Helicopter Incident in Głogów: Rotor RPM Warning During Medical Flight

Incident Overview and Flight Details On June 20, 2017, a professional helicopter pilot and crew from the Zielona Góra branch conducted a medical transport flight under order number 213/R15/2017. The route covered Zielona Góra, Zgorzelec, and Wrocław. During the return leg from Wrocław to the base in Zielona Góra, the aircraft encountered an anomaly in the vicinity of Głogów. ## In-Flight Warning and Crew Response While flying, a brief “Rotor RPM” warning appeared on the warning panel, accompanied by an audible signal indicating low main rotor speed. The pilot silenced the audio alert and, together with the crew, checked the powerplant parameters. The engine and turbine indicators, including the CAD display and main rotor tachometer, showed normal readings with no additional cautions. After confirming the parameters were correct, the pilot decided to continue the flight to the base. ## Landing and Post-Flight Actions During the approach to landing, the red “Rotor RPM” indicator light flashed several times. The helicopter landed without further issues. The pilot reported the event to the Technical Coordination Center, and the aircraft was grounded. ## Maintenance and Return to Service Technical personnel from the Szczecin maintenance station diagnosed the fault and replaced the faulty main rotor speed sensor, serial number 13-169173-22400, with a new unit, serial number 16-16917328816, in accordance with AMM 62-41-00, 8-1. Subsequent tests under AMM 62-4100, 5-2 and AMM 77-10-00, 5-2 were successful. The crew performed a ground check and a control flight, confirming the helicopter was airworthy, and it was returned to service. ## Investigation Findings The State Commission for Aviation Accident Investigation (PKBWL) concluded that the probable cause of the incident was operational wear of the main rotor speed sensor. The operator discussed the event with all LPR operational personnel. The commission did not issue safety recommendations.