Optical landing system

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.

For shore-based optical landing systems, the lights are typically mounted on a mobile unit that plugs into a power source.

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.

A bright orange "source" light was shone into the mirror creating the "ball" (or "meatball" in later USN parlance) which could be seen by the aviator who was about to land.

The gyro stabilisation compensated for much of the movement of the flight deck due to the sea, giving a constant glidepath.

The Mk 6 Mod 3 FLOLS was tested in 1970 and had not changed much, except for when ship's heave was taken into account with an inertial stabilisation system.

A prototype IFLOLS was tested on board USS George Washington (CVN-73) in 1997, and every deploying aircraft carrier since 2004 has had the system.

The MOVLAS is a backup visual landing aid system used when the primary optical system (IFLOLS) is inoperable, stabilisation limits are exceeded or unreliable (primarily due to extreme sea states causing a pitching deck), and for pilot/LSO training.

Only the most experienced LSOs will perform talk downs or control aircraft with MOVLAS during heavy sea states.