EASA SIB 2010-20: EUROCOPTER helicopters - Main Gear Box - Monitoring of lubricating oils

What to do

Operators should perform daily visual and sensory inspections of MGB lubricating oil after the last flight of the day, checking oil level and magnetic plugs for anomalies. Periodic water content analysis of the oil should be conducted at intervals not exceeding six months and before returning helicopters to service after more than one month of grounding. If water content exceeds 1,000 ppm, disassemble and inspect the Free wheel/MGB coupling as per Eurocopter's maintenance documentation.

Summary

EASA Safety Information Bulletin 2010-20 is a safety information bulletin addressing the monitoring of lubricating oils in the Main Gear Box (MGB) of Eurocopter helicopters, specifically models SA 3180, SA 318B, SA 318C, SE 3160, SA 316B, SA 316C, SA 319B, and SA 315B. The bulletin endorses Eurocopter's recommendations for daily visual and sensory checks of MGB oil and periodic testing for water content to detect early signs of wear or damage. It references Eurocopter Safety Information Notice 2173-S-05 and Service Bulletins 05.101 and 05.43 for detailed procedures.

What changed

This bulletin introduces and endorses Eurocopter's recommendations for enhanced monitoring of MGB lubricating oils, including daily checks of oil appearance, color, and smell, and periodic water content analysis. It establishes a water contamination threshold of 1,000 ppm, above which disassembly and inspection of the Free wheel/MGB coupling are recommended. The bulletin also recommends repeating water content checks every six months and before returning helicopters to service after extended grounding.

Why it matters

The monitoring procedures help aviation professionals detect early signs of wear or damage in the MGB that may not be identified through metal particle analysis alone, thereby preventing potential failures. Regular water content checks reduce the risk of corrosion inside the MGB and free wheel, enhancing helicopter safety and reliability. These recommendations support maintenance teams in preserving aircraft airworthiness and operational readiness.