SUPPLEMENT SG-3
CHAPTER 31 - INDICATIONG SYSTEM
AHRS1 GPS – AHRS 1
not receiving backup GPS
information.
AHRS is not receiving GPS
information from GPS2.
Ensure that a cell phone or
a device using cell phone
technology is not turned on
(even in a monitoring state)
in the cabin.
Check GPS status. If one or
both GPS receivers cannot
acquire a position lock,
troubleshoot GPS problems
using Replace the GRS 77.
AHRS magnetic field mod-
el should be updated. Ap-
pears on ground only.
Update GRS 77 IGRF
model (current model is
with aviation database).
AHRS is not
receiving true
airspeed from
ADC.
GDC not powered up.
Close ADC C/B.
GDC not receiving input
from GTP 59 OAT probe.
Verify wiring is correct.
ARINC 429 connection
from GDC 74A to GRS 77
is not working. Verify wir-
ing is correct.
The configuration module
is inoperative.
Verify wiring to configura-
tion module
Replace configuration
module
Pilot stored data was lost.
Recheck data and settings.
Fan 1 has reported 0 RPM
when it was powered with a
PWM duty cycle higher
than or equal to 10%
This error appears whenev-
er the GDU is replaced
with a GDU that was con-
figured for a different in-
stallation.
Cycle power to the GDU.
This error automatically
clears on the second power
up with a different configu-
ration module.
Error in the configuration
of the GDU 620.
Specific GDU has poor
cooling, and power usage is
being reduced.
Ensure fans on indicated
GDU are functioning
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