What happened
On October 2, 2018, an EC 135 P2+ helicopter, operated by LPR, was performing a HEMS (Helicopter Emergency Medical Service) flight from EPPL Płock to Trzcianka. During the flight, the mission was canceled, and the crew initiated a return to Płock.
While on final approach to EPPL Płock at an altitude of approximately 80 feet and a speed of 20 knots, the pilot's seat unexpectedly shifted backward along its longitudinal axis. In response to this sudden movement, the pilot instinctively pulled the cyclic control toward himself while simultaneously moving the collective lever upward. This sequence of inputs resulted in the engine torque (TQ) exceeding the allowable limits.
Despite the excursion, the aircraft landed safely without further incident. Following the landing, the Technical Coordination Center was notified of the event.
The investigation
Investigators reviewed data from the UMS/PGS system to assess the extent of the torque exceedance. The analysis confirmed that the left engine reached a maximum TQ of 90.2% for 0.375 seconds, while the right engine reached a maximum TQ of 91.4% for 0.500 seconds.
According to the Aircraft Maintenance Manual (AMM 05-51-00, 6-8), these exceedances necessitated a Category D inspection within five hours of operation. This inspection was performed within the required timeframe and yielded positive results, confirming no structural or mechanical damage from the event.
Findings
- The primary cause of the seat movement was accumulated debris or contaminants near the seat lock latch mechanism, which allowed the seat to shift backward.
- The pilot's instinctive reaction to the seat movement caused the simultaneous upward movement of the cyclic and collective, leading to the torque exceedance.