What happened
On September 27, 2016, a Bell 407 helicopter was conducting a flight from the Wysogotowo area within the EPPO CTR toward Konstancin. Approximately 72 minutes into the flight, the crew observed the XSIN CHIP warning light, indicating the presence of metal particles in the main gearbox. Following established emergency procedures, the crew initiated a precautionary landing in an unprepared field in the vicinity of Nieborów. The landing was completed without incident.
Following the shutdown of the engines and onboard systems, the crew notified Flight Information Service (FIS) and the operator's technical department. A maintenance manager, acting as a mechanic, arrived at the scene to inspect the three chip detectors. During the inspection, a single metal particle measuring approximately 1x1.5 mm was identified in one of the detectors. After the particle was removed and the detectors were cleaned, a ground run-up to 100% NR (main rotor RPM) was performed, which did not trigger a recurrence of the warning.
The investigation
The investigation focused on identifying the source of the metallic debris. While the particle was identified, it was lost during the inspection process when it fell onto the ground; due to the small size of the fragment and the fact that maintenance was being conducted at night, the particle could not be recovered. Consequently, a metallurgical analysis to determine the origin of the debris could not be performed. A follow-up inspection of the main gearbox chip detectors was conducted the following day, September 28, 2016, which yielded no further irregularities.
Findings
- The primary cause of the incident could not be determined because the loss of the metal particle prevented a detailed analysis of its composition and origin.
- The crew successfully followed standard operating procedures by executing a precautionary landing upon detection of the warning.