33-43-04
 ALL  ú ú 04 Page 206 ú Oct 18/01
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400 MAINTENANCE MANUAL
 ANTI-COLLISION LIGHTS - DESCRIPTION AND OPERATION
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 1.  General
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 A.  Strobe (xenon flashtube) anti-collision lights located on the top and bottom of the fuselage produce high intensity flashes at approximately 48 times per minute. Each light installation consists of a light assembly and a separate power supply unit.
 (1)  
The 115-volt ac ground service bus supplies power for anti-collision light operation through the BEACON lights switch on the P5 pilots overhead panel.

 (2)  
When BEACON lights switch is set to the BOTH position, upper and lower anti-collision lights will flash. When switch is set to LOWER position, the lower anti-collision light only will flash.

 B.  A strobe (xenon flashtube) anti-collision light is installed inside each forward wingtip fairing and on the tail cone below the APU exhaust port. The lights flash at approximately 48 flashes per minute. Each light installation consists of a light assembly and a separate power supply unit.
 (1)  The 115-volt ac ground service bus supplies power for anti-collision position light operation through the STROBE lights switch on the P5 panel. The strobe light power supply provides the timed high voltage pulses to cause the light to flash.
 WARNING:_______HIGH VOLTAGE PRESENT AT STROBE LIGHT COMPONENTS. WAIT 10 MINUTES AFTER REMOVING POWER BEFORE PERFORMING MAINTENANCE.
 C.  When performing maintenance on the anti-collision light system components, wait 10 minutes after power has been removed from system before handling components. This will permit high voltage capacitors to discharge.
 WARNING: DO NOT LOOK DIRECTLY AT FLASHING STROBE LIGHT FROM CLOSE RANGE.
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 LIGHT FLASHES MAY CAUSE MOMENTARY VISION IMPAIRMENT.

 D.  The high intensities of strobe light flashes may cause some eye discomfort if observed from a close range. Advise all personnel working in area close to strobe light(s) to avoid looking directly at strobe light when it is flashing.
 EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. ú

 33-44-00
 ALL  ú ú 01 Page 1 ú Feb 10/94
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400
MAINTENANCE MANUAL

 E.  For more data about this lighting system, refer to these sources:
 (1)
SSM 33-44-01 thru 33-44-99

 (2)
WDM 33-44-11 thru 33-44-99

 2.  Upper Anti-Collision Light
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 A.  The upper anti-collision light is located at station 568 beneath a red lens. The light installation is comprised of a light assembly, a power supply, and a cable assembly. Each light assembly contains a flashtube, a trigger coil, and a reflector. Each power supply assembly contains a transistorized power circuit and timing circuit. The unit develops the high voltage (approximately 500 volts) and timing sequence (approximately 48 cycles per minute) for flashtube operation. The power supply has two electrical connectors. One connector goes to airplane wiring and the other to the strobe light cable.
 3.  Lower Anti-Collision Light
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 A.  The lower anti-collision light is located at station 1148 on the bottom of the airplane fuselage. It is located on the keel beam area between the air conditioning compartment access doors. The light installation is similar to the upper anti-collision light.
 4.  Wingtip Anti-Collision Lights
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 A.  A strobe (xenon flashtube) anti-collision light is installed in each forward wingtip fairing behind a clear acrylic lens. A cable assembly connects the light to its power supply. The power supply is mounted in the outboard surface of the leading edge flap cavity. The light assembly is relamped by opening an access door on the lower wingtip fairing surface disconnecting the electrical connector, removing mounting screws, and removing light assembly. The power supply is replaced by extending and locking the outboard leading-edge flaps, disconnecting electrical connectors, removing mounting screws, and removing power supply.
 B.  Each light assembly contains a flashtube, a trigger coil, a reflector, and a clear rectangular lens. The reflector - lamp - lens arrangement directs the light beam so that it covers 70 degree arc in the vertical plane and a 140 degree arc in the horizontal plane.
　
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