NLG Downlock Proximity Sensor Fault

TASK 32-31-00-810-824-A
NLG Downlock Proximity Sensor Fault

WARNING: MAKE SURE THAT THE GROUND SAFETY-LOCKS ARE IN POSITION ON THE LANDING GEAR. MOVEMENT OF THE LANDING GEAR CAN CAUSE INJURY TO PERSONS AND DAMAGE TO THE AIRCRAFT AND/OR EQUIPMENT.

WARNING: PUT THE SAFETY DEVICES AND THE WARNING NOTICES IN POSITION BEFORE YOU START A TASK ON OR NEAR:

THE FLIGHT CONTROLS
THE FLIGHT CONTROL SURFACES
THE LANDING GEAR AND THE RELATED DOORS
COMPONENTS THAT MOVE.

MOVEMENT OF COMPONENTS CAN KILL OR CAUSE INJURY TO PERSONS AND/OR CAN CAUSE DAMAGE TO THE EQUIPMENT.

1. Possible Causes

PROX SNSR-NLG DNLK, SYS 1 [18GA]
PROX SNSR-NLG DNLK, SYS 2 [19GA]
wiring
LGCIU-1 [5GA1]
LGCIU-2 [5GA2]

2. Job Set-up Information
A. Fixtures, Tools, Test and Support Equipment

REFERENCE	QTY	DESIGNATION
No specific	1	INDUCTANCE METER 1KHZ
No specific	AR	MULTIMETER - STANDARD
No specific	AR	TESTER - INSULATION RESISTANCE
38-368-02	1	UNIT-TEST,SENSOR
38-368-03	1	UNIT-TEST,SENSOR

B. Referenced Information

REFERENCE	DESIGNATION
AMM 32-31-00-040-003	Check of the System 2 Proximity Sensors of the Landing Gear and the Landing Gear Doors
ASM 323103
ASM 323104
AMM 32-31-71-000-001	Removal of the LGCIU
AMM 32-31-71-400-001	Installation of the LGCIU
AMM 32-31-73-000-005	Removal of the NLG Proximity-Sensors
AMM 32-31-73-200-002	Inspection of the NLG Proximity Sensor and Target Clearances
AMM 32-31-73-400-005	Installation of the NLG Proximity-Sensors
AMM 32-31-73-820-008	Inductance Check of the Proximity Sensors/Switches
AMM 32-69-00-740-001	BITE Check of Landing-Gear Control Interface-Unit (LGCIU) With Use of MCDU to Ensure that Continuous BITE is Operative
TSM TASK 32-31-00-03	NORMAL EXTENSION AND RETRACTION - TASK SUPPORTING DATA

3. Fault Confirmation
Subtask 32-31-00-740-064-A

A. Test
(1) Do a BITE test of the applicable LGCIU 1 or LGCIU 2, which identified the NLG proximity-sensor fault AMM 32-69-00-740-001:

if a N L/G DNLK PROX SNSR message is shown, do the fault isolation procedure in Para. 4.A.(2).

(2) If a L/G DNLK PROX SNSR message is shown on the Post Flight Report (PFR), do the fault isolation procedure in Para 4.A.(1).

NOTE: The N L/G DNLK PROX SNSR TGT POS fault cannot be identified by the BITE test. The BITE test can only confirm an open-circuit or short-circuit in the proximity-sensor or its related wiring. Target position faults can only be confirmed by continuous BITE during L/G operation. To confirm a target position fault, it is necessary to do the proximity-sensor/target inspection and the inductance check, given in the fault isolation procedure.

4. Fault Isolation
Subtask 32-31-00-810-075-A

A. Procedure
(1) If the PFR shows a proximity sensor target-position fault, do the steps follow:
(a) Do the inspection of the PROX SNSR-NLG DNLK, SYS 1 [18GA] and the PROX SNSR-NLG DNLK, SYS 2 [19GA] AMM 32-31-73-200-002.
(b) Use the INDUCTANCE METER 1KHZ to do a check of the inductance of the applicable proximity sensor AMM 32-31-73-820-008:

If the fault continues, do step (2).

(2) If the BITE test shows a proximity sensor fault, do the steps that follow:
(a) At the applicable proximity sensor, release the electrical-connector.
(b) If the 38-368-02 UNIT-TEST,SENSOR or the 38-368-03 UNIT-TEST,SENSOR is available, do the troubleshooting procedure of the proximity sensor 32-31-00-03 TSM TASK 32-31-00-03.
(c) Use the MULTIMETER - STANDARD and do a check of the resistance between pins A and B of the applicable proximity sensor ASM 323103 or ASM 323104. Make sure that the resistance is:

Between 11 and 13 ohms for a ferrite proximity sensor (PN 8-484-01)
Between 15 and 17 ohms for an all metal proximity sensor (PN 8-933-01).

(d) Connect pins A and B together.
(e) Connect one test lead of a TESTER - INSULATION RESISTANCE to pins AB and the other test lead to the case.
(f) Supply a test signal for five seconds and read the resistance value shown.
(g) Make sure that the resistance is more than 400 Megohms.
(h) From the resistance checks in steps (c) and (g):

If the two resistance values are correct, do step (4)
If one or more of the resistance values is not correct, do step (3).

(3) Replace the PROX SNSR-NLG DNLK, SYS 1 [18GA] or the PROX SNSR-NLG DNLK, SYS 2 [19GA] AMM 32-31-73-000-005 and AMM 32-31-73-400-005.

If the fault continues, do step (4).

(4) Do a check of the wiring between the applicable proximity sensor electrical-connector and the related LGCIU ARINC tray ASM 323103 or ASM 323104.
(5) Do the test in Para. 3.A. (1).

If the fault continues, do step (6).

(6) Replace the applicable LGCIU-1 [5GA1] or the LGCIU-2 [5GA2] AMM 32-31-71-000-001 and AMM 32-31-71-400-001.
(7) If MMEL conditions apply to the PROX SNSR-NLG DNLK, SYS 2 [19GA] :
(a) Do the deactivation procedure of the proximity sensor AMM 32-31-00-040-003.

[Rev.8 from Aug 2018] 2026.04.04 04:31:20 UTC