What happened
On June 10, 2017, a Piper PA-28-151, registration EC-HPN, was conducting a dual instruction flight from Cuatro Vientos when the crew experienced a sudden, uncommanded left bank of 40–50 degrees. The instructor noted significant resistance in the flight controls, leading the crew to believe the aircraft was suffering an aileron control failure.
To manage the perceived emergency, the crew diverted to the Casarrable de Monte aerodrome. During the approach, the crew reported a second issue involving an erroneous vertical speed indicator reading. Upon landing on runway 08, the crew experienced a third perceived failure when the brakes reportedly locked. Due to the high-stress situation and the late touchdown point, the aircraft lacked sufficient remaining runway to stop, resulting in the aircraft exiting the runway and descending a steep embankment. The two occupants, an instructor and a student pilot, were uninjured.
The investigation
The CIAIAC investigation focused on the technical integrity of the flight controls, the vertical speed indicator, and the braking system. Physical inspections of the Piper PA-28-151 revealed no mechanical defects in the aileron, elevator, or rudder control systems. The cables, pulleys, and stops were all found to be in proper working order. Furthermore, the investigation found no evidence of a brake lock; instead, tire wear patterns and runway marks suggested the aircraft simply lacked sufficient distance to decelerate.
The investigation also examined the possibility of environmental factors. The investigators noted that the aircraft's flight path, altitude, and the prevailing high temperatures were highly consistent with the presence of strong turbulence, which could explain both the sudden banking and the perceived control resistance.
Findings
- The primary cause of the runway excursion was a late touchdown that left insufficient runway remaining for braking.
- A significant contributing factor was the crew's high level of stress resulting from their belief that they were operating an aircraft with failed flight controls.
- The perceived control failure and instrument discrepancies were likely caused by strong turbulence or sudden changes in air density rather than mechanical failure.
- The landing was performed on the opposite runway of the standard service direction, potentially contributing to a tailwind component.