What happened
On December 3, 2013, during a routine 8-day interval inspection at Warsaw Airport, maintenance personnel performing checks on the main landing gear door actuators of an Airbus A320, registration HA-LWA, encountered a malfunction. During the procedure, the right-side main landing gear door opened approximately 20 cm from its closed position and then became jammed. When a technician attempted to manually move the door downward with physical force, a metallic sound was heard, and the door subsequently opened.
This incident occurred following a serious accident on June 8, 2013, involving another Airbus A320, registration HA-LWM. In that instance, the left main landing gear failed to extend during approach to Rome Ciampino, forcing an emergency landing at Rome Fiumicino. That landing resulted in the aircraft contacting the ground on its nose and right main gear before sliding on the left main gear.
The investigation
The Hungarian Transportation Safety Bureau (KBSZ) conducted an investigation to determine if the upgraded actuator installed on HA-LWA—which had been modified per Service Bulletin to address previous failures—was susceptible to similar issues. The investigation included X-ray analysis of the actuator provided by the French BEA, and a physical examination of the component by GE Aviation System Ltd. specialists in the presence of KBSZ and BEA representatives.
Testing focused on the piston, seals, and internal housing. While the piston, damping ring, and locking ring showed no signs of damage or wear, investigators found traces of corrosion on the components within the pressure reducing unit (restrictor) of the actuator. Functional tests under hydraulic pressure demonstrated that the actuator operated correctly during laboratory testing, and subsequent operational tests on an Airbus A320 landing gear test rig at the Airbus Filton facility showed the gear doors functioned within specified time intervals.
Findings
- The internal surfaces of the actuator piston, seals, and housing were in good condition and were not the cause of the jam.
- Corrosion on the moving parts of the pressure regulator (restrictor) unit was identified as the likely cause of the malfunction.
- It could not be determined whether this corrosion developed prior to the installation of the modified part, during storage/preservation, or during the operational service of HA-LWA.
- Hydraulic fluid analysis showed no chemical deviations from the approved Airbus maintenance manual standards.
Safety action
Following these events, Airbus issued an Operational Engineering Bulletin (OEB) to modify the Flight Crew Operating Manual (FCOM) for A318/A319/A320/A321 aircraft. The new procedure instructs flight crews to perform up to five full landing gear recycling attempts if a 'L/G GEAR NOT DOWNLOCKED' ECAM warning occurs, as this may help flush debris or clear hydraulic blockages within the actuator.