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G. An alternate method of trouble shooting the glide slope antenna system coaxial cables with the use of a Time Domain Reflectometer is provided in 20-11-31/201, Coaxial Cable - Maintenance Practices.
H. Failure of a glide slope antenna coaxial relay can result in damage to the associated A/P accessory box and/or landing gear logic unit. Illumination of a "G/S ANT" annunciator (P2) indicates a glide slope antenna switching failure. The most probable cause of this type failure is one of the glide slope antenna coaxial relays listed in table 101.
CAUTION: DO NOT ACTIVATE A "GLIDE SLOPE ANT TEST" SWITCH ON
_______
PANEL P2 AFTER A GLIDE SLOPE ANTENNA SWITCHING FAILURE
HAS OCCURRED (G/S ANT ANNUNCIATOR ON PANEL P2
ILLUMINATED) AS THIS CAN RESULT IN FURTHER DAMAGE TO
THE ASSOCIATED A/P ACCESSORY BOX.
I. When a glide slope antenna switching failure has occurred, do the procedure in paragraph "J" before you do any of the other glide slope antenna system trouble shooting procedures. The procedure in paragraph "J" assumes that all affected wiring is OK, power is of the proper voltage, and annunciator light bulbs are OK.
J. Glide Slope Antenna Switching Trouble Shooting
(1)
Open GLIDE SLOPE 1 and 2 circuit breakers on the P7 panel and GLIDE SLOPE 3 circuit breaker on the P126.
(2)
Examine all glide slope antenna coaxial relays (switches) on panels P31 and P32 to determine that the serial number of each relay with a part number 910C31200 switch has the suffix "E" (i.e. 357E).
(3)
Replace all switches with a part number 910C31200 that do not have a suffix "E" in the serial number (AMM 34-31-10/401).
NOTE: If you replace the coaxial relay with a Transco coaxial relay
____ part number 910C31200, make sure that the serial number has a suffix "E".
(4) Replace drive card A08 in alternate landing gear logic unit M809 or drive card A14 in primary landing gear logic unit M93 for the corresponding illuminated G/S ANT annunciator listed in Table 101 (AMM 32-61-15/401).
EFFECTIVITY
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~êêêê G/S ANT AFFECTED AFFECTED AFFECTED ANNUN G/S ANT LDG GEAR AUTOPILOT CONDITION ILLUMINATED COAX RELAY LOGIC UNIT ACCESS BOX è””””. FAIL PASSIVE 1 2 (B405) ALTERNATE B195 SYSTEM NOSE (M809) LANDING GEAR 2 1 (B404) PRIMARY B194 or UP (M93) B195 è””””. FAIL-OP 1 2&3 ALTERNATE B420 SYSTEM (B405&B119) (M809) NOSE LANDING 2 1&3 PRIMARY B420 GEAR UP (B404&B119) (M93) 1&2 3 (B119) B420 1&3 2 (B405) ALTERNATE B195 (M809) 2&3 1 (B404) PRIMARY B194 (M93) éééé
Glide Slope Antenna Switching Trouble Shooting
______________________________________________ Table 101
(5) Apply power to all VOR/ILS navigation systems.
NOTE: Verify that AFCS is not engaged in VOR/LOC, ILS or LAND
____ mode with channel A, B or C in command or the glide slope antenna coaxial relay test will be inhibited.
(6)
Actuate GLIDE SLOPE ANT TEST switches 1, 2 and 3 (if installed) on panel P2 in turn. Check that G/S-1 ANT, G/S-2 ANT or G/S-3 ANT annunciator comes on when the associated TEST switch is actuated.
(7)
If annunciator(s) fails to come on in previous step, replace associated autopilot accessory box (Fig. 103). Refer to 22-11-03, Autopilot Accessory Boxes - Removal/Installation.
(8)
Repeat step (6).
2. Equipment and Materials_______________________ 中國航空網 m.k6050.com 航空翻譯 www.aviation.cn 本文鏈接地址：747飛機維護手冊AMM CHAPTER 34 - NAVIGATION 第34章導航2(46)
