Aircraft catapult
Encyclopedia : A : AI : AIR : Aircraft catapult
An aircraft catapult is a device used to launch aircraft from ships — in particular aircraft carriers — as a form of assisted take off. This type of catapult consists of a track built into the flight deck, below which is a large piston or shuttle that attaches up through the track to the nose gear of the aircraft. Older aircraft did not have a tow bar integrated in the nose gear; instead, a metal framework called a brindle was attached to the aircraft and the catapult shuttle. The ramps at the catapult ends on older carriers were used to catch these frameworks so they could be reused; brindles have not been used on aircraft since the end of the Cold War and all carriers commissioned since then have not had the ramps. 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 4 seconds, aircraft velocity plus apparent wind speed (ship's speed plus "natural" wind) will be sufficient to allow an aircraft to fly away, even after losing one engine.
History
The steam catapult was a British invention . Up to and during World War II most catapults were hydraulic. There were a number of armed merchantmen known as CAM ships from "catapult armed merchantmen" these were driven by a rocket. The use of steam to drive the aircraft forward came at the suggestion of a Commander Mitchell RNVR and trials on HMS Perseus from 1950 showed its effectiveness and navies introduced these steam catapults in the mid 1950s, which were the only ones capable of launching the heavier jet fighters. At the beginning of the 21st century, navies started experimenting with catapults powered by linear induction motors and electromagnetics. If large warships move from nuclear and steam power to gas turbines the resultant loss of readily-available high-pressure steam may drive a trend toward electomagnetic catapults. Some recent as yet unbuilt carrier designs include electric catapults.Those nations which have retained large aircraft carriers and high performance CATOBAR (Catapult Assisted Take Off But Arrested Recovery) or CTOL (Conventional Take Off and Landing) aircraft (United States Navy, Russian Navy and French Navy) are still, of necessity, using catapults. Other navies that have chosen not to afford large carriers operate STOVL aircraft which do not require catapult assistance like the Sea Harrier or AV-8B Harrier II off smaller and cheaper ships. Russian Sukhoi Su-33 can take off from aircraft carriers without an aircraft catapult, albeit at reduced fuel and armament load. US Navy tactical aircraft use catapults to launch with a heavier warload than would be possible otherwise. Larger planes, such as the E-2 Hawkeye and S-3 Viking, require a catapult shot as their thrust-weight ratio is too low for a conventional rolling takeoff in the small amount of space available on a carrier deck.
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