Incident Overview
On September 25, 2017, at 16:30 LMT, a flight instructor and a student pilot were performing training flights at the Sochaczew airfield in a Guimbal Cabri G2 helicopter. During the practice of an autorotation with a throttled engine, after regaining power, the crew intended to execute a flare and transition to a go-around. As the flare maneuver was performed, a sudden drop in engine RPM (below 2000 RPM) occurred. The flight instructor reacted by increasing engine RPM using the twist grip, preventing an uncontrolled ground impact. During the descent, the governor warning light was flashing.
Post-Flight Inspection
After landing and engine shutdown, a check of the onboard systems displayed a message indicating "throttle fault." The CAMO manager and the maintenance organization manager were informed. The helicopter was withheld from further operation. A maintenance mechanic checked the throttle position measurement system in accordance with MM72-A10. No fault was found replicating the in-flight issue, nor during the ground system checks. A test flight was conducted, and no irregularities were observed during the flight or after the subsequent ground system check. The helicopter was returned to service.
Findings and Actions
The cause of the incident was not determined. The operator conducted preventive actions by informing all AOSL personnel of the event. The State Commission on Aircraft Accident Investigation (PKBWL) did not issue any safety recommendations.