What happened
On 16 January 2016, a SOCATA TB-20, registration EC-ESK, was performing a visual flight from Mutxamel aerodrome to Pajares de los Oteros aerodrome when it encountered a large bird in the Serranía de Cuenca Natural Park. While cruising at approximately 6,400 feet, the aircraft struck an adult griffon vulture on the leading edge of the left wing.
The impact was severe enough to cause a portion of the left wing to detach from the airframe. This structural failure led to an immediate loss of control. The aircraft entered a dive and crashed into a wooded area seconds later. The impact with the terrain and trees resulted in the destruction of the aircraft and the death of all four occupants (one pilot and three passengers).
The investigation
The CIAIAC investigation focused on the mechanics of the bird strike and the structural integrity of the aircraft. Investigators analyzed the kinetic energy of the impact, noting that the vulture, weighing between 6 and 9 kg, delivered between 15,561 and 23,342 joules of energy.
Evidence from the wreckage showed that debris from the left wing, including the aileron and wingtip, was found approximately one kilometer away from the main impact site, alongside the remains of the bird. The investigation also reviewed the aircraft's certification, noting that under the applicable FAR-23/CS-23 standards for the normal category, the aircraft was not required to withstand impacts from birds of this mass.
Findings
- The accident occurred in an area identified in the Aeronautical Information Publication (AIP) as a primary breeding ground for vultures.
- The loss of control following the loss of part of the left wing was the primary cause of the accident.
- The kinetic energy of the vulture strike far exceeded the certification requirements for aircraft in the normal category, which only mandate resistance to much smaller birds.
- The pilot's visibility may have been compromised by the sun's position near the flight path's line of sight, potentially preventing an effective evasive maneuver.