TM 1-1520-238-T-5
8–170
8–91.
FLIGHT INSTRUMENTS – MAINTENANCE OPERATIONAL CHECK (cont)
8–91
Task
Result
o. On pilot forward circuit breaker panel
(fig. 8–46), check that VDU circuit breaker is
closed.
If circuit breaker does not stay closed, troubleshoot
VDU electrical system (TM 11-1520-238-23-2).
If the internal vibrator in the pilot barometric altimeter
is not heard, go to paragraph 8–103.
If the internal vibrator in the CPG barometric altimeter
is not heard, go to paragraph 8–104.
p. Compare pilot barometric altimeter
(fig. 8–48) reading to test site ambient
barometric pressure (reading obtained from
control tower).
If barometric altimeter pressure reading is not within
70 feet of ambient pressure, check the barometric
altimeter (TM 1-1500-204-23) and replace pilot
barometric altimeter (TM 1-1520-238-23) if tolerances
are exceeded.
q. Compare CPG barometric altimeter
(fig. 8–45) reading to test site ambient
barometric pressure reading.
If barometric altimeter pressure reading is not within
70 feet of ambient pressure, check the barometric
altimeter (TM 1-1500-204-23) and replace CPG
barometric altimeter (TM 1-1520-238-23) if tolerances
are exceeded.
r. Perform Pitot and static port system, line,
leak check (TM 1-1500-204-23).
Replace any component(s) that failed leak check
(TM 1-1520-238-23).
3. Turn INST control on CPG INTR LT panel (fig. 8–44) to OFF.
4. Turn INST control on pilot EXT LT/INTR LT panel (fig. 8–47) to OFF.
5. On pilot ELEC PWR panel (fig. 8–42), set BATT/EXT PWR switch to OFF.
6. Remove external power – electrical (TM 1-1520-238-23).
7. Remove Pitot and static system tester (TM 1-1520-238-23).
8. Disconnect maintenance headset (TM 1-1520-238-T-4).
END OF TASK
