What happened
On 29 September 2011, a Beechcraft D35, registration PT-AVK, departed from Santarém Aerodrome (SBSN) for a local flight. Shortly after takeoff, air traffic controllers lost radio contact with the aircraft. The approach controller eventually re-established communication with the pilot via a mobile phone, at which point the pilot reported radio equipment malfunctions. The controller provided instructions for the aircraft to return to the airport. Approximately 45 minutes later, the controller received notification that the aircraft had crashed in the Comunidade de Lavras region. The impact, which occurred in a pitch-down attitude of approximately 90 degrees, resulted in two fatalities (the pilot and one passenger) and the complete destruction of the aircraft.
The investigation
CENIPA investigators examined the wreckage distribution, which showed a linear pattern. The stabilizers and ruddervators were located approximately 800 meters upstream from the main wreckage concentration. Physical testing revealed that the left stabilizer had detached from the tail cone due to a fracture at the front fixation point. The investigation identified that the fracture was caused by structural weakening from accentuated corrosion and the failure to install a required stabilizer root reinforcement kit. Furthermore, investigators found that the aircraft's maintenance records were incomplete, and the workshop could not provide evidence of compliance with Airworthiness Directive AD 94-20-04R2, which is intended to prevent structural failure of the V-tail.
Findings
- Inflight loss of component: The left stabilizer detached due to an overload on a weakened fixation point.
- Corrosion: Significant corrosion was present at the front fixation point of the stabilizer.
- Maintenance non-compliance: The mandatory service bulletin MSB 2188, which prescribes a stabilizer root reinforcement kit, had not been implemented.
- Failure to follow AD: The aircraft was not in compliance with AD 94-20-04R2, which requires specific inspections for corrosion in load-bearing surfaces.
- Managerial oversight: A failure in the maintenance management process allowed the lack of compliance with the mandatory service bulletin and the airworthiness directive to go undetected during the last inspection.