Incident Overview
On January 13, 2018, at 15:00 LMT, a Robinson R44 II helicopter was conducting a training flight for the Light Helicopter Pilot License (LAPL(H)) at EPBA Bielsko Biala. During the execution of exercise I1/6 (straight flight), while in a hover, the crew heard a loud snapping sound.
Post-Event Inspection
After landing, the instructor pilot performed an engine test in accordance with Chapter 4 of the Flight Manual. The test revealed abnormal operation of the freewheel clutch, indicated by a lack of divergence between the engine and main rotor tachometer needles. The event was recorded in the helicopter's technical log, and the instructor notified the Continuing Airworthiness Management Organisation (CAMO) and the Approved Maintenance Organisation (AMO).
Mechanical Findings
The helicopter was removed from service. During inspection, a mechanic found that the clutch pulley did not rotate freely, indicating damage and blockage of the clutch assembly. The faulty component, part number C018-2 (freewheel clutch assembly), was replaced. Following replacement, a ground run was performed with satisfactory results, and the helicopter was returned to service.
Cause Determination
The investigation was conducted by the operator. The cause of the damage to component P/N:C018-2 was not determined. The Polish State Commission on Aircraft Accident Investigation (PKBWL) did not issue any safety recommendations.