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 MIL-HDBK-1023/4
Section 5: PREVENTIVE MAINTENANCE
5.1
General. This chapter discusses the preventive maintenance program for the lighted
navigational aid facilities and equipment. It contains a preventive maintenance inspection
schedule (PMI) for major item of equipment with step-by-step instructions for performing the
PMI. The PMIs establish a recommended routine which may be altered to suit local conditions.
General troubleshooting procedure for facility lighting systems are contained in Section 6.
Corrective maintenance procedures for specific equipment will be found in the manufacturer's
operating and maintenance instructions.
5.2
Rotating Beacons Airfield, Helipads, and Heliports
5.2.1
Preventive Maintenance Inspection (PMI) Procedures. To perform the PMIs contained
in Table 6 proceed as follows:
a) Daily checks
(1) Check the operation of beacon. Verify beacon operation from dusk to dawn.
(2) Count the revolutions per minute (rpm) of beacon; should be either 6 or 12 rpm
1 rpm, depending on equipment type. Check for proper color and flash sequence. For military
airports the sequence is double peak white, single peak green. For helicopter facilities the
sequence is double peak white, single peak green and single peak yellow. For medical facilities
the sequence is double peak white, single peak green and single peak red.
(3) Check telltale indicator lamp to see if it is illuminated. If it is illuminated, it
indicates that the beacon is operating on the reserve (spare) lamp. The burned-out lamp should
be replaced immediately.
b) Bimonthly checks
(1) Lamp Changer. Check the operation of the lamp-changer. De-energize the
beacon circuit and remove the operating lamp from its receptacle. Energize the beacon circuit
and observe that the beacon changes to the reserve lamp. De-energize the beacon circuit and
reinstall the lamp previously removed.
(2) Slip Rings. Check the condition of the slip rings and brushes. Clean the slip
rings and brushes with a cloth moistened with trichloroethylene. If sparking or pitting has
occurred, smooth rings according to manufacturer's instructions. Avoid sanding; sanding
produces a raw copper surface which shortens brush life. If the slip rings are deeply pitted,
replace or have them turned down. Replace worn out brushes.
(3) Clutch. Test the clutch torque by hooking a spring scale in one of the handles
on the side of the housing. The clutch should slip between 8 to 10 pounds.
(4) Lens Retainer. Check the clamps or screws that secure the beacon lens (or
cover) in place to be sure they are tight, and the lens is properly seated.
(5) Telltale Light. Check the telltale light for a burned-out bulb. Clean glassware.
(6) Relays. Check the operation of the relay and clean relay contacts if they are
pitted or show evidence of poor contact. Replace relay if points are badly pitted.
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