2
nd
Edition - Rev 0
SUPPLEMENT SG-1
CHAPTER 34 - NAVIGATION
Page 16
Annunciation Associated
LRU
Solution
HDG FAIL
GRS 77 &
GMU 44
• Check PFD Alert Window for PFD, MFD or
GRS configuration, software or failed data path
error messages. Correct any errors before pro-
ceeding.
• Ensure metal objects (tool boxes, power carts,
etc.) are not interfering with the magnetometer
and aircraft is not in hangar, near other build-
ings, parked over metal drainage culverts or on
hard surfaces that may contain steel reinforce-
ments
• Ensure that a cell phone or a device using cell
phone technology is not turned on (even in a
monitoring state) in the cabin.
• Cycle power after moving aircraft away from
metal objects to determine if metal objects were
the source of the interference. Allow up to five
minutes for the heading to reinitialize.
• Perform a Magnetometer Interference Test to
check for interference from onboard electrical
system components (e.g. NAV lights). Pay par-
ticular attention to any new electrical devices
that have been installed since the aircraft was
new. Correct any discrepancies that do not al-
low this test to pass before continuing.
• Ensure GRS 77 and GMU 44 connectors are se-
cure.
• Check the wiring and any inline connectors be-
tween the GRS and GMU for faults.
• Recalibrate the GMU 44.
• Replace the GMU 44.
• If problem persists, replace the GRS 77.
OAT
and
TAS
GTP 59
• Check OAT probe wiring, probe and connectors
for faults or damage.
• Replace GDC 74A config module.
• Replace the GTP 59.
• If problem remains, replace GDC 74A.
To Next Page
Loading...
