(1)
(SSM 34-33-11).
(2)
(SSM 34-33-21).
(3)
(WDM 34-33-11).
(4)
(WDM 34-33-21).
E. Fault Isolation Procedure
(1) Use a time domain reflectometer (TDR) test set time domain reflectometer, COM-5187to do an electrical check of the coaxial cable and antenna:
CAUTION: YOU MUST PUT RF ABSORBENT MATERIAL ON THE ANTENNA BEFORE YOU USE THE TDR TEST SET. YOU CAN DAMAGE THE TEST SET IF A HIGH POWER TRANSMITTER OPERATES WITHIN 500 FEET OF THE ANTENNA.
(a)
Cover the applicable LRRA transmitter antenna with RF absorbent material.
(b)
Remove the applicable LRRA receiver/transmitter. To remove it, do this task: Low Range Radio Altimeter (LRRA) Receiver/Transmitter (R/T) Removal, AMM TASK 34-33-21-000-801.
(c)
Connect the TDR test set time domain reflectometer, COM-5187at pins 71 and C71 of the applicable connector at the LRRA receiver/transmitter (WDM 34-33-11, WDM 34-33-21).
LRRA TDR TEST SET CONNECTOR LRRA-1 (M1735) TDR TEST SET D3667B
TDR --------------------pin71 TDR --------------------pinC71
LRRA-2 (M1736) TDR TEST SET D3669
TDR --------------------pin71 TDR --------------------pinC71
EFFECTIVITY SIL ALL 34-33 TASK 803
D633A103-SIL BOEING PROPRIETARY -Copyright # Unpublished Work -See title page for details Page 208 Feb 15/2010
(d)
Do an electrical check of the coaxial cable and the antenna.
NOTE: The TDR test set has instructions which tell how to do the check of the cable and antenna.
(e)
Disconnect the TDR test settime domain reflectometer, COM-5187.
(f)
Re-install the LRRA receiver/transceiver. To install it, do this task: Low Range Radio Altimeter (LRRA) Receiver/Transmitter (R/T) Installation, AMM TASK 34-33-21-400-801.
(g)
If you find a problem with the coaxial cable, then do these steps: 1) Replace the applicable coaxial cable (WDM 34-31-11). 2) Do
this
task:
Low
Range
Radio
Altimeter
(LRRA)
BITE
Procedure,
34-33
TASK
801.
3) If the LCD display on the LRRA receiver/transmitter shows RADIO ALTIMETER TEST
COMPLETE NO FAILURES, then you corrected the fault.
(h)
If you find a problem with the antenna, do these steps:
1) Replace the applicable LRRA antenna. These are the tasks: Low Range Radio Altimeter (LRRA) Antenna Removal, AMM
TASK 34-33-11-000-801,
Low Range Radio Altimeter (LRRA) Antenna Installation, AMM
TASK 34-33-11-400-801. 2) Do
this
task:
Low
Range
Radio
Altimeter
(LRRA)
BITE
Procedure,
34-33
TASK
801.
3) If the LCD display on the LRRA receiver/transmitter shows RADIO ALTIMETER TEST
COMPLETE NO FAILURES, then you corrected the fault.
-------------------------END OF TASK ---------------------------
804. LRRA Receive Antenna Failed -Fault Isolation
A. Description
(1) The task is for this maintenance message:
(a) RECEIVE ANTENNA FAIL
B. Possible Causes
(1)
Receiver antenna, M1739 (No. 1) or M1740 (No. 2).
(2)
Wiring problem.
NOTE: Moisture contamination between the antenna and the airplane skin or in the antenna co-ax connector can cause false altitude output from the Radio Altimeter system.
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