Optical landing system

An optical landing system (OLS) (nicknamed "meatball" or simply, "Ball") is used to give glidepath information to pilots in the terminal phase of landing on an aircraft carrier. From the beginning of aircraft landing on ships in the 1920s to the introduction of OLSs, pilots relied solely on their visual perception of the landing area and the aid of the Landing Signal Officer (LSO in the U.S. Navy, or "batsman" in the Commonwealth navies). LSOs used colored flags, cloth paddles and lighted wands. The OLS was developed after World War II and was deployed on U.S. Navy carriers from 1955. In its developed form, the OLS consists of a horizontal row of green lights, used as a reference, and a column of vertical lights. The vertical lights signal whether the aircraft is too high, too low, or at the correct altitude as the pilot descends the glide slope towards the carrier's deck. Other lights give various commands and can be used to require the pilot to abort the landing and "go around." The OLS remains under control of the LSO, who can also communicate with the pilot via radio.

An optical landing system has several related components: the lights used to give visual cues to approaching aircraft, the light control system, and the mounting system.

At least three sets of lights are used, regardless of the actual technology:

Additionally, some (particularly later) optical landing systems include additional lamps:

Collectively, the apparatus that the lights are mounted on is called "the lens". It is turned on/off and brightness is adjusted at the lens itself for ground based units, and remotely for shipboard units. In both cases, the lens is connected to a hand-controller (called the "pickle") used by the LSOs. The pickle has buttons that control the wave-off and cut lights.

For shore-based Optical Landing Systems, the lights are typically mounted on a mobile unit that plugs into a power source. Once set up and calibrated, there are no moving parts to the unit. Shipboard units are much more complicated as they must be gyroscopically stabilized to compensate for ship movement. Additionally, shipboard units are mechanically moved (the "roll angle") to adjust the touchdown point of each aircraft. With this adjustment, the tailhook touchdown point can be precisely targeted based on the tailhook-to-pilot's eye distance for each aircraft type.

The first OLS was the mirror landing aid, one of several British inventions made after the Second World War revolutionising the design of aircraft carriers. The others were the steam catapult and the angled flight deck. The Mirror Landing Aid was invented by Nicholas Goodhart. It was tested on the carriers HMS Illustrious and HMS Indomitable before being introduced on British carriers in 1954 and on US carriers in 1955.

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