Event Overview
On 1 May 2019, the crew of a helicopter operated by Lotnicze Pogotowie Ratunkowe (LPR) at Sokołów Podlaski received a medical evacuation mission to Wólka Dolna. The flight to the call site, including start, climb, transit, and landing, proceeded without issues. After boarding the patient, the crew started the helicopter intending to fly to the Provincial Hospital in Siedlce.
Warning and Decision
While the engines were operating at idle power, the Caution and Advisory Display (CAD) showed an XMSN CHIP caution, indicating metal chips in the main gearbox. Other engine parameters remained normal. The commander decided to abort the mission, shut down the engines, and after consulting the Technical Coordination Center (CKT), grounded the helicopter at the location.
Technical Findings
Technical personnel arrived and, based on maintenance documentation (CRS 035/007/DXCC/3/1), found a category C chip on one sensor. The chip and oil samples from the main gearbox were sent to a laboratory for analysis. The helicopter was temporarily returned to service for 5 flight hours pending results. It was then ferried to the base in Sokołów Podlaski and later to the maintenance station in Warsaw-Babice.
Laboratory Results and Repair
Before the 5-hour operational limit expired, laboratory results indicated elevated iron levels in the oil, and the chip most likely originated from the seal of a one-way clutch. Technicians disassembled both one-way clutches, polished the sealing elements of the engine shaft couplings, reassembled the shafts and clutches, and performed a functional test, which was successful.
Outcome
The helicopter was returned to service. The investigation determined that the cause of the incident was operational wear of the sealing element of the one-way clutch. No safety recommendations were issued by the Polish State Commission on Aircraft Accident Investigation (PKBWL).