Maintenance Manual
190-02472-02
G3X Touch EFIS Part 23 AML STC
Revision 2
Page 30
Table 4-2 – Electrical Bonding Procedure
Unit
Measurement Location (3)
Result
(milliohm)
GDU 4X0 (PFD)
J4X02 backshell to ground stud
(2)
m
Ω
GDU 4X0 (MFD) (if
installed)
J4X02 backshell to ground stud
(2)
m
Ω
GSU 25D
(1)
Chassis mounting screw to adjacent aircraft ground
m
Ω
P251 backshell to ground stud
(2)
GMU 11
P111 backshell to ground stud
(2)
m
Ω
GAD 29B
Chassis mounting screw to adjacent aircraft ground
m
Ω
GAD 27
Chassis mounting screw to adjacent aircraft ground
m
Ω
GEA 24
Chassis mounting screw to adjacent aircraft ground
m
Ω
GDL 5XR
P5X1 backshell to ground stud
(2)
m
Ω
Notes:
(1) For remote mounted – it is bonded via the c
hassis mounting
to aircraft ground.
For GDU-mounted – it is bonded via bonding strap to a ground stud
(2) This is the ground stud that the LRU bonding strap is connected to.
(3) For remote LRUs bonded to the back of the instrument panel via an installed aluminum foil ground plane,
the bonding measurement must be taken between the remote LRU and the instrument panel.
4.6 GSU 25D Earth Magnetic Field Updates
The GSU 25D utilizes an Earth magnetic field model which is updated once every five years. The IGRF
(International Geomagnetic Reference Field) update is expected to be available from Garmin in July 2020
and every five years thereafter, as long as the GSU 25D remains a Garmin-supported product.
The IGRF model is automatically updated with a GDU software update. The G3X system alerts the
operator the magnetic field database is out of date by issuing the message “AHRS SERVICE – AHRS
Magnetic-field model needs update”. Garmin will distribute update instructions when updates are
available.
4.7 Special Inspection Requirements
After a suspected lighting strike, the following actions must be performed for the specific LRU.
GTP 59 Temperature Probe
Inspect the GTP 59 temperature probe for signs of lightning damage. Check the self-sealing washer (P/N
212-00026-00) used on the probe tip outside of the aircraft for any evidence of melting or lack of seal.
Replace the washer if damaged. If there is evidence of lightning strike to the GTP 59 temperature probe
or any lightning damage, replace the probe.
Tube-and-fabric aircraft must replace the GTP 59 bond strap (if installed) in accordance with Section 4 of
the
G3X Touch EFIS Part 23 AML STC Installation Manual
(190-02472-01).
G3X Equipment
All G3X equipment should be checked per Section
7
. If equipment is not functioning correctly,
troubleshoot using information in Section 5. Contact Garmin Product Support before replacing G3X LRUs
to verify all troubleshooting options were exhausted.
