KBSZ Investigation of Wizz Air A320 Main Landing Gear Door Incident (HA-LWA)

Event Overview and Investigation Scope On December 3, 2013, at 01:31 UTC, a Wizz Air Airbus A320 (registration HA-LWA) experienced a maintenance incident at Warsaw (WAVV/EPVVA), Poland. During a scheduled eight-day inspection of the main landing gear door, the right-side door opened approximately 20 cm from its closed position and became jammed. The mechanic attempted to move the door manually, heard a metallic sound, and the door subsequently opened. The Hungarian Transport Safety Authority (KBSZ) initiated the investigation under applicable aviation safety laws, while the Polish SCAAI stated it would not conduct a separate investigation. ## Technical Examination and Findings The aircraft was already equipped with a modified actuator (P/N: 114122014) following a previous incident involving a different Wizz Air A320 (HA-LWM) in June 2013. The French BEA provided X-ray images of the jammed actuator, which showed no visible damage to the piston spacer, damping ring, or locking ring. On January 16, 2014, GE Aviation System Ltd. experts, alongside KBSZ and BEA representatives, tested the actuator. Hydraulic pressure tests showed the piston moved at 17.5 psi for opening and 25 psi for closing, while manual extraction required 64 lbf, dropping to 60 lbf after movement. Upon disassembly, the actuator housing and piston seals showed no abnormal wear or damage. However, corrosion was found on all three components of both the A and B units of the pressure-reducing unit (restrictor). The actuator was reassembled and tested on an Airbus A320 landing gear test stand in Filton, where it operated correctly through multiple cycles. ## Conclusions and Safety Actions KBSZ concluded that the piston, seals, and housing were undamaged and could not have caused the jam. The agency determined that the incident was likely caused by a possible jam of the pressure-regulating unit's moving parts due to corrosion. The exact timing of the corrosion—whether during previous operation, storage after the service bulletin, or subsequent operation on HA-LWA—could not be determined. Hydraulic fluid analysis showed chemical composition within Airbus maintenance manual limits. Following the event, Airbus modified the Flight Crew Operating Manual on June 2, 2014, to require up to five full landing gear recycling attempts if a GEAR NOT DOWNLOCKED warning occurs. KBSZ did not issue a safety recommendation and closed the investigation on November 8, 2015.