Incident Overview
On 27 September 2016, the crew of a Bell-407 helicopter was conducting a flight from Wysogotowo, within the Poznań-Lawica (EPPO) control zone, to Konstancin. After 1 hour and 12 minutes of flight, a yellow warning light illuminated indicating the presence of metal particles (chips) in the main transmission (XSIN CHIP indication). Following the prescribed procedure, the crew initiated a precautionary landing. The landing was executed in a field near Nieborów without further incident.
Precautionary Landing and Inspection
After landing, the engine and onboard systems were shut down. The crew notified the Flight Information Service (FIS) and the operator’s technical department. The Maintenance Organization Manager, who also served as the certifying mechanic for the Bell-407, arrived at the scene. During inspection of the three chip detectors, one metal chip measuring 1×1.5 mm was found on one detector. The chip was removed and the detectors were cleaned. A ground run of the helicopter was then performed from low throttle to 100% NR (main rotor speed). No recurrence of the chip warning was observed. Based on these maintenance actions, the helicopter was released for flight, with appropriate entries made in the aircraft technical log. The chip was inadvertently dropped onto the ground during inspection and could not be recovered due to its size and the nighttime conditions.
Post-Inspection Flight
On 28 September 2016, a preventive re-check of the main transmission chip detectors was carried out. No abnormalities or chips were found. The crew subsequently flew the helicopter to its home base at EPBC (Bemowo). The flight and landing were completed without any issues.
Investigation Outcome
The cause of the incident was not determined. The loss of the metal chip prevented further analysis to identify its origin. The Polish State Commission on Aircraft Accident Investigation (PKBWL) did not issue any safety recommendations. The operator took preventive actions, including briefing all aviation personnel on the incident and emphasizing the need to follow the Bell-407 Aircraft Maintenance Manual procedures regarding chip quantity, shape, and size.