Main Rotor Drive – Main Gearbox Bearing Lock-Nut – Replacement
Superseded. Comply with 2019-0174, which replaces this document.
- Published
- Effective
- Deadline
AI-generated summary of the official EASA document. Verify against the PDF before acting.
What to do
Operators must remove the affected main gearbox and replace the bearing lock-nut within the compliance times specified based on accumulated landings, ranging from 1,500 to 2,000 landings or during the next overhaul, whichever occurs first. If landing data is unavailable, flight hours multiplied by six should be used to determine compliance. Installation of serviceable main gearboxes or affected gearboxes with less than 36,000 landings is permitted with required lock-nut replacement.
Summary
EASA Airworthiness Directive 2019-0036 is an airworthiness directive issued by the European Union Aviation Safety Agency affecting Leonardo S.p.A. AB139 and AW139 helicopters. It addresses the replacement of the main gearbox bearing lock-nut part number 3G6320A09151 to prevent potential failure of the main gearbox planetary gears. This directive applies to all serial numbers of the AB139 and AW139 helicopter models.
What changed
This directive introduces a mandatory one-time replacement of the affected main gearbox bearing lock-nut on specified helicopters. It requires removal of the affected main gearbox and replacement of the lock-nut according to Leonardo Alert Service Bulletin 139-567. The directive also allows installation of affected parts under certain conditions with required subsequent lock-nut replacement.
Why it matters
This airworthiness directive is critical for operators and maintenance organizations to prevent possible failure of the main gearbox planetary gears, which could lead to loss of helicopter control. Compliance ensures continued airworthiness and safety of AB139 and AW139 helicopters. It also provides clear instructions and compliance timelines to avoid operational disruptions and regulatory non-compliance.
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