What happened
On February 10, 2010, an AS350 BA helicopter, registration PT-YRE, was conducting an aerial footage operation near São Paulo, Brazil. Approximately 30 minutes into the flight, the pilot experienced significant difficulties with the aircraft's directional control. The pilot contacted São Paulo Approach Control to report tail rotor problems and declared an emergency, stating an intention to perform an emergency landing at the Jockey Club.
During the final moments of the flight, the pilot communicated to other aircraft in the vicinity that applying left pedal caused intense vibrations. Shortly after these transmissions, the aircraft entered a descending spiral and crashed into the ground at the Jockey Club. The accident resulted in one fatality (the pilot) and one serious injury (the passenger).
The investigation
CENIPA's investigation focused on the mechanical integrity of the tail rotor system and the maintenance practices of the operator. Investigators examined the wreckage and found that the tail rotor fork may have been incorrectly installed in the conical shaft, either with the tongue outside the groove or due to insufficient torque on the fastening bolt. This error allowed the fork to rotate relative to the shaft.
The investigation also scrutinized the maintenance records, noting that while the aircraft had a valid airworthiness certificate, several intermediate inspections were overdue. The investigation found that the operator frequently deferred these inspections until the 100-hour interval. Furthermore, there were no records of daily preflight or post-flight inspections, nor records of required engine compressor washings.
Findings
- Mechanical failure: The primary cause was a system or component failure involving the tail rotor assembly, specifically the improper installation of the fork in the conical shaft.
- Maintenance oversight: The lack of up-toed intermediate inspections prevented the detection of the assembly error.
- Organizational culture: The operator's work organization was unsystematized, characterized by informal procedures, a lack of technical oversight by supervisors, and a lack of qualified support personnel to perform daily inspections.
- Maintenance management: The maintenance workshop lacked sufficient monitoring of critical assembly phases, as the inspector was not present during the application of torque on the fork fastening bolt.