Eurocopter EC 135 P2+ Torque Exceedance During Training Flight

Incident Overview and Investigation Details On 3 October 2016, an incident involving a Eurocopter EC 135 P2+ was recorded by the Polish State Commission for Aviation Accident Investigation (PKBWL) under case number 2624/16. The event occurred near Jeżów Sudecki, Poland, and was classified as an incident with no injuries. The investigation was supervised by Mieczysław Wyszogrodzki and conducted by the LPR factory commission, concluding on 28 December 2016. ## Operational Context and Flight Profile The helicopter was operating training flights from Jeżów Sudecki airfield (EPJS). The mission involved rescue training using rope techniques approved by the LPR Training Department in cooperation with mountain rescue services. The flight also included an Operational Proficiency Check (OPC) featuring a simulated single-engine failure in accordance with the operational manual. The crew relocated the helicopter to a designated landing site east of Strużnica, within the Jelenia Góra (EPJG) ATZ. During the initial phase, the helicopter carried a takeoff weight of 2,814 kg, below the maximum allowable weight of 2,858 kg for the conditions. After approximately 30 minutes of training involving lowering and recovering GOPR rescuers via ropes, the crew prepared for the simulated engine failure exercise. At the start of this phase, the helicopter's weight was approximately 2,700 kg, with three GOPR rescuers on board. ## Sequence of Events The controlled pilot performed a hover and initiated a vertical climb. At approximately 75 feet, the controlling pilot switched the right engine from FLIGHT to IDLE, simulating a right engine failure. The helicopter entered a vertical descent with decreasing main rotor RPM within the allowable range. The vertical descent rate increased, reaching a maximum of 2,144 ft/min. To reduce the descent rate, the controlled pilot increased the collective and power levers to maximum, resulting in a transient torque exceedance: 95.79% on the left engine and 96.334% on the right engine for 0.1 seconds. When main rotor RPM dropped below 92%, the training mode was deactivated, and the helicopter returned to full two-engine operation. After landing, the controlling pilot switched the training mode off. The controlled pilot completed the return flight to EPJS without further issues. The crew reported the torque exceedance to the Technical Coordination Center, LPR Safety Management Department, and Airbus Helicopters Deutschland. The helicopter was grounded pending inspection. ## Post-Incident Actions and Probable Cause Following consultation with Airbus Helicopters Deutschland, technical personnel in Szczecin performed an inspection in accordance with MSM 05-51-00, 6-8, covering categories A through E, without removing the main rotor blades. The helicopter was subsequently returned to service. The probable cause of the transient torque exceedance was an unfavorable wind direction from the mountain slope, coming from the rear-left/left relative to the helicopter's longitudinal axis. A contributing factor was an excessive vertical descent rate. ## Preventive Measures The operator briefed all operational personnel on the incident and incorporated the assessment of meteorological phenomena during mountain operations into periodic training. PKBWL did not issue safety recommendations.