Arresting gear in the context of "STOBAR"

An aircraft catapult is an acceleration device used to help fixed-wing aircraft reach liftoff speed (V_LOF) 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 (which have pontoons instead of wheeled landing gears and thus cannot utilize runways) 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 (notably the Hawker Hurricane) would sometimes be catapulted from "catapult-equipped merchant" (CAM) 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.

A landing helicopter dock (LHD) is a multipurpose amphibious assault ship that is capable of operating both as a helicopter carrier and as a dock landing ship. LHD vessels are built with a full-length flight deck similar in appearance to a light aircraft carrier to operate VTOL rotorcrafts such as utility/attack helicopters, tiltrotor aircraft (such as the MV-22 Osprey) and VSTOL fixed-wing aircraft (such as the AV-8 Harrier and the F-35B Lightning II), as well as a well dock for launching landing crafts and amphibious vehicles. Some recent designs, such as the Chinese Type 076 class, even support CATOBAR operations for light aircraft and UCAVs via aircraft catapults and arresting gears.

The United States Navy (USN) and the Royal Australian Navy (RAN) use the term as a specific hull classification symbol. Examples of this kind of ship include the USN's Wasp class, French Navy's Mistral class and ships of the Spanish Navy's Juan Carlos I class including those designs based on the class, such as the RAN's Canberra class. Other nations also use the designation for their vessels, such as the Republic of Korea Navy for its Dokdo class. The Type 075 and Type 076 classes of the People's Liberation Army Navy (PLAN), though only regarded as amphibious assault ships in their native China, are considered LHDs in NATO reporting names.