Aircraft catapult
An aircraft catapult is a device used to launch aircraft
An aircraft is a vehicle that is able to fly by gaining support from the air, or, in general, the atmosphere of a planet. An aircraft counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines.Although...

 from ship
Since the end of the age of sail a ship has been any large buoyant marine vessel. Ships are generally distinguished from boats based on size and cargo or passenger capacity. Ships are used on lakes, seas, and rivers for a variety of activities, such as the transport of people or goods, fishing,...

s—in particular aircraft carrier
Aircraft carrier
An aircraft carrier is a warship designed with a primary mission of deploying and recovering aircraft, acting as a seagoing airbase. Aircraft carriers thus allow a naval force to project air power worldwide without having to depend on local bases for staging aircraft operations...

s—as a form of assisted take off
Assisted take off
Assisted take off is any system for helping aircraft into the air . The reason it might be needed is due to the aircraft's weight exceeding the normal maximum take off weight, insufficient power, or the available runway length may be insufficient, or a combination of all three factors...

. It consists of a track built into the flight deck
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...

, below which is a large piston or shuttle that is attached through the track to the nose gear
The undercarriage or landing gear in aviation, is the structure that supports an aircraft on the ground and allows it to taxi, takeoff and land...

 of the aircraft, or in some cases a wire rope called a catapult bridle is attached to the aircraft and the catapult shuttle.

The ramps at the catapult ends on some aircraft carriers are used to catch the ropes so they can be reused; bridles have not been used on U.S. aircraft since the end of the Cold War
Cold War
The Cold War was the continuing state from roughly 1946 to 1991 of political conflict, military tension, proxy wars, and economic competition between the Communist World—primarily the Soviet Union and its satellite states and allies—and the powers of the Western world, primarily the United States...

, and all U.S. Navy carriers commissioned since then have not had the ramps. The last U.S. carrier commissioned with a bridle catcher was USS Carl Vinson
USS Carl Vinson (CVN-70)
The USS Carl Vinson is the third United States Navy Nimitz class supercarrier and is named after Carl Vinson, a Congressman from Georgia. Carl Vinson's callsign is "Gold Eagle". It played host to the first NCAA basketball game on an aircraft carrier on 11/11/11 between the University of North...

; starting with USS Theodore Roosevelt
USS Theodore Roosevelt (CVN-71)
USS Theodore Roosevelt is the fourth Nimitz-class supercarrier. Her radio call sign is Rough Rider, the name of President Theodore Roosevelt's volunteer cavalry unit during the Spanish-American War...

 the ramps were deleted. During Refueling and Complex Overhaul
Refueling and Overhaul
In the United States Navy, Refueling and Overhaul refers to a lengthy process or procedure performed on nuclear-powered Naval ships, which involves replacement of expended nuclear fuel with new fuel and a general maintenance fix-up, renovation, and often modernization of the entire ship...

 refits in the late 1990s–early 2000s, the bridle catchers were removed from the first three Nimitz-class aircraft carrier
Nimitz class aircraft carrier
The Nimitz-class supercarriers are a class of ten nuclear-powered aircraft carriers in service with the United States Navy. With an overall length of and full-load displacements of over 100,000 long tons, they are the largest capital ships in the world...

s. USS Enterprise
USS Enterprise (CVN-65)
USS Enterprise , formerly CVA-65, is the world's first nuclear-powered aircraft carrier and the eighth US naval vessel to bear the name. Like her predecessor of World War II fame, she is nicknamed the "Big E". At , she is the longest naval vessel in the world...

 is the last U.S. Navy operational carrier with the ramps still attached.

At launch, a release bar holds the aircraft in place as steam pressure builds up, then breaks (or "releases"; older models used a pin that sheared), 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 (ship's speed plus or minus "natural" wind) will be sufficient to allow an aircraft to fly away, even after losing one engine.

First record flight using a catapult

Aviation pioneer 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
Wright brothers
The Wright brothers, Orville and Wilbur , were two Americans credited with inventing and building the world's first successful airplane and making the first controlled, powered and sustained heavier-than-air human flight, on December 17, 1903...

 beginning in 1904 used a weight
In science and engineering, the weight of an object is the force on the object due to gravity. Its magnitude , often denoted by an italic letter W, is the product of the mass m of the object and the magnitude of the local gravitational acceleration g; thus:...

 and derrick
A derrick is a lifting device composed of one tower, or guyed mast such as a pole which is hinged freely at the bottom. It is controlled by lines powered by some means such as man-hauling or motors, so that the pole can move in all four directions. A line runs up it and over its top with a hook on...

 styled catapult to assist their early aircraft with a takeoff in a limited space.

On 31 July 1912, Theodore Gordon Ellyson
Theodore Gordon Ellyson
Theodore Gordon Ellyson, USN , nicknamed "Spuds", was the first United States Navy officer designated as an aviator . Ellyson served in the experimental development of aviation in the years before and after World War I. He also spent several years before the war as part of the Navy's new...

 became the first person to be launched from the experimental catapult system. The U.S. Navy had been perfecting an air-compressed catapult system and mounted it on the Santee Dock in Annapolis, Maryland
Annapolis, Maryland
Annapolis is the capital of the U.S. state of Maryland, as well as the county seat of Anne Arundel County. It had a population of 38,394 at the 2010 census and is situated on the Chesapeake Bay at the mouth of the Severn River, south of Baltimore and about east of Washington, D.C. Annapolis is...

. The first attempt nearly killed Lt. 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, Lt. Commander. H. C. Mustin made the first catapult launch from a moving ship.

Interwar and World War II

In the late 1920s the passenger liners SS Europa and the SS Bremen
SS Bremen (1929)
The SS Bremen was a German-built ocean liner constructed for the Norddeutscher Lloyd line to work the transatlantic sea route. The Bremen was notable for her bulbous bow construction, high-speed engines, and low, streamlined profile. At the time of her construction, she and her sister ship were...

 of the Norddeutscher Lloyd
Norddeutscher Lloyd
Norddeutsche Lloyd was a German shipping company. It was founded by Hermann Henrich Meier and Eduard Crüsemann in Bremen on February 20, 1857. It developed into one of the most important German shipping companies of the late 19th and early 20th centuries, and was instrumental in the economic...

 line experimented with catapult launched mailplanes. Up to and during World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

 most catapults were hydraulic. 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 (conditions which afforded pilot
An aviator is a person who flies an aircraft. The first recorded use of the term was in 1887, as a variation of 'aviation', from the Latin avis , coined in 1863 by G. de la Landelle in Aviation Ou Navigation Aérienne...

s far less margin for error in the first moments of flight). They were mostly used for experimental purposes, and their use was entirely discontinued during the latter half of the war.

In the 1920s and 1930s, 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. There were submarine aircraft carriers, and some Japanese submarines used them for offensive operations also. The first launch off a Royal Navy
Royal Navy
The Royal Navy is the naval warfare service branch of the British Armed Forces. Founded in the 16th century, it is the oldest service branch and is known as the Senior Service...

 battlecruiser was from HMAS Australia
HMAS Australia (1911)
HMAS Australia was one of three s built for the defence of the British Empire. Ordered by the Australian government in 1909, she was launched in 1911, and commissioned as flagship of the fledgling Royal Australian Navy in 1913...

 on 8 March 1918. Subsequently many RN ships carried a catapult and from one to four aircraft; battleships or battlecruisers like the HMS Prince of Wales carried four aircraft and HMS Rodney carried two, while smaller warships like the cruiser HMNZS Leander
HMNZS Leander
HMNZS Leander was a light cruiser which served with the Royal New Zealand Navy during World War II. She was the lead ship of a class of eight ships, the Leander class light cruiser and was initially named HMS Leander.- History :...

 carried one. The aircraft carried were the Fairey Seafox or Supermarine Walrus
Supermarine Walrus
The Supermarine Walrus was a British single-engine amphibious biplane reconnaissance aircraft designed by R. J. Mitchell and operated by the Fleet Air Arm . It also served with the Royal Air Force , Royal Australian Air Force , Royal Canadian Air Force , Royal New Zealand Navy and Royal New...

. Some like HMS Nelson did not use a catapult, and the aircraft was lowered onto the sea for takeoff. Some had their aircraft and catapult removed during WWII e.g. HMS Duke of York
HMS Duke of York (17)
HMS Duke of York was a King George V-class battleship of the Royal Navy. Laid down in May 1937, the ship was constructed by John Brown and Company at Clydebank, Scotland, and commissioned into the Royal Navy on 4 November 1941, subsequently seeing service during the Second World War.In...

, or before (HMS Ramillies
HMS Ramillies (07)
HMS Ramillies was a Revenge-class battleship of the Royal Navy, named after the Battle of Ramillies. The ship is notable for having served in both the First and Second World Wars...


During World War II a number of ships were fitted with rocket-driven catapults, first the Fighter catapult ship
Fighter catapult ship
Fighter catapult ships also known as Catapult Armed Ships were an attempt by the Royal Navy to provide air cover at sea. Five ships were acquired and commissioned as Naval vessels early in the Second World War and these were used to accompany convoys....

s of the Royal Navy, then armed merchantmen
Armed merchantmen
Armed merchantman is a term that has come to mean a merchant ship equipped with guns, usually for defensive purposes, either by design or after the fact. In the days of sail, piracy and privateers, many merchantmen would be routinely armed, especially those engaging in long distance and high value...

 known as CAM ship
CAM ship
CAM ships were World War II-era British merchant ships used in convoys as an emergency stop-gap until sufficient escort carriers became available. CAM is an acronym for catapult aircraft merchantman. A CAM ship was equipped with a rocket-propelled catapult launching a single Hawker Sea Hurricane,...

s from "catapult armed merchantmen." These were used for convoy escort duties to drive off enemy reconnaissance bombers. CAM ships carried a Hawker Sea Hurricane, dubbed a "Hurricat" or "Catafighter", and the pilot bailed out unless he could fly to land.

Steam catapult

Although Deutsche Luft Hansa
Deutsche Luft Hansa
Deutsche Luft Hansa A.G. was a German airline, serving as flag carrier of the country during the later years of the Weimar Republic and throughout the Third Reich.-1920s:Deutsche Luft Hansa was founded on 6 January 1926 in Berlin...

 had utilized seaplane tenders using engine steam to launch their Dornier Do J
Dornier Do J
The Dornier Do J Wal was a twin-engine German flying boat of the 1920s designed by Dornier Flugzeugwerke. The Do J was designated the Do 16 by the Reich Air Ministry under its aircraft designation system of 1933....

 mailplanes on their South Atlantic Air Mail service as early as 1933, the modern steam catapult was a British
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

 invention. The use of steam to launch aircraft was suggested by Commander Colin C. Mitchell RNVR, and trials on HMS Perseus
HMS Perseus (R51)
HMS Perseus was a light fleet aircraft carrier built for the Royal Navy during World War II. The ship was initially named Edgar, but she was renamed in 1944 when the Admiralty decided to convert her into an aircraft maintenance carrier. She was completed in 1945, after the end of World War II, and...

 from 1950 showed its effectiveness. Navies introduced steam catapults, capable of launching the heavier jet
Jet aircraft
A jet aircraft is an aircraft propelled by jet engines. Jet aircraft generally fly much faster than propeller-powered aircraft and at higher altitudes – as high as . At these altitudes, jet engines achieve maximum efficiency over long distances. The engines in propeller-powered aircraft...

Fighter aircraft
A fighter aircraft is a military aircraft designed primarily for air-to-air combat with other aircraft, as opposed to a bomber, which is designed primarily to attack ground targets...

, in the mid-1950s. Powder-driven catapults were also contemplated, and would have been powerful enough, but would also have introduced far greater stresses on the airframes and may have been unsuitable for long use.

Nations that have retained large aircraft carriers and high performance CATOBAR
CATOBAR is a system used for the launch and recovery of aircraft from the deck of an aircraft carrier...

 (Catapult Assisted Take Off But Arrested Recovery) (the United States Navy
United States Navy
The United States Navy is the naval warfare service branch of the United States Armed Forces and one of the seven uniformed services of the United States. The U.S. Navy is the largest in the world; its battle fleet tonnage is greater than that of the next 13 largest navies combined. The U.S...

, Brazilian Navy
Brazilian Navy
The Brazilian Navy is a branch of the Brazilian Armed Forces responsible for conducting naval operations. It is the largest navy in Latin America...

, and French Navy
French Navy
The French Navy, officially the Marine nationale and often called La Royale is the maritime arm of the French military. It includes a full range of fighting vessels, from patrol boats to a nuclear powered aircraft carrier and 10 nuclear-powered submarines, four of which are capable of launching...

) are still using catapults out of necessity. Other navies operate STOVL
STOVL is an acronym for short take off and vertical landing.This is the ability of some aircraft to take off from a short runway or take off vertically if it does not have a very heavy payload and land vertically...

 aircraft, such the Sea Harrier
BAE Sea Harrier
The British Aerospace Sea Harrier is a naval VTOL/STOVL jet fighter, reconnaissance and attack aircraft, a development of the Hawker Siddeley Harrier. It first entered service with the Royal Navy in April 1980 as the Sea Harrier FRS1 and became informally known as the "Shar"...

 or AV-8B Harrier II
AV-8B Harrier II
The McDonnell Douglas AV-8B Harrier II is a second-generation vertical/short takeoff and landing ground-attack aircraft. An Anglo-American development of the British Hawker Siddeley Harrier, the Harrier II is the final member of the Harrier family that started with the Hawker Siddeley P.1127 in...

, which do not require catapult assistance, from smaller and less costly ships. The Russian Su-33 "Flanker-D"
Sukhoi Su-33
The Sukhoi Su-33 is an all-weather carrier-based air defence fighter designed by Sukhoi and manufactured by KnAAPO. It is a derivative of the Su-27 "Flanker" and was initially known as the Su-27K. The aircraft was first used in operations in 1995, aboard the carrier Admiral Kuznetsov...

 can take off from aircraft carriers without a catapult, albeit at a reduced fuel and armament load. 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
E-2 Hawkeye
The Grumman E-2 Hawkeye is an American all-weather, aircraft carrier-capable tactical airborne early warning aircraft. This twin-turboprop aircraft was designed and developed during the late 1950s and early 1960s by the Grumman Aircraft Company for the United States Navy as a replacement for the...

 and S-3 Viking
S-3 Viking
The Lockheed S-3 Viking is a four-seat twin-engine jet aircraft that was used by the U.S. Navy to identify, track, and destroy enemy submarines. In the late 1990s, the S-3B's mission focus shifted to surface warfare and aerial refueling. The Viking also provided electronic warfare and surface...

, require a catapult shot, inasmuch as their thrust-to-weight ratio is too low for a conventional rolling takeoff on a carrier deck.


The commonly-used steam catapult relies on the availability of large quantities of high-pressure steam found in the vast majority of 20th century capital ships. The steam charges a steam accumulator
Steam accumulator
A Steam accumulator is an insulated steel pressure tank containing hot water and steam under pressure. It is a type of energy storage device. It can be used to smooth out peaks and troughs in demand for steam. Steam accumulators may take on a significance for energy storage in solar thermal...

 so that it may be released faster than it can be produced by the ship.

The steam catapult consists of two slotted cylinders typically 18 inches in diameter. The cylinders contain free pistons connected to a shuttle which protrudes through a slot in the flight deck. The nose-wheel of the aircraft to be launched is attached to the shuttle by a launch bar.

On completion of the launch the piston is traveling at high speed and would cause damage if not stopped in a controlled fashion. This is done by a water brake, which is a horizontal dashpot
A dashpot is a mechanical device, a damper which resists motion via viscous friction. The resulting force is proportional to the velocity, but acts in the opposite direction, slowing the motion and absorbing energy. It is commonly used in conjunction with a spring...

 into which sea water is pumped with a swirling action as fast as it can flow out of the open end. The combination of the slight compressibility of the aerated water, the restriction as the water is expelled from the dashpot and the force produced by the expelled water hitting the front of the piston assembly serves to absorb the energy of the piston without damage. At that point a return mechanism readies the piston and shuttle for the next launch.


The size and manpower requirements of steam catapults place limits on their capabilities. A newer approach is the Electromagnetic Aircraft Launch System (EMALS). Electromagnetic catapults place less stress on the aircraft and offer more control during the launch by allowing gradual and continual acceleration. Electromagnetic catapults are also anticipated to require significantly less maintenance through the use of solid state components.

Linear induction motors have been experimented with before, such as Westinghouse's Electropult system in 1945. However at the beginning of the 21st century, navies again started experimenting with catapults powered by linear induction motor
Linear induction motor
A linear induction motor is an AC asynchronous linear motor that works by the same general principles as other induction motors but which has been designed to directly produce motion in a straight line....

s and electromagnet
An electromagnet is a type of magnet in which the magnetic field is produced by the flow of electric current. The magnetic field disappears when the current is turned off...

s. EMALs would be more energy efficient on nuclear powered
Nuclear marine propulsion
Nuclear marine propulsion is propulsion of a ship by a nuclear reactor. Naval nuclear propulsion is propulsion that specifically refers to naval warships...

 aircraft carriers and would alleviate some of the dangers posed by using pressurized steam. On gas-turbine
Gas turbine
A gas turbine, also called a combustion turbine, is a type of internal combustion engine. It has an upstream rotating compressor coupled to a downstream turbine, and a combustion chamber in-between....

 powered ships, an electromagnetic catapult would eliminate the need for a separate steam boiler for generating catapult steam. The U.S. Navy's upcoming Gerald R. Ford class carrier includes electromagnetic catapults in its design.

See also

  • Naval aviation
    Naval aviation
    Naval aviation is the application of manned military air power by navies, including ships that embark fixed-wing aircraft or helicopters. In contrast, maritime aviation is the operation of aircraft in a maritime role under the command of non-naval forces such as the former RAF Coastal Command or a...

  • Modern US Navy carrier operations

External links

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