Loss of the ADIRU 1 Bus Input on the ISIS Indicator with the ATT HDG Selector Switch at NORM

TASK 34-22-00-810-809-A
Loss of the ADIRU 1 Bus Input on the ISIS Indicator with the ATT HDG Selector Switch at NORM

1. Possible Causes

wiring of the ADIRU 1 BUS 2 IR from the ISIS indicator (22FN) to the ADIRU 1 (1FP1)
IND-ISIS [22FN]
ADIRU-1 [1FP1]

2. Job Set-up Information
A. Referenced Information

REFERENCE	DESIGNATION
AMM 34-12-34-000-001	Removal of the ADIRU
AMM 34-12-34-400-001	Installation of the ADIRU
AMM 34-14-00-740-001	Interface Test of the IR
ASM 342202
AMM 34-22-25-000-001	Removal of the ISIS Indicator
AMM 34-22-25-400-001	Installation of the ISIS Indicator

3. Fault Confirmation
Subtask 34-22-00-700-055-A ** ON A/C NOT FOR ALL

A. Test
Not applicable, you cannot confirm this fault on the ground.

4. Fault Isolation
Subtask 34-22-00-810-061-A ** ON A/C NOT FOR ALL

A. If the fault symptom is identified by the maintenance message on the face of the ISIS indicator:
ADIRU1(1FP1) BUS IR/ISIS(22FN-10FC)
and by the red flag on the face of the ISIS indicator:
HDG

do the interface test of the IR (system 1) AMM 34-14-00-740-001.

(1) If the test gives a maintenance message, do the trouble shooting procedure related to the maintenance message.
(2) If the test is OK:

do a check of the wiring of the ADIRU 1 BUS 2 IR from the ISIS indicator (22FN) to the ADIRU 1 (1FP1) ASM 342202.

(a) If there is no continuity:

replace the defective wiring.

(b) If there is continuity:

replace the IND-ISIS [22FN] AMM 34-22-25-000-001 AMM 34-22-25-400-001.

1 After the subsequent flight, if the fault continues:

replace the ADIRU-1 [1FP1] AMM 34-12-34-000-001 AMM 34-12-34-400-001.

[Rev.8 from Aug 2018] 2026.04.04 04:32:56 UTC