Optical Landing System - Components - Lights

Lights

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

• Datum lights — a horizontal row of green lamps used to give the pilot a reference against which he may judge his position relative to the glide slope.
• Ball (or “meatball”; also known as "the source") — indicates the relative position of the aircraft with reference to glide slope. If the aircraft is high, the ball will be above the datum lights; if the aircraft is low, the ball will be similarly below the datums. The further the aircraft is from the glide slope, the further the ball will be above or below the datum lights. If the aircraft gets dangerously low, the ball appears red. If the aircraft gets too high, the ball appears to go off the top.
• Wave-off lights — red flashing lamps which, when lit, indicate that the pilot must add full power and go around — a mandatory command. When the wave-off lights are lit, all other lamps are extinguished. The wave-off lights are operated manually by the LSO.

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

• Cut lights — Green lamps used to signal different things based on where the approaching aircraft is in its approach. Early in a no-radio or "zip-lip" approach (which is routine in modern carrier operations), Cut Lights are flashed for approximately 2–3 seconds to indicate that the aircraft is cleared to continue the approach. Subsequent flashes of the Cut Lights are used to prompt the pilot to add power. The longer the lights are left on, the more power should be added. Cut Lights are operated manually by the LSO.
• Emergency wave-off lights - Red lamps that have the identical function as Wave-Off Lights, but use an alternate power source. Not normally used.