Incident Overview
On June 4, 2001, at approximately 12:30 local time, a Piper PA-36-300 with registration EC-GXH experienced an accident during ground operations at the Robledillo de Mohernando aerodrome in Guadalajara. The single-engine aircraft was powered by a Lycoming IO-540-K1G5 engine. The pilot, a 34-year-old commercial pilot with 3,700 total flight hours and 900 hours on type, was conducting functional tests of the engine and flight controls.
Sequence of Events
The pilot initiated several ground runs to verify system performance without taking off. During the first run, the aircraft exhibited a tendency to drift left, and the pilot suspected a potential issue with the left brake pedal. During the second run, similar handling characteristics were observed. When the pilot attempted to reduce speed by applying both brakes, the aircraft veered sharply to the right and departed the runway surface.
The aircraft continued rolling on the adjacent strip until it came to a stop. The pilot shut down the engine and secured the propeller immediately after leaving the runway. During this final phase of movement, the left main landing gear strut fractured, resulting in damage to the gear and the propeller. No injuries were reported to the pilot or any other persons.
Investigation Findings
Post-accident inspection revealed significant corrosion on the left main gear strut and its attachment points to the wing structure. Additionally, investigators found that the control lock mechanism for the elevator and ailerons was still engaged. This triangular locking device, designed to prevent wind-induced movement of the controls while parked, had been partially broken, likely by the pilot attempting to release it during the final run.
Probable Cause Analysis
The investigation concluded that the loss of control occurred because the pilot failed to remove the control lock before taxiing. This prevented the use of the elevator and ailerons, making it impossible to maintain directional stability. The subsequent fracture of the left main gear was attributed to two factors: loads generated by irregularities in the runway strip surface and the reduced structural integrity of the strut due to severe corrosion.