33-41-02
 ALL  ú ú 01 Page 403 ú Oct 10/95
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400 MAINTENANCE MANUAL
 LANDING, RUNWAY TURNOFF, AND NOSE GEAR TAXI LIGHTS - DESCRIPTION AND OPERATION
______________________________________________________________________________
 1.  General_______
 A.  The landing, runway turnoff, and nose gear taxi lights consist of:
 (1)  
Four landing lights flush mounted in individual wing cavities aft of each wing leading edge.

 (2)  
Two runway turnoff lights mounted on the nose gear lower tripod brace by the service interphone panel.

 (3)  
Two nose gear taxi lights mounted on the shock strut outer cylinder slightly above the service interphone panel.

 B.  For more data about this lighting system, refer to these sources:
 (1)  
SSM 33-42-01 thru 33-42-99

 (2)  
WDM 33-42-11 thru 33-42-99

 2.  Landing Lights______________
 A.  The four landing lights use halogen sealed beam lamps and are mounted behind curved heat resistant glass lenses in the leading edge of the wings. The inboard and outboard landing lights in each wing are adjacent to each other with two landing light transformers mounted between them. The light beams are adjustable plus or minus 5 degrees in each axis.
 B.  The 115 volt ac buses 1 and 3 supply primary power to the landing light transformers.
 (1)  
AC bus No. 1 supplies power to the left and right inboard landing lights through a circuit breaker on the P414 power distribution center - left.

 (2)  
AC bus No. 3 supplies power to the left and right outboard landing lights through a circuit breaker on the P415 power distribution center - right.

 (3)  
AC power to landing light transformers are controlled by switches on the P5 pilots overhead panel.

 C.  An automatic landing light dimming circuit reduces voltages across the landing light lamps whenever the landing gear lever is in the UP position. Moving the landing gear lever from DWN to UP position provides a ground path to energize relay R84 which then provides ground paths to energize two landing light dimming relays R1041 and R1042. The landing light relays switch the 115 Volts ac inputs to alternate taps on the landing light transformers causing the transformer secondary voltages to be reduced.
 3.  Runway Turnoff Lights_____________________
 A.  The two runway turnoff lights use sealed beam incandescent lamps and are mounted in the nose wheel light control panel housing on the nose gear. The lamps are aimed approximately 65 degrees left and right of the airplane centerline.
 B.  The 115-volt ac ground service bus supplies power to the runway turnoff lights transformers which provide 28 volts ac to the lights for light operation. When energized the runway turnoff lights relays turn the lights on. The 115-volt ac ground service bus, circuit breakers, transformers, and relays are all located in the P414 panel.
 (1)  Each runway turnoff light transformer output is protected by a secondary circuit breaker located in the P414 panel.
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 33-42-00
 ALL  ú ú 02 Page 1 ú Feb 10/94
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400
MAINTENANCE MANUAL

 C.  A ground safety relay in the P414 panel prevents the lights from coming on when the landing gear is retracted. 115 volts ac ground service buss supplies power to energize the runway turnoff lights relays through the ground safety relay.
 D.  The RUNWAY TURNOFF (L and R) switches on the P5 pilots' overhead panel control the lights. If the airplane is on the ground and the ground safety relay is energized, 115 volts ac is connected to the runway turnoff light relays through the ground safety relay. Setting either switch to the ON position will connect the applicable runway turnoff light relay coil to ground, energize the runway turnoff light relay, and supply 28 volts ac to the light.
 4.  Nose Gear Taxi Lights
_____________________
 A.  The two nose gear taxi lights use sealed beam incandescent lamps and are mounted on the fixed portion of the nose gear. The lamps are aimed left and right of the airplane centerline.
 B.  The 115-volt ac bus No. 1 supplies power through the nose gear taxi lights relay to a voltage reduction transformer. The transformer supplies 28 volts ac to the lamps. Secondary circuit breakers are provided between the transformer and the lights. The transformer, relay, and circuit breakers are located in the P414 panel. 115 volts ac from bus No. 1 supplies power to the taxi lights relay through the ground safety relay. This prevents system operation when the airplane is in flight. The ground safety relay is located in the P414 panel.
　
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