What happened
On November 19, 2006, a Robinson R44 helicopter, registration PT-YSY, was performing sightseeing flights during a social event in Ibiúna, São Paulo. Shortly after takeoff, the pilot observed a drop in main rotor RPM, accompanied by the low-RPM warning light. As the aircraft began to lose altitude, the pilot attempted an emergency landing near a small lake.
During the maneuver, the pilot increased the collective and moved the cyclic backward to mitigate the descent. The aircraft's skids made contact with the edge of a bank by the lake, causing the helicopter to slide approximately three meters. The impact caused one of the main rotor blades to strike the tail boom, completely severing it near the tail rotor gearbox. Despite the severe damage to the aircraft, the pilot and the three passengers escaped without injury.
The investigation
CENIPA investigators examined the aircraft's engine and fuel system, finding significant amounts of water and solid residue in the fuel samples taken from the carburetor and fuel system. The investigation also looked into the takeoff procedures and the operational environment. While the engine passed bench tests for RPM and manifold pressure, the presence of contaminants suggested that the refueling process—conducted via canisters at an uncertified location—may have introduced impurities into the fuel.
Investigators also noted that the pilot performed a vertical takeoff, which deviated from the manufacturer's recommended height-versus-velocity charts. The investigation further revealed that the operation lacked proper regulatory authorization and that the takeoff area contained several obstacles that complicated the approach and departure gradients.
Findings
- Fuel contamination likely caused a momentary interruption in engine power during the high-demand takeoff phase.
- Improper flight planning and a lack of adherence to safety regulations regarding operations in non-certified locations.
- Poor pilot judgment regarding the selection of a landing site with significant obstacles.
- Inadequate takeoff technique, specifically performing a vertical takeoff that exceeded recommended safety limits for the aircraft's performance envelope.
- Operational informality, including refueling using canisters in an unapproved area, which contributed to the introduction of water and debris into the fuel system.