What happened
On a daytime VFR flight from Campbell River to a private airstardrip near McIvor Lake, British Columbia, a Robinson R-22 Beta helicopter, registration C-FHGH, experienced a sudden loss of rotor power. As the aircraft approached the lake, the engine noise increased and the RPM rose, followed by a steep descent. During the descent, the pilot experienced popping and banging noises as the helicopter's forward motion slowed and the vertical descent rate increased. The aircraft struck the water with high vertical velocity and low rotor RPM, sinking in approximately 30 feet of water. The pilot, the sole occupant, sustained fatal injuries.
The investigation
Investigators examined the wreckage and found that while the engine crankshaft was still rotating upon impact, the main rotor blades showed damage consistent with low RPM. Evidence indicated that both drive belts had "walked" off their sheaves, effectively disconnecting the engine's power from the rotor system.
Technical analysis of the drive belts revealed they were significantly shorter than the minimum allowable dimensions. While the belts were initially installed correctly following a recent overhaul, testing suggested they had shrunk in length. Further investigation into the electrical system revealed that a non-standard 10-amp fuse had been installed instead of the required 1.5-amp fuse. Additionally, the fuse holder was improperly secured with a ty-wrap and featured poor solder joints and corrosion. These electrical defects increased resistance in the circuit, which slowed the operation of the belt-tension actuator motor.
Findings
- The primary cause of the engine-rotor disconnection was the shrinkage of the V-drive belts, likely caused by excessive heat.
- This heat was generated because the electrical resistance from a corroded, non-standard fuse holder and poor solder joints slowed the actuator motor, increasing the time required for the tensioning process.
- During the final stages of the autorotation, the main rotor RPM dropped below safe limits, leaving the pilot with insufficient energy to arrest the descent.
- The use of an unauthorized "work-around" (tapping the motor to engage the clutch) masked the underlying electrical issue.
- The installation of a 10-amp fuse instead of a 1.5-amp fuse removed a critical safety defense against over-tensioning the belts.