Aircraft catapult

An aircraft catapult is a device used to help fixed-wing aircraft gain enough airspeed and lift for takeoff from a limited distance, typically from the deck of a ship. They are usually used on aircraft carrier flight decks as a form of assisted takeoff, but can also be installed on land-based runways, although this is rare.

The catapult used on aircraft carriers consists of a track or slot built into the flight deck, below which is a large piston or shuttle that is attached through the track to the nose gear of the aircraft, or in some cases a wire rope, called a catapult bridle, is attached to the aircraft and the catapult shuttle. Other forms 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 catapults 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. The United States Navy is developing the use of a linear motor-based electromagnetic catapult system called the Electromagnetic Aircraft Launch System (EMALS) with the construction of the Gerald R. Ford-class aircraft carriers, and a similar system has also been developed for the Chinese People's Liberation Army Navy's Type 003 aircraft carrier.

Historically it was most common for seaplanes to be catapulted, allowing them to land on the water near the vessel and be hoisted on board, although in the Second World War (before the advent of the escort carrier) conventional fighter aircraft (notably the Hawker Hurricane) would sometimes be catapulted from "catapult-equipped merchant" (CAM) vessels to drive off enemy aircraft, forcing the pilot to either divert to a land-based airstrip, or to jump out by parachute or ditch in the water near the convoy and wait for rescue.