Aircraft Carrier Landings: “Fresnel Lens Optical Landing System” (FLOLS) 1968 US Navy Training Film

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Detailed description of the Fresnel Lens Optical Landing System (FLOLS) used on US aircraft carriers.

US Navy Training Film MN-10442a

FLOLS Operation (MN-10442b):

Originally a public domain film from the US Navy, slightly cropped to remove uneven edges, with the aspect ratio corrected, and one-pass brightness-contrast-color correction & mild video noise reduction applied.
The soundtrack was also processed with volume normalization, noise reduction, clipping reduction, and/or equalization (the resulting sound, though not perfect, is far less noisy than the original).

Wikipedia license:

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…

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 datum lights. 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…

The first OLS was the mirror landing aid, one of several British inventions…

Fresnel lens optical landing system (FLOLS)

Later systems kept the same basic function of the mirror landing aid, but upgraded components and functionality. The concave mirror, source light combination was replaced with a series of fresnel lenses. 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 Stabilization system. These systems are still in wide use on runways at US Naval Air Stations.

Improved fresnel lens optical landing system (IFLOLS)

The IFLOLS, designed by engineers at NAEC Lakehurst, NJ, keeps the same basic design but improves on the FLOLS, giving a more precise indication of aircraft position on the glideslope. 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 Improved Fresnel Lens Optical Landing System, IFLOLS, uses a fiber optic “source” light, projected through lenses to present a sharper, crisper light. This has enabled pilots to begin to fly “the ball” further away from the ship making the transition from instrument flight to visual flight smoother…