Introduction
On 29 December 2019, a Robinson R44 helicopter was involved in an accident at Wijnendale, Torhout, Belgium. The Air Accident Investigation Unit of Belgium (AAIU(Be)) conducted a safety investigation and published a final report.
Factual Information
The report details the history of the flight, including the flown route and final descent. The pilot provided a report. Injuries to persons, damage to the aircraft, and other damage were documented. Personnel information, including pilot data and flying experience, was reviewed. Aircraft information covered general characteristics of the Robinson R44, relevant systems, and specific details of the accident helicopter. Meteorological conditions, aids to navigation, communications, and aerodrome information were examined. Flight recorders, wreckage and impact information, and medical and pathological information were considered. Tests and research included tests of the dual tachometers and the right magneto and engine tachometer signal.
Analysis
The analysis addressed the technical condition of the helicopter, including the engine throttle control, low rotor RPM warning system, engine and V-belt drive system. It examined the low rotor RPM emergency, the pilot's response, and energy management during the descent. The settling of the helicopter in the muddy ground and the V-belt drive system failure sequence were analyzed. The pilot's PPL training and skill test on the Robinson R44, as well as the Operational Suitability Data (OSD), were evaluated. Survival aspects were also covered.
Conclusions
The report listed findings as to causes and contributing factors, factors that increased risk, and other findings. A safety issue was identified: mandatory training elements as defined in the OSD for R44 helicopters were not properly implemented in the training course.
Safety Actions and Recommendations
Safety recommendations were issued. Appendices include Safety Notice SN-10 regarding fatal accidents caused by low rotor RPM stall and an extract from the RHC R44 Maneuver Guide. The investigation was supported by the NTSB (USA).