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Fresnel Lens
17-APR-2008 Walter O. Koenig

Fresnel Lens

USS Midway Aircraft Carrier Museum view map

The Fresnel lens optical landing system provides guidance for correctly landing on an aircraft carrier.
The lens is located on the side of the runway so that it can be seen by the pilots throughout the entire landing process.

The optical landing system consists of a horizontal bar of green lights and a vertical bar of red lights on both sides of the "meatball". The "meatball" is the centerpiece that consists of five amber colored lenses.
Certain lenses will light up one at a time depending on the angle the plane is in relation to the "meatball." This causes the center light to appear to be moving up and down in relation to the horizontal green bars on the sides.
In order to safely land, the pilot tries to keep the center amber lens horizontal with the green bar throughout process .
If the pilot gets too low, the amber light will turn red indicating that the aircraft is dangerously low and risks hitting the back end of the aircraft carrier.
The red lights around the green horizontal bars will be flashing if the carrier is not able to receive the aircraft, and so the jet must keep circling or find another place to land.

From Illumin Volume 9: Issue ii, USC School of Engineering.


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Mike H.25-Nov-2011 22:48
Works a little like the PDI lights on our aerial refueling tankers. Neat info; thanks!
LynnH06-Aug-2009 22:09
Those pilots needed all the help they could get. Thanks for attaching this narrative. Fascinating stuff. V
pkocinski16-Jul-2009 22:44
Wow I never knew that!
Zeke 02-Jun-2008 16:54
Just to add one more detail about this system, through a series of synchros and servomotors, that are driven by a mechanical analog computer that receives pitch and roll data from the ship's gyro, the center set of light boxes (the meatball) is actually in motion and compensates for the motion of the flight deck giving the pilot a stablized reference point. (I'm a bit amazed at that I remember this after a quarter of a century of being away from it!)
Peter Sussex30-May-2008 19:30
Thanks for the detailed explanation, really broadened my mind.
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