a CATOBAR or STOBAR carrier, conventional aircraft rely on a tailhook that catches on arrestor wires stretched across the deck to bring them to a stop in a short distance. Post WW-II Royal Navy research on safer CATOBAR recovery eventually lead 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. Helicopters and vertical/short take-off and landing (V/STOL) aircraft 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.

Conventional ("tailhook") aircraft rely upon a landing signal officer (LSO, sometimes called paddles) to monitor the plane'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.

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.

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." 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.

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 also allows simultaneous launching and recovery of aircraft, and the installation of one or two "waist" catapults in addition to the two bow cats.

The superstructure of a carrier (such as the bridge, flight control tower) are concentrated to the starboard side of the deck in a relatively small area called an island, a feature pioneered on the HMS Hermes in 1923. Very few carriers have been designed or built without an island. The flush deck configuration proved to have very significant drawbacks, complicating navigation, air traffic control, and had numerous other adverse factors.

A more recent configuration, originally developed by the Royal Navy but since adopted by many navies for most smaller carriers, has a ski-jump ramp at the forward end of the flight deck. A ski jump is a fixed ramp at the end of the flight deck with a curved incline. This was first developed to help launch short takeoff and vertical landing (STOVL) aircraft. STOVL aircraft such as the Sea Harrier can take off at far higher weights than is possible with a vertical or rolling takeoff on a short flat deck on STOBAR carriers. A ski-jump works by converting some of the forward rolling motion of the aircraft into a jump into the air at the end of the flight deck, the jump combined with the aiming of jet thrust partly downwards by swiveling exhaust nozzles on aircraft with this feature allows the heavily loaded and fueled aircraft 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. 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 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 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.

Unusual flight decks have been proposed for use in the jet age; from the SCADS conversion kit, to Skyhook, seaplane fighters, even a rubber flight deck. Shipborne containerized air-defense system (SCADS) was a proposed modular kit to convert a Ro-Ro or Container ship into a STOVL aircraft carrier in two days during an emergency with thirty days of jet fuel, munitions, defensive systems and missiles, ASW helicopters, crew and work areas, radar, and a ski jump, it could be quickly removed afterwards for storage, it was effectively a modern merchant aircraft carrier. Skyhook was proposed by British Aerospace and even more ambitious, a system using a crane with a top mating mechanism hung over the sea to fuel, launch, and recover a few Harriers even from ships as small as frigates. The Convair F2Y Sea Dart was a supersonic seaplane jet fighter that had skis rather than wheels, in the late 1940s the Navy feared that supersonic aircraft would not be able to land on a carrier, it would rather be lowered and raised from the sea via crane. The HMS Warrior tested a rubber coated flight deck where de Havilland Vampire fighters landed without needing landing gear or tailhook.