What happened
On September 26, 2004, a Robinson R-44 helicopter, registration PT-YAI, was conducting a specialized flight operation over the city of Populina, São Paulo. The mission involved flying at a low altitude to disperse shredded paper over the urban area. Approximately five minutes after departing from a nearby farm, the aircraft experienced a sudden loss of engine power.
As the aircraft lost altitude, it struck a public lighting pole and the roof of a service station before ultimately impacting the ground. Despite the severe damage sustained by the aircraft, the pilot and two passengers escaped the crash without injuries.
The investigation
CENIPA investigators examined the engine and air intake systems to determine the cause of the power loss. While fuel quality and quantity were found to be normal, investigators discovered a significant amount of shredded paper lodged within the engine's air intake, including the filter, intake tract, and even inside cylinder number four.
The investigation also revealed that the aircraft's airworthiness certificate had been suspended since May 2004, and several required maintenance inspections—including the 25, 5 and 100-hour intervals—had been bypassed, with the aircraft having completed approximately 46 flights with overdue inspections. Furthermore, the flight was being conducted from an unapproved site that lacked minimum safety requirements, and the pilot was not authorized for this specific type of operation.
Findings
- The primary cause of the engine failure was the obstruction of the engine air intake by shredded paper, which prevented sufficient airflow to the engine.
- The pilot's lack of experience with the R-44 model contributed to a lack of awareness regarding the vulnerability of the lateral air intake to debris.
- Poor flight planning and judgment were evident, as the pilot operated at an altitude too low to safely execute an autorotation procedure following the power loss.
- Operational indiscipline was noted, as the flight was conducted with a suspended airworthiness certificate and without authorization for the specific mission type.