What happened
On 2 January 2020, an Airbus A3LL0-343, registration TC-JNI, departed Cape Town International Airport (FACT) on a scheduled commercial flight bound for Istanbul. Shortly after rotation, the flight crew attempted to retract the landing gear as part of the after-takeoff checklist. However, the gear failed to retract, triggering a landing gear retraction fault message on the cockpit's ECAM panel.
In response to the technical anomaly, the crew requested air traffic control permission to enter a holding pattern over Robben Island at 8,000 feet. During this period, the crew attempted various troubleshooting procedures, including resetting the computer and the landing gear control interface units, but the gear remained in the extended position. After approximately two hours of holding, the operator's control centers directed the aircraft to divert to O.R. Tambo International Airport (FAOR) in Johannesburg, as that facility possessed the necessary technical equipment to address the fault.
The investigation
Following the incident, the aircraft was moved to a maintenance hangar and placed on hydraulic jacks for inspection. Engineers performed extension and retraction tests, which replicated the fault reported by the flight crew.
Upon detailed measurement of the left landing gear components, investigators discovered that the in-board pitch trimmer proximity sensor was out of tolerance. The sensor measured 8.40mm, exceeding the maximum allowable limit of 8.30mm. Maintenance crews subsequently adjusted the sensor, and subsequent tests confirmed the gear was operating correctly. The aircraft was returned to service on 3 January 2020.
Findings
- The landing gear retraction failure was caused by the right-side pitch trimmer proximity sensor on the left gear being out of its specified limit.
- The sensor deviation was likely the result of wear and tear causing damage to the proximity switch sensor or target.