(a) LRU STATUS
(2)
The radio altimeter receiver/transmitter has an internal failure.
B. Possible Causes
(1) LRRA receiver/transmitter, M1735 (No. 1) or M1736 (No. 2).
C. Circuit Breakers
(1) These are the primary circuit breakers related to the fault:
CAPT Electrical System Panel, P18-1
Row Col Number Name
B 4 C01384 RADIO NAVIGATION RADIO ALTM 1
F/O Electrical System Panel, P6-1
Row Col Number Name
A 16 C01385 RADIO NAVIGATION RADIO ALTM 2
D. Related Data
(1)
(SSM 34-33-11).
(2)
(SSM 34-33-21).
(3)
(WDM 34-33-11).
(4)
(WDM 34-33-21).
E. Initial Evaluation
(1) Do
this
task:
Low
Range
Radio
Altimeter
(LRRA)
BITE
Procedure,
34-33
TASK
801.
(a)
If the red LRU STATUS light comes on, then do the Fault Isolation Procedure below.
(b)
If the red LRU STATUS light does not come on, then there was an intermittent fault.
F. Fault Isolation Procedure
(1) Replace the LRRA receiver/transmitter, M1735 (No. 1) or M1736 (No. 2).
These are the tasks:
EFFECTIVITY
34-33 TASKS 805-806
SIL ALL
Page 213 D633A103-SIL Jun 15/2010
Low Range Radio Altimeter (LRRA) Receiver/Transmitter (R/T) Removal, AMM TASK 34-33-21-000-801,
Low Range Radio Altimeter (LRRA) Receiver/Transmitter (R/T) Installation, AMM TASK 34-33-21-400-801.
(a) If the LRU STATUS light does not come on, then you corrected the fault.
-------------------------END OF TASK ---------------------------
807. LRRA Transmit Antenna Failed -Fault Isolation
A. Description
(1) The task is for this maintenance message:
(a) XMIT ANT FAIL
B. Possible Causes
(1)
Transmitter antenna, M1737 (No. 1) or M1738 (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.
C. Circuit Breakers
(1) These are the primary circuit breakers related to the fault:
CAPT Electrical System Panel, P18-1
Row Col Number Name
B 4 C01384 RADIO NAVIGATION RADIO ALTM 1
F/O Electrical System Panel, P6-1
Row Col Number Name
A 16 C01385 RADIO NAVIGATION RADIO ALTM 2
D. Related Data
(1)
(SSM 34-33-11).
(2)
(SSM 34-33-21).
(3)
(WDM 34-33-11).
(4)
(WDM 34-33-21).
E. Initial Evaluation
(1) Do
this
task:
Low
Range
Radio
Altimeter
(LRRA)
BITE
Procedure,
34-33
TASK
801.
(a)
If the red XMIT ANT FAIL light stays on, then do the Fault Isolation Procedure below.
(b)
If the red XMIT ANT FAIL light goes off, then there was an intermittent fault.
F. 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:
EFFECTIVITY
34-33 TASKS 806-807
SIL ALL
Page 214 D633A103-SIL Jun 15/2010
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)
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