What happened
On August 28, 2017, a crew operating for the Gliwice branch of the Polish Medical Air Rescue (LPR) was conducting a medical mission involving a patient pickup and a subsequent flight to the Children's Health Center in Katowice. The flight proceeded normally until the approach phase for landing. During the approach, the pilot observed a "XMSN CHIP" warning on the Crew Alerting Display (CAD), indicating the presence of metal particles in the main gearbox.
Following the landing and the shutdown of the EC135 P2+, the pilot reported the warning to the Technical Coordination Center. The aircraft was immediately removed from service for inspection.
The investigation
Technical personnel from the Warsaw Babice maintenance station performed an inspection in accordance with the Aircraft Maintenance Manual (AMM). The mechanic removed the main gearbox chip sensor and confirmed the presence of a metal particle, classified as category "C".
On August 29, 2017, maintenance crews performed an oil filter replacement and a main gearbox flush, following the prescribed AMM procedures. After completing these tasks, a leak test of the main gearbox oil system was conducted with positive results, allowing the aircraft to be conditionally returned to service.
Findings
- The investigation determined that the metal particle had been resting at the bottom of the gearbox.
- The particle was likely dislodged from the bottom of the transmission during normal operations, subsequently triggering the sensor during the flight.