UFC 3-535-01
17 November 2005
3-1.3.3
300 meter (1,000 foot) Crossbar
This crossbar consists of two barrettes in aviation white lights located symmetrically
about and perpendicular to the system centerline at station 10+00 and in line with the
centerline barrette at that station. Each barrette consists of 8 lights on 1.5 meter (5 foot)
spacing with the outermost light located 15 meters (50 feet) from the system centerline.
3-1.3.4
Centerline Lights
The centerline lights consist of a series of barrettes in aviation white lights located at 30
meter (100 foot) intervals along the system centerline, from station 1+00 to station
30+00. Each barrette consists of five lights spaced at 1 meter (3.5 feet) on centers,
centered on and perpendicular to the system centerline. Centerline lights installed on
elevated supports may be spaced at 1.02 meters (40.5 inches) in order to fit standard
support hardware.
3-1.3.5
Sequenced Flashing Lights (SFL)
The sequenced flashing lights are a series of flashing lights located on the system
centerline at each station, beginning at station 10+00, 300 meters (1,000 feet) to the
end of the system at station 30+00. The lights flash a bluish-white light at a rate of twice
per second in sequence from the outermost light station toward the threshold, appearing
as a ball of white light traveling toward the runway. Sequenced flashing lights may be
uniformly mounted a maximum of 1.3 meters (4 feet) below the steady burning lights or,
when in-pavement lights are used, they may be displaced a maximum of 1.5 meters (5
feet) into the approach along the system centerline in order to avoid visual or physical
interference between light units.
3-1.3.6
Threshold Lights
While threshold lights are not actually a section of the approach light system, they must
be present and installed according to paragraph 4-4.
3-1.4
Photometrics
Optimum aiming of lights depends on the design and light 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 which differ from the standard. Light aiming and
patterns other than those given in this standard may be used, provided the resultant
light pattern produces equivalent light intensities in the areas required by the standard.
Luminous characteristics for the lights used in this system are described below. The
beam widths are measured symmetrically about the optical axis of the light unit unless
otherwise noted. All steady burning lights used in the system must meet the intensity
requirements given in Figure 3-2. Sequenced flashing lights must provide, at the
maximum intensity setting, an effective intensity of 15,000 candelas (cd) in an elliptical
area subtending beam angles of 15 degrees horizontally and 5 degrees measured
vertically from the beam axis.
3-1.4.1
Intensity Control
Provide brightness control with five intensity steps for steady burning lights and three
intensity steps for flashing lights. Couple the intensity of the sequenced flashing lights to
the intensity of the steady burning lights as follows:
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