UFC 3-535-01
17 November 2005
4-4.3
Medium Intensity Threshold Lights
Install threshold lights in a line perpendicular to the extended runway centerline outside
the usable landing area a distance of not more than 3 meters (10 feet). The line of lights
is symmetrical about the runway centerline and extends 12 meters (40 feet) outboard of
the lines of runway edge lights. (See Figure 4-4.) Determine the position of the lights as
follows:
4-4.3.1
Place a light where the line of threshold lights intersects the line of runway
edge lights. Next, place lights at 3 meters (10 feet) for a distance of 12 meters (40 feet)
outboard of the runway edge light lines.
4-4.3.2
If inboard lights are used, place lights at uniform intervals between the
lines of runway edge lights and along the line of the threshold lights. The interval must
be a maximum of 3 meters (10 feet).
4-4.4
Photometric Requirements
4-4.4.1
High Intensity Threshold Lights
Optimum aiming of lights depends on the design and output of the fixtures used in the
system. Light fixtures may be designed to cover several applications and may have
fixed patterns and aiming angles that differ from this document. Light aiming and
patterns other than those given in the standard may be used if the resultant light pattern
produces equivalent light intensities in the areas required by this standard. The lights
must be uni-directional green aimed into the approach with intensities as shown in
Figure 4-5 when used with high intensity runway edge lights or approach lights. The
light beams are aimed parallel with the runway centerline and angled upward at an
angle of 4.5 degrees. High intensity threshold lights must operate at five intensity levels,
together with the associated runway edge lights or approach lights when installed. High
intensity runway edge lights will be used with high intensity threshold lights.
4-4.4.2
Medium Intensity Threshold Lights
The lights must be bi-directional red/green, with green aimed towards the approach.
Outboard threshold elevated lights must be FAA L-861SE, and inboard threshold in-
pavement lights must be FAA L-852D. See FAA AC 150/5345-46 for additional
requirements.
4-4.5
Equipment
Inboard threshold lights use in-pavement fixtures with no part of the fixture protruding
more than 0.025 meters (1 inch) above the surrounding surface. Outboard threshold
lights use elevated fixtures, frangible mounted. Where the opposite direction runway
end is collocated with the threshold, runway end lights may be incorporated into
threshold light fixtures. The number of bi-directional fixtures must be the minimum
required to satisfy the requirement for end light fixtures. Where traffic patterns or
arresting gear equipment interfere with the use of elevated fixtures, in-pavement fixtures
must be used. (See paragraph 13-10.3.)
4-4.6
Power Requirements
55
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