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 MIL-HDBK-1023/4
b) Check of adapter unit current output
(1) With system on, adjust day current to 6.4 to 6.6 amperes.
(2) Cover photocell with a heavy glove or other dark material, wait for time delay
to de-energize, and read current. If the system has a night adjustment, set current to 4.8 to 5.0
amperes.
(3) Remove covering from photocell. The lights should switch back to day
brightness after a short time delay (15 seconds to 1 minute).
5.8.3
Visual Approach Slope Indicator (VASI). Some facilities have VASI systems which
are currently being replaced with PAPI systems. The procedures in Table 14 are applicable, for
the most part, for VASI as well. Check the manufacturer's maintenance manual for unique
procedures applicable for the system installed, as most are old and replacement parts are not
always available.
5.9
Airfield Beacons and Obstruction Lights
5.9.1
Preventive Maintenance Inspection Procedures. To perform the PMIs contained in
Table 15, proceed as follows:
a) Daily Checks. Verify that all hazard beacons and obstruction lights are burning
each night. Replace burned-out lamps.
b) Monthly checks
(1) For flashing hazard beacons, count the number of flashes of the hazard beacon
over a full 2-minute period. The flashing rate may range from 20 to 40 per minute; the beacon
"OFF" time should be about half the "ON" time.
(2) Check the operation of the photocell or other automatic control devices.
c) Semiannual Check. Test the insulation resistance of feeder cables and ground
resistance of the grounding system (refer to par. 4.7).
d) Annual checks
(1) Check the condition of the wire, insulation, splices, switches, connections and
fuses. Check the fuse size (should not be more than 120 percent of rated load). The fuse holder
should be tight with clean, uncorroded contacts. Check the wiring for loose connections and the
insulation for breaks or fraying. Check switches for loose, burned, or misaligned contacts.
(2) Check the lamp voltage at the lamp socket and record the voltage. Compare the
voltage with the previous reading. If the voltage reading is more than 10 percent different from
the nominal value, determine the cause and correct the problem. If a booster transformer is used,
check the input and output voltage levels.
(3) Check gaskets and seals for leaks. Adequate weatherproofing is necessary for
the protection of lights. All gaskets should be renewed when cracked or deteriorated. Before
installing a new gasket, thoroughly clean the gasket channel to make the gasket seat properly.
When it is necessary to secure the gasket with rubber cement, both gasket and seal should be
coated with cement and permitted to dry until tacky before the gasket is placed in position.
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