TM 55-1520-240-T
CHAPTER 18
INSTALLED AVIONIC SYSTEMS TROUBLESHOOTING
CHAPTER OVERVIEW
Chapter 18 contains procedures for Installed Avionic Systems troubleshooting. Each
avionic system and failure symptom is listed below. Included in this chapter are locations
and views of all electrical connectors, receptacles, relays, and ground connections for
each Installed Avionic System.
Refer to TM 55-1520-240-23 for required Avionic System maintenance procedures.
SYSTEM
PARA
GLOBAL POSITIONING
18-1
ALTITUDE VOICE WARNING SYSTEM
18-2
(RADAR ALTIMETER
DOPPLER/GPS NAVIGATION SYSTEM (DGNS
18-3
HF LIAISON FACILITY
18-4
FAILURE SYMPTOM LIST
GLOBAL POSITIONING SYSTEM
S Y M P T O M
TASK
S Y M P T O M
TASK
GPS DISPLAY DOES NOT TURN ON OR VARY
18-1.4
GPS SYSTEM TRACKS LESS THAN FOUR
18-1.7
WITH CDU BRT CONTROL
SATELLITES AND ESTIMATED POSITION ERROR
(EPE) IS NOT WITHIN LIMITS OF THE SYSTEMS
FIGURE OF MERIT (FM)
NO MOVEMENT OF GPS RCVR TIME
TOTALIZING METER
GPS CDU DISPLAYS “FAIL” MESSAGE
18-1.5
18-1.6
DATA LOADER MODULE INFORMATION DOES NOT
LOAD INTO GPS SYSTEM BUT NO ERROR
MESSAGE APPEARS ON CDU
18-1.8
KYK-13 KEY LOADING DISCREPANCIES
18-1.9
S Y M P T O M
GPS ALERT INDICATOR DISCREPANCIES
T A S K
18-1.10
PILOT/COPILOT HSI DISCREPANCIES
18-1.11
GPS SYSTEM WILL NOT ZEROIZE
18-1.12
GPS SYSTEM WILL NOT RETAIN LOADED
DATA AFTER AIRCRAFT POWER IS
18-1.13
REMOVED
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Change 21 18-3
