Flight deck

The flight deck of an aircraft carrier is the surface from which its aircraft take off and land, essentially a miniature airfield at sea. On smaller naval ships which do not have aviation as a primary mission, the landing area for helicopters and other VTOL aircraft is also referred to as the flight deck. The official U.S. Navy term for these vessels is "aviation capable ships".

Evolution

Early flight decks

The first flight decks were inclined wooden ramps built over the forecastle of naval warships. Eugene Ely made the first airplane take-off from a warship from USS "Birmingham" on 14 November 1910 and on 4 May 1912, Commander Charles Samson became the first man to take off from a ship which was underway when he flew his Short S27 off of HMS "Hibernia", which was steaming at convert|10.5|kn|km/h|0. Because the take-off speed of early aircraft was so low, it was possible for an aircraft to make a very short take off when the launching ship was steaming into the wind. Later, removable "flying-off platforms" appeared on the gun turrets of battleships and battlecruisers, allowing aircraft to be flown off for scouting purposes, although there was no chance of recovery.

On 2 August 1917, while performing trials, Squadron Commander Edwin Dunning landed a Sopwith Pup successfully on board the flying-off platform of HMS "Furious", becoming the first person to land an aircraft on a moving ship. However, on his second attempt, a tyre burst as he attempted to land, causing the aircraft to go over the side, killing him; thus Dunning also has the dubious distinction of being the first person to die in an aircraft carrier landing accident. The landing arrangements on "Furious" were highly unsatisfactory, however. In order to land, aircraft had to manoeuvre around the superstructure. "Furious" was therefore returned to dockyard hands have a 300 foot (91 m) deck added aft for landing, on top of a new hangar. However, the central superstructure remained, and turbulence caused by this badly affected the landing deck.

Full length decks

The first aircraft carrier that began to show the configuration of the modern vessel was the converted liner HMS "Argus", which had a large flat wooden deck added over the entire length of the hull, giving a combined landing and take-off deck unobstructed by superstructure turbulence. Because of her unobstructed flight deck, "Argus" had no fixed conning superstructure and no funnel. Rather, exhaust gasses were trunked down the side of the ship and ejected under the fantail of the flight deck (which, despite arrangements to disperse the gasses, gave an unwelcome "lift" to aircraft immediately prior to landing). The lack of a command position and funnel was unsatisfactory, and "Argus" was used to experiment with various ideas to remedy the solution. A photograph in 1917 shows her with a canvas mock-up of a starboard "island" superstructure and funnel. This was to starboard as the rotary engines of early aircraft caused a force to the left, meaning an aircraft naturally yawed to port on take-off, therefore it was desirable that they turned away from the fixed superstructure. This became the typical aircraft carrier arrangement and was used in the next British carriers, HMS "Hermes" and "Eagle".

After World War I, battlecruisers that otherwise would have had to have been discarded under the Washington Naval Treaty - such as the British HMS "Furious" and "Glorious" class and the American USS "Lexington" and "Saratoga" - were converted to carriers along the above lines. Being large and fast they were perfectly suited to this role; the heavy armouring and scantlings and low speed of the converted battleship "Eagle" served to be something of a handicap in practice. Because the military effectiveness of aircraft carriers was then unknown, early ships were typically equipped with cruiser-calibre guns to aid in their defence if surprised by enemy warships. These guns were generally removed during World War II and replaced with anti-aircraft guns, as carrier doctrine developed the "task force" (later called "battle group") model, where the carrier's defence against surface ships would be a combination of escorting warships and its own aircraft.

In ships of this configuration, the hangar deck was the strength deck, and an integral part of the hull, and the hangar and wooden flight deck were considered to be part of the superstructure. Such ships were still being built into the late 40s, classic examples being the US Navy's "Essex" and "Ticonderoga" class carriers. However, in 1936, the Royal Navy began construction of the "Illustrious" class. In these ships, the flight deck was now the strength deck, an integral part of the hull, and was heavily armoured to protect the ship and her air complement. Although the armoured carrier concept in this form remained something of a dead end, the flight deck as the strength deck was adopted for later construction. This was necessitated by the ever-increasing size of the ships, from the 13,000 ton USS Langley (CV-1) in 1922 to over a hundred thousand tons in the latest "Nimitz"-class carriers.

Armoured decks

When aircraft carriers supplanted battleships as the primary fleet capital ship, there were two schools of thought on the question of armour protection being included into the flight deck. The addition of armour to the flight deck offered aircraft below some protection against aerial bombs. However the extra space required did not allow the carriers to hang aircraft above, thus reducing the maximum number of airplanes carried.

Landing on flight decks

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thumb|Animated_representation_of_missed_approach_on_axial_flight_deck,_"Yorktown" class

Landing arrangements were originally primitive, with aircraft simply being "caught" by a team of deck-hands who would run out from the wings of the flight deck and grab a part of the aircraft to slow it down. This dangerous procedure was only possible with early aircraft of low weight and landing speed. Arrangements of nets served to catch the aircraft should the latter fail, although this was likely to cause structural damage. Landing larger and faster aircraft on a flight deck was made possible through the use of arresting cables installed on the flight deck and a tailhook installed on the aircraft. Early carriers had a very large number of arrestor cables or "wires". Current U.S. Navy carriers have three or four steel cables stretched across the deck at 20-foot (6 m) intervals which bring a plane, traveling at 150 miles per hour (240 kilometres per hour), to a complete stop in about 320 feet (98 m). The cables are set to stop each aircraft at the same place on the deck, regardless of the size or weight of the plane. During World War II, large net barriers would be erected across the flight deck in order that aircraft could be parked on the forward part of the deck and recovered on the after part. This allowed increased complements, but resulted in lengthened turn-around times as aircraft were shuffled around the carrier to allow take-off or landing operations.

Aircraft are given extra speed to assist take-offs by catapults.

Modern innovations

Angled flight deck

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thumb|Animated_representation_of_a_missed approach on angled flight deck, "Centaur" class showing how the offset recovery area allows for simultaneous launch and recovery operations.

With an angled flight deck (also referred to as a "skewed deck" or the "angle"), the aft part of the deck is widened and a separate runway is positioned at an angle from the centreline.cite web |url=http://www.navy.gov.au/The_angled_flight_deck |title=The angled flight deck |accessdate=2008-09-15 |work=Sea Power Centre Australia |publisher=Royal Australian Navy] The angled flight deck was designed with the higher landing speeds of jet aircraft in mind, which would have required the entire length of a centreline flight deck to stop. The design also allowed for concurrent launch and recovery operations, and allowed aircraft failing to connect with the arrestor cables to abort the landing, accelerate, and relaunch (or "bolt") without risk to other parked or launching aircraft. The redesign allowed for several other design and operational modifications, including the mounting of a larger island (improving both ship-handling and flight control), drastically simplified aircraft recovery and deck movement (aircraft now launched from the bow and re-embarked on the angle, leaving a large open area amidships for arming and fuelling), and damage control. Because of its utility in flight operations, the angled deck is now a defining feature of STOBAR and CATOBAR equipped aircraft carriers.

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thumb|left|Animated_representation_of_how_the_angled_flight_deck_allows_for_simultaneous_launch_and_recovery_operations_without_risk_of_aircraft_colliding_on_deck._"Nimitz" class" carrier USS "Dwight D. Eisenhower" illustrating how increasing the offset angle of a carrier's recovery area allows the use of two catapults during launch and recovery operations.
The angled flight deck was first tested on HMS "Triumph", by painting angled deck markings onto the centeline flight deck. Following successful trials, USS "Antietam" and HMS "Centaur" were modified with overhanging angled flight decks in 1953 and 1954 respectively. The U.S. Navy installed the decks as part of the SCB-125 upgrade for the "Essex" class and SCB-110/110A for the "Midway" class. In February 1955, HMS "Ark Royal" became the first carrier to be constructed and launched with the deck, followed in the same year by the lead ships of the British "Majestic" class (HMAS "Melbourne") and the American "Forrestal" class (USS "Forrestal").

ki-jump ramp

Another British innovation is the ski-jump ramp, which came about as means of improving take off for the VSTOL BAE Sea Harrier "jump-jet" on the small Invincible class aircraft carriers. The ski jump is a ramp which is curved upwards at its forward end. This converts the short run up available into vertical motion and reduces the fuel used at take-off compared to a vertical take off, and allows the aircraft to carry a higher payload. Because aircraft that use the ski-jump ramp are usually jump-jets, such carriers do not use angled flight decks. Similarly, the catapult and arrester wire are also not necessary. The ski-jump ramp is now used on several aircraft carriers world wide.

Flexible decks

An idea tested but never taken to completion was the "flexible deck". In the early jet age it was seen that by eliminating the landing gear for carrier borne aircraft the inflight performance would be improved. This led to the concept of a deck that would absorb the energy of landing, the risk of damaging propellers no longer being an issue though take off would require some sort of launching cradle. [http://www.thunder-and-lightnings.co.uk/scimitar/history.html Thunder and Lightnings - Scimitar] 21 May 2007 ] Test were carried out with a Sea Vampire, and Supermarine designed their Type 508 for rubber deck landing, but the flexible deck idea was found to be impracticable due to the loads imposed on both pilot and airframe when landing. The Supermarine Type 508 was subsequently developed into a 'normal' carrier aircraft, the Scimitar.

References

ee also

* Aircraft carrier
* Modern US Navy carrier operations