UFC 3-535-01
17 November 2005
15-16.4
For the example shown by Figure 15-6 (high intensity runway edge light
for runways less than 60 meters (200 feet) wide), the inner or main beam ellipse is
defined by +5.5 degrees on the horizontal axis and +3.5 degrees and 3.5 degrees on
the vertical axis, while the outer ellipse is defined by +7.5degrees on the horizontal axis
and +6degrees on the vertical axis. Note that in Figure 4-2, the runway edge lights have
a wider beam ellipse for runways 60 meters (200 feet) or more wide, providing broader
light coverage. The runway edge lights are "toed-in" 3.5 degrees and aimed up 4
degrees above the horizontal. Threshold lights are parallel with the runway centerline
and aimed up 4.5 degrees. Other lights may also have a toe-in or aimed vertically
upward; however, this is identified separately and not indicated on the photometric
curves.
15-16.5
Photometric testing of new airfield lighting installations is being performed
more and more as a part of the acceptance testing of the overall system, and includes
the evaluation of a variety of factors in the lighting system being tested. While field
testing the photometrics of installed lights has not been practical in the past, current
available technology enables the testing of an entire system in a relatively short period
of time, testing each fixture, with good correlation to laboratory testing for meeting
photometric requirements. In addition to verifying the photometric performance of
installed light fixtures, proper testing can also help identify the following:
15-16.5.1
Possible leakage on the secondary side of the isolation transformer.
15-16.5.2
Improper alignment of fixtures.
15-16.5.3
Loose sockets and brackets.
15-16.5.4
If improper lamps have been installed.
15-16.5.5
Possible damage to lenses from sandblasting or other source of abrasion.
15-16.5.6
Improper current output from the constant current regulator.
15-16.5.7
These types of deficiencies may cause significant reductions in the
photometric output of a fixture, as well as the quality of the overall system performance.
The cost of photometric testing is relatively inexpensive compared with the cost of a
new airfield lighting system, while providing assurances for operational safety. The
testing can usually be performed with minimal disruption to airfield operations, and is
typically performed at night during periods of low or no aircraft traffic.
15-16.6
Photometric Testing of Existing Lighting Systems. This can provide
benefits similar to acceptance testing of new lighting systems. Typically, photometric
performance deteriorates over time, and periodic testing will provide an up-to-date
evaluation of performance. When photometric output is found to be below 50 percent to
70 percent of the minimum specified output, investigation should be made as to
possible cause and corrective action, whether by replacement or repair. Test results
269
Previous Page
