What happened
On November 11, 2005, a Robinson R22 helicopter, registration PT-YCZ, was performing a local aerial news flight over São Paulo, Brazil. The aircraft departed from Campo de Marte aerodrome carrying a pilot and one passenger. During the flight, the pilot experienced a sudden, strong yaw and noticed the engine RPM surging, followed by the activation of the engine-to-transmission engagement warning light.
In response to the loss of power, the pilot immediately initiated an autorotation procedure to perform an emergency landing on an avenue. During the descent and landing, the helicopter collided with an automobile on the Avenida das Nações Unidas. The aircraft struck the ground at a 30-degree lateral tilt and slid approximately 70 meters before coming to rest on its right side. Despite the severe damage to the aircraft, both the pilot and the passenger were uninjured, and there were no fatalities among persons on the ground.
The investigation
CENIPA investigators examined the engine and transmission components to determine the cause of the power loss. Laboratory testing conducted by the Instituto de Aeronáutica e Espaço (IAE) focused on the drive belt assembly. The investigation revealed that the front belt had slipped off its pulley, and fragments of the rear belt were also recovered from the site.
Technical analysis showed that the belts had failed due to delamination between the reinforcement fibers and the outer rubber layer, a condition caused by material fatigue. Furthermore, the belts exhibited significant wear that was inconsistent with the flight hours recorded in the maintenance logs. While the operator's records indicated that the belts had only 124 hours of use since a major overhaul, the physical condition of the components suggested much higher usage.
Findings
- The primary cause of the accident was a failure in the power transmission system due to the rupture of the drive belts.
- The installed belts were heavily worn and did not match the specific parts described in the aircraft's maintenance documentation.
- There was a lack of adequate maintenance supervision, which failed to detect discrepancies between the actual components installed and the official maintenance logs.
- The investigation could not confirm if the belts were improperly replaced with used parts or if the maintenance records were simply inaccurate, rendering the components unapproved for flight.