In aeronautical terms, an aircraft carrier is a fully operational floating runway, with characteristics similar to those of an asphalt runway on land.
Aircraft carriers are one of the most iconic types of ships in existence. They are floating cities that can accommodate thousands of crew members on board. These mobile air bases are capable of transporting short-range fighter jets to any destination in the world. However, not all armed forces in the world have them; in fact, there are currently fewer than 40 operational aircraft carriers, spread across the navies of approximately a dozen countries.
The United States has by far the largest fleet, which includes several large-scale aircraft carriers (supercarriers) as well as some amphibious assault ships, which often carry helicopters.
Supercarrier
Supercarriers are the largest type of aircraft carrier currently in operation and, for now, are only in the possession of the US Navy, which has ten of them in its fleet. The British Navy has two of these vessels under construction, which will be ready in 2018. The Chinese Navy also has a supercarrier that is beginning to be built.
This type of aircraft carrier is approximately 300 metres long and can carry up to 80 fighter aircraft in various configurations.
The flight deck
The flight deck of an aircraft carrier is obviously the most important part of the ship and the centre of its activity, as it is the area where aircraft take off and land.
In aeronautical terms, an aircraft carrier is a fully operational floating runway, with characteristics similar to those of an asphalt runway on land. However, there is no doubt that there are several specific systems and design elements that are only found on these floating runways.
The first flight decks were wooden ramps built on the highest part of adapted warships. The first aeroplane took off from one of these warships in 1910, from the American USS Birmingham. Just ten years later, the first aircraft carriers resembling those of today began to appear, with a flight deck occupying the entire deck of the ship. The British ship HMS Argus had a specially constructed wooden platform along the entire length of the hull to facilitate unobstructed take-off and landing. However, this flight deck, which occupied the entire length of the ship's deck, meant that there was no structure or control tower from which to steer the ship, so this configuration was eventually replaced by the type of deck found on modern ships, which includes a tower on one side. This tower is used as a control centre for aircraft operations and as a command area from which the ship is steered.
The take-off and landing of aircraft are aspects that have also evolved with changes in flight deck design. On early aircraft carriers, it was actually the flight deck crew themselves who stopped landing aircraft by literally holding onto them. Later, the arresting wire system became commonplace, with arresting hooks installed on the aircraft to stop it in very short distances (in most cases, these systems can stop an aircraft travelling at almost 250 km/h in just two seconds). However, grabbing one of these arresting wires was no easy task and, contrary to popular belief, as soon as the aircraft touches the deck, the pilot increases the thrust of the engines to maximum. The reason is simple: on such a short runway, if something goes wrong with the arresting wires, the pilot must have enough thrust to take off again.
As for take-off, the most common system was to catapult the aircraft. It was the Wright brothers, in 1904, who tested the first catapult systems using a combination of weight and a loading mast. However, the catapult systems on today's aircraft carriers consist of a runway integrated into the flight deck surface with a piston or cable attached to the base of the aircraft to literally launch it down the runway at high speed. Various propulsion systems have been used, from steam and pressurised air to hydraulic systems and even gunpowder. New systems using electromagnetic technologies are currently being developed.
Other aircraft carriers also use a ski jump runway design. This type of flight deck, which is more suitable for STOVL (short take-off and vertical landing) aircraft, has the advantage of a shorter runway and converts the forward movement of the aircraft into an upward movement, with positive climb speed immediately after take-off.
Several different take-off and landing configurations have also been tested and used on aircraft carrier flight decks. In the mid-1940s, the Royal Navy tested the first angled flight decks. This deck was designed to accommodate a runway positioned at an angle to the axis, thereby maintaining a longer runway for jets with higher landing speeds, while optimising deck space to provide a larger tower area and the possibility of simultaneous take-off and landing operations. Among the most innovative versions of this design is a wider deck, which has become a common feature of modern supercarriers and aircraft carriers. Space is optimised to include a large control tower and simultaneous take-off and landing operations, as well as an aircraft parking area.
Optical landing systems
Without a doubt, landing on an aircraft carrier is one of the most difficult tasks pilots face in their careers; however, fortunately, technology has evolved to make it slightly easier. Given the extremely short length of aircraft carrier runways and the fact that traditional visual approach systems found on land runways do not exist at sea, a type of optical approach system has been developed over the years. On early aircraft carriers, pilots relied on their own visual judgement and the assistance of other crew members (also known as “landing signal officers”). Later, landing signal officers guided pilots by radio and by changing the colour and position of lights on the deck itself so that the pilot could turn around again if necessary.
Currently, pilots landing on an aircraft carrier have the advantage of a fully equipped optical landing system. This is a powerful lighting device installed on the flight deck that uses a system of green, amber and red lights to indicate to the pilot whether the aircraft's landing path is correct or not. A horizontal row of green lights indicates an optimal glide slope, while a series of vertical lights, which change colour, indicate to the pilot whether the aircraft is flying too high or too low. There are also other indicators that prompt the pilot to abort the landing or give other commands. There are different variations of optical landing systems, which use new and updated types of lenses, although they are all based on the same principle.
Key topics related to this post: airport infrastructure and defence systems.
