Aircraft catapult

An aircraft catapult is an acceleration device used to help fixed-wing aircraft reach liftoff speed faster during takeoff, typically when trying to take off from a very short runway, as otherwise the aircraft engines alone cannot get the aircraft to sufficient airspeed quickly enough for the wings to generate the lift needed to sustain flight. Launching via catapults enables aircraft that typically are only capable of conventional takeoffs, especially heavier aircraft with significant payloads, to perform short takeoffs from the roll distances of light aircraft. Catapults are usually used on the deck of a ship — such as the flight deck of an aircraft carrier — as a form of assisted takeoff for navalised aircraft, but can also be installed on land-based runways, although this is rare.
Historically it was most common for seaplanes to be catapulted from ships onto nearby water for takeoff, allowing them to conduct aerial reconnaissance missions and be crane-hoisted back on board during retrieval, although by the late First World War their roles are largely supplanted by the more versatile biplanes that can take off and land on carrier decks unassisted. During the Second World War before the advent of escort carriers, monoplane fighter aircraft would sometimes be catapulted from "catapult-equipped merchant" vessels for one-way sorties to repel enemy aircraft harassing shipping lanes, forcing the returning pilot to either divert to a land-based airstrip, jump out by parachute, or ditch in the water near the convoy and wait for rescue. By the time fleet carriers became the norm in WW2, catapult launches have become largely unnecessary and carrier-based fighter-bombers would routinely perform self-powered takeoffs and landings off and onto carrier decks, especially during the naval aviation-dominated Pacific War between the United States and the Empire of Japan. However, escalating arms races during the Cold War accelerated the adoption of the heavier jet aircraft for naval operations, thus motivating the development of new catapult systems, especially after the popularization of angled flight decks further limited the practical distance available as takeoff runways. Nowadays, jet aircraft can launch from aircraft carriers via either catapults or ski-jump deck, and perform optics-assisted landing onto the same ship with help from decelerative arresting gears.
The catapult system used on modern aircraft carriers consists of a straight track or slot built into the flight deck, on top of which is a sliding piece called a shuttle, which protrudes above the deck and is hooked onto the nose gear of the aircraft; or in some cases a wire rope called a catapult bridle is attached between the aircraft and the catapult shuttle. When launching, the shuttle is driven forward by force mechanisms within the track system, "hurling out" the aircraft and imparting an additional propulsion on top of the aircraft's own engine thrust to help it accelerate. Other forms of catapult have been used historically, such as mounting a launching cart holding a seaplane on a long girder-built structure mounted on the deck of a warship or merchant ship, but most catapult systems share a similar sliding track concept.
Different means have been used to propel the catapult, such as weight and derrick, gunpowder, flywheel, compressed air, hydraulic, steam power, and solid fuel rocket boosters. Since the second half of the 20th century, steam catapults have been the mainstay form of aircraft carrier catapults, especially on the nuclear-powered supercarriers, and is the core component of the catapult-assisted takeoff but arrested recovery system. Into the 21st century, General Atomics has developed an alternating current linear motor-based electromagnetic catapult system called the Electromagnetic Aircraft Launch System, which is installed on the United States Navy's new s. A direct current-based electromagnetic catapult has also been developed by the People's Republic of China for the People's Liberation Army Navy's Type 003 aircraft carrier, as well as the upcoming Type 076 amphibious assault ship and Type 004 aircraft carriers.

History

First recorded flight using a catapult

and Smithsonian Secretary Samuel Langley used a spring-operated catapult to launch his successful flying models and his failed Aerodrome of 1903. Likewise the Wright Brothers beginning in 1904 used a weight and derrick styled catapult to assist their early aircraft with a takeoff in a limited distance.
On 31 July 1912, Theodore Gordon Ellyson became the first person to be launched from a U.S. Navy catapult system. The Navy had been perfecting a compressed-air catapult system and mounted it on the Santee Dock in Annapolis, Maryland. The first attempt nearly killed Lieutenant Ellyson when the plane left the ramp with its nose pointing upward and it caught a crosswind, pushing the plane into the water. Ellyson was able to escape from the wreckage unhurt. On 12 November 1912, Lt. Ellyson made history as the Navy's first successful catapult launch, from a stationary coal barge. On 5 November 1915, Lieutenant Commander Henry C. Mustin made the first catapult launch from a ship underway.

Application timeline

Feature	First seen	First demonstrated on	First commissioned carrier	Entry into service	Notes
Naval catapult	1915		USS Langley – compressed air – fly wheel – hydraulic	1922 1927 1934	Lt. Cmdr. Henry Mustin made the first successful launch on November 5, 1915,
Steam catapult	1950			1954	added to Hancock during her 1953 SCB-27C refit.
Electromagnetic catapult	2010	Lakehurst Maxfield Field		2017	General Atomics EMALS

Interwar and World War II

The US Navy experimented with other power sources and models, including catapults that utilized gunpowder and flywheel variations. On 14 December 1924, a Martin MO-1 observation plane flown by Lt. L. C. Hayden was launched from using a catapult powered by gunpowder. Following this launch, this method was used aboard both cruisers and battleships.
By 1929, the German ocean liners SS Bremen and Europa had been fitted with compressed-air catapults designed by the Heinkel aviation firm of Rostock, with further work with catapult air mail across the South Atlantic Ocean, being undertaken during the first half of the 1930s, with Dornier Wal twin-engined flying boats.
Up to and during World War II, most catapults on aircraft carriers were hydraulic. United States Navy catapults on surface warships, however, were operated with explosive charges similar to those used for guns. Some carriers were completed before and during World War II with catapults on the hangar deck that fired athwartships, but they were unpopular because of their short run, low clearance of the hangar decks, inability to add the ship's forward speed to the aircraft's airspeed for takeoff, and lower clearance from the water. They were mostly used for experimental purposes, and their use was entirely discontinued during the latter half of the war.
Many naval vessels apart from aircraft carriers carried float planes, seaplanes or amphibians for reconnaissance and spotting. They were catapult-launched and landed on the sea alongside for recovery by crane. Additionally, the concept of submarine aircraft carriers was developed by multiple nations during the interwar period, and through until WW2 and beyond, wherein a submarine would launch a small number of floatplanes for offensive operations or artillery spotting, to be recovered by the submarine once the aircraft has landed. The first launch off a Royal Navy battlecruiser was from on 8 March 1918. Subsequently, many Royal Navy ships carried a catapult and from one to four aircraft; battleships or battlecruisers like carried four aircraft and carried two, while smaller warships like the cruiser carried one. The aircraft carried were the Fairey Seafox or Supermarine Walrus. Some like did not use a catapult, and the aircraft was lowered onto the sea for takeoff. Some had their aircraft and catapult removed during World War II e.g., or before.
File:Phyrexian - Marina militare 012.jpg|thumb|An IMAM Ro.43 floatplane catapulted by a RM cruiser in the early 1940s
During World War II a number of ships were fitted with rocket-driven catapults, first the fighter catapult ships of the Royal Navy, then armed merchantmen known as CAM ships from "catapult armed merchantmen". These were used for convoy escort duties to drive off enemy reconnaissance bombers. CAM ships carried a Hawker Sea Hurricane 1A, dubbed a "Hurricat" or "Catafighter", and the pilot bailed out unless he could fly to land.
While imprisoned in Colditz Castle during the war, British prisoners of war planned an escape attempt using a falling bathtub full of heavy rocks and stones as the motive power for a catapult to be used for launching the Colditz Cock glider from the roof of the castle.
Ground-launched V-1s were typically propelled up an inclined launch ramp by an apparatus known as a Dampferzeuger.

Steam catapult

Following World War II, the Royal Navy was developing a new catapult system for their fleet of carriers. Commander C. C. Mitchell, RNVR, recommended a steam-based system using a slotted cylinder as an effective and efficient means to launch the next generation of naval aircraft. One motive was that the British ships were smaller than their American counterparts and so they had shorter catapult runs, making hydraulic catapults ineffective for launching the new heavier jet fighters. Trials on, flown by pilots such as Eric "Winkle" Brown, from 1950 showed its effectiveness. NATO navies introduced steam catapults based on the British design in the mid-1950s; the U.S. Navy was also motivated by the need to launch heavy nuclear-armed jet bombers such as the Douglas A-3 Skywarrior and by fatalities caused by flammable hydraulic fluid. Gunpowder-driven catapults were also contemplated, and would have been powerful enough, but would also have introduced far greater stresses on the airframes and might have been unsuitable for long use.
At launch, a release bar holds the aircraft in place as steam pressure builds up, then breaks, freeing the piston to pull the aircraft along the deck at high speed. Within about two to four seconds, aircraft velocity by the action of the catapult plus apparent wind speed is sufficient to allow an aircraft to fly away, even after losing one engine.
Nations that have retained large aircraft carriers, i.e., the United States Navy and the French Navy, are still using a CATOBAR configuration. U.S. Navy tactical aircraft use catapults to launch with a heavier warload than would otherwise be possible. Larger planes, such as the E-2 Hawkeye and S-3 Viking, require a catapult shot, since their thrust-to-weight ratio is too low for a conventional rolling takeoff on a carrier deck.