03/15/21
Message Overview:
Message Description:
Proximity Sensor Electronic Unit detects that the left gear was in transit between Uplock and Downlock for more than 28 seconds. Verify rigging/status.
Possible Causes:
- Main Landing-Gear Uplock Proximity-Sensor (LH) (PX05)
- Main Landing-Gear Downlock 1 Proximity-Sensor (LH) (PX09)
- Main Landing-Gear Downlock 2 Proximity-Sensor (LH) (PX39)
- Landing Gear Selector Valve (V9)
- Landing Gear Control Panel (PL10)
- Proximity Sensor Electronic Unit (PSEU) (A9)
- Associated Wiring
Troubleshooting Tips:
Advisory Wire/Service Bulletin: None
Forum Articles/Infoservice/Newsletter: None
Quick Links:
| Adjustment of the Proximity Sensors | AMM 32-61-00-820-801 |
| Removal of the Main Landing-Gear (MLG) Proximity-Sensors | AMM 32-61-01-000-801 |
| Installation of the Main Landing-Gear (MLG) Proximity-Sensors | AMM 32-61-01-400-801 |
| Functional Test of the Proximity-Sensor Electronic Unit (PSEU) | AMM 32-61-09-720-801 |
| Standard Practices - Replace Wiring | SPM 20-12-00-02 |
| Standard Practices - Wire Repair | SPM 20-12-10-02 |
Troubleshooting Recommendations:
- Does the left main gear physically take more than 28 seconds to transit between the uplock and downlock positions?
- If YES, continue with next step.
- If NO, go to step 8.
- Access Junction Box 4 (JB4) in the RH avionic equipment rack. Open the front cover of JB4 to access the DB2 circuit card test points.
NOTE: Make sure to follow all electrostatic discharge safety measures. - For the following test, make sure the aircraft is weight on wheels, hydraulic power is OFF and the landing gear pins are installed.
- Perform a voltage check of the extend solenoid as follows:
Landing Gear Handle Position From To Expected Result Result Extend JB4 DB2 test point 1 JB4 DB2 test point 2 28 VDC ±4 VDC Retract JB4 DB2 test point 1 JB4 DB2 test point 2 0 VDC ±0.8 VDC - If results are as expected, continue with next step.
- If results are not correct, go to step 7.
- Remove the Landing Gear Control handle. Perform a continuity check of the landing gear selector valve extend solenoid as follows:
From To Expected Result Result JB4 DB2 test point 1 JB4 DB2 test point 2 Continuity - Is there is continuity, continue with next step.
- If there is no continuity, replace the landing gear selector valve (V9)
- Access the landing gear selector valve and disconnect connector V9P1. Perform a continuity check of the retract solenoid as follows:
From To Expected Result Result V9P1-A V9P1-B Continuity - If there is continuity, go to step 8.
- If there is no continuity, replace the landing gear selector valve.
- Perform a wiring check of the landing gear control handle on the landing gear control panel as follows:
From To Expected Result Result Extend Retract Extend Retract PL10J1-1 PL10J1-2 Continuity Open PL10J1-17 PL10J1-3 Open Continuity PL10J1-17 PL10J1-4 Continuity Open PL10J1-6 PL10J1-5 Open Continuity PL10J1-18 PL10J1-11 Continuity Open - If results are not correct, replace the landing gear control handle or panel and do close out.
- If results are correct, continue with next step.
- Perform rigging and adjustment of proximity sensor PX09. Is the fault still present?
- If YES, continue with next step.
- If NO, do close out.
- Replace proximity sensor PX09. Is the fault still present?
- If YES, continue with next step.
- If NO, do close out.
- Perform rigging and adjustment of proximity sensor PX39. Is the fault still present?
- If YES, continue with next step.
- If NO, do close out.
- Replace proximity sensor PX39. Is the fault still present?
- If YES, continue with next step.
- If NO, do close out.
- Perform rigging and adjustment of proximity sensor PX05. Is the fault still present?
- If YES, continue with next step.
- If NO, do close out.
- Replace proximity sensor PX05. Is the fault still present?
- If YES, continue with next step.
- If NO, do close out.
- Replace the PSEU.
- Do close out.