UFC 3-535-01
17 November 2005
Overrun--An area on the approach side of the runway threshold which is stabilized or
paved but is not intended for normal operational use. It serves as a safety area for
aircraft which overrun the end of the runway or touch down short of the threshold.
Positive Slope--A slope of the approach light plane upward and outward from the
landing threshold.
Rigid Support--A support for elevated lights or other devices which has been designed
to support the lights under all foreseeable weather conditions without regard for impact
resistance. Do not use these supports in new construction for systems in safety
clearance zones or where there is present danger of impact by aircraft.
Runway Centerline--A line halfway between the edges of the surface designated for
normal aircraft landing and takeoff operations.
Runway Edge--The sides of a runway designated as full strength and capable of
supporting aircraft wheel loads; any area beyond that point is a non-operational area.
Runway End--The longitudinal limit of usable runway opposite the runway threshold. It
often, but not always, coincides with the threshold of the opposite direction runway
surface.
Runway Visual Range (RVR)--The maximum distance in the direction of take-off or
landing from which the runway (or the specified lights or markers delineating it) can be
seen from a position above a specified point on the runway centerline and at a height
corresponding to the average eye level of pilots at touchdown.
Semi-frangible Support--A two element support for light fixtures or other devices
designed for use in applications where the mounting is over 12 meters (40 feet) above
the ground and exceeds the design limits for low impact resistant supports mounted on
a rigid support and a means to lower the lights for servicing.
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