What happened
On March 9, 2017, a crew from the Lublin branch of the Polish Medical Air Rescue (LPR) conducted a Helicopter Emergency Medical Service (HEMS) flight to the town of Tarnawka. The mission was completed successfully and without incident. However, following standard operating procedures, the crew reviewed the recordings from the UMS/PGS system to check for any flight parameter deviations.
During this review, the crew identified that torque (TQ) limits had been exceeded on both engines. Specifically, the number 1 engine reached a maximum torque of 70.2% for a duration of 10.75 seconds, while the number 2 engine reached 70.8% for the same duration. The crew noted that they did not observe these exceedances while the aircraft was in flight.
The investigation
Following the discovery of the exceedances, the investigation focused on the technical implications of the recorded data. According to maintenance manual MSM 05-51-00, these specific deviations required a Category B maintenance inspection to be performed within the next five hours of aircraft operation. This inspection included cleaning the main gearbox oil filter, inspecting the chip detectors in the main and final gearboxes, and examining the main rotor hub. All required maintenance tasks were completed within the mandated timeframe, and the EC 135 P2+ was confirmed to be airworthy.
Findings
- The crew did not notice the torque exceedances during the actual flight operations.
- The primary cause of the event was improper distribution of attention during the final phase of the helicopter's acceleration.
- The aircraft was maintained in accordance with technical requirements following the discovery of the data discrepancies.