What happened
On May 21, 2013, a Piper PA 28RT-201T, registration EC-KQL, operated by FLYBAI, was performing a local visual flight at Bilbao Airport to renew its airworthiness certificate. The flight crew included the pilot and an AESA inspector.
During the approach for landing, the pilot noticed that the green indicator light for the right main landing gear had not illuminated, indicating the gear was not confirmed as down and locked. The pilot requested a fly-by of the runway to allow ground personnel and the tower to visually verify the gear position. Although ground observers and the tower suggested the gear appeared to be down, the pilot noted that the cockpit lights only showed two green indicators (nose and left main gear).
Upon touchdown on runway 28, the right main landing gear failed to remain locked and collapsed. The aircraft's right wingtip struck the runway, causing the aircraft to skid along the pavement until it came to a halt. The two occupants exited the aircraft uninjured.
The investigation
The investigation focused on the electrical and mechanical state of the landing gear system. Post-accident testing on jacks revealed that while the hydraulic pump and the emergency extension mechanism were functional, the gear extension sequence was inconsistent. Specifically, the right gear was often the last to lock, or failed to lock entirely under certain conditions.
Electrical continuity tests identified two critical faults: the wire for the left gear (G2A) had a poor connection, and the wire for the right gear (G2C) was severed. This severed wire prevented the system from receiving the signal that the right gear had reached its down-lock position, causing the hydraulic pump to stop prematurely. The investigation also noted that the aircraft had been parked outdoors at Bilbao Airport for over ten months, exposing it to a corrosive maritime environment.
Findings
- The primary cause of the accident was the pilot's failure to execute the emergency landing gear extension procedure despite the lack of confirmation that the gear was down and locked.
- A severed electrical wire (G2C) prevented the right main landing gear from fully extending and locking.
- The pilot's decision-making was influenced by an excess of confidence and visual confirmation from ground personnel, leading him to bypass safety checks such as swapping indicator bulbs or performing an emergency extension.
- The pilot performed the landing at a higher speed than necessary by not extending the flaps, which increased the impact force on the unsecure gear.
- The operator's emergency checklists were not properly adapted to the specific aircraft systems, referencing non-existent positions like "override engage."