What happened
On June 4, 2001, a PIPER PA-36-300, registration EC-GXH, was conducting functional tests at the Robledillo de Mohernando aerodrome in Guadalajara. The pilot intended to perform several ground runs, consisting of accelerating and braking the aircraft without taking flight, to verify engine parameters and flight control functionality.
During the first run, the pilot noted a tendency for the aircraft to veer to the left and suspected a potential hydraulic leak in the left brake pedal, as the brake required multiple applications to engage effectively. During the second run, the pilot attempted to reduce speed by applying both brakes. At this moment, the aircraft veered to the right and exited the runway. As the aircraft traveled across the runway strip, the left main landing gear leg fractured, causing the aircraft to come to a stop. The pilot sustained one injury (minor/none reported for crew, but the report notes the pilot's experience and the event).
The investigation
The investigation focused on the structural failure of the landing gear and the loss of directional control. Inspectors examined the junction where the left landing gear leg meets the wing structure, discovering significant corrosion on both the leg and the surrounding airframe.
Additionally, an inspection of the cockpit revealed that the control column locking device—used to secure the elevator and ailerons while parked—had not been removed. This triangular metal plate was found partially broken, likely due to the pilot's attempt to disengage it during the second run.
Findings
- The pilot failed to verify the freedom of the flight controls before taxiing or during the initial ground run, leaving the control column lock engaged.
- The loss of directional control was directly caused by the inability to use the control column due to the unremoved locking mechanism.
- The failure of the left main landing gear leg was caused by the combined effects of structural corrosion and the mechanical loads imposed by irregularities in the runway strip during the excursion.