Tail Rotor — Double Bearing — Inspection / Replacement
- Published
- Effective
- Deadline
- Replaces
- 2020-0078
AI-generated summary of the official EASA document. Verify against the PDF before acting.
What to do
Operators of affected Airbus Helicopters models must perform repetitive inspections of the tail rotor gearbox chip detector at intervals not exceeding 10 flight hours for Group 1 helicopters and follow specified washing and inspection intervals for Group 2 helicopters. Affected double bearings must be replaced before exceeding 610 flight hours since first installation or within 110 flight hours after 28 October 2019, whichever is later, with the first replacement for Group 2 helicopters required by 31 December 2021. All inspections and corrective actions must follow the applicable Airbus Helicopters Emergency Alert Service Bulletins.
Summary
EASA Airworthiness Directive 2021-0170 is an airworthiness directive addressing inspection and replacement requirements for double bearings with Part Numbers 704A33-651-245 or 704A33-651-246 installed on tail rotor gearboxes (P/N 365A33-6005-09) of Airbus Helicopters AS 365 N2, AS 365 N3, EC 155 B, EC 155 B1, and SA 365 N1 models. The directive mandates repetitive inspections of the tail rotor gearbox chip detector and sets replacement intervals for affected parts to prevent loss of yaw control. It applies to all serial numbers of the specified helicopter models.
What changed
EASA AD 2021-0170 supersedes AD 2020-0078 and introduces reduced inspection intervals for the tail rotor gearbox chip detector to allow earlier detection of bearing degradation. It also introduces a calendar time limit for the first replacement of affected double bearings and updates corrective action criteria based on new testing data. The directive retains previous inspection and replacement requirements but tightens compliance to enhance safety.
Why it matters
This directive is critical for aviation professionals as it addresses a potential unsafe condition that could lead to loss of yaw control due to double bearing failure in the tail rotor gearbox. Operators and maintenance organizations must comply with the updated inspection intervals and replacement schedules to ensure continued airworthiness and prevent in-flight failures. Compliance teams need to track affected parts and ensure timely inspections and replacements to meet regulatory requirements.
More for Airbus Helicopters SA
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- EASA AD 2026-0118Rotors Flight Control – Tail Rotor Actuator – InspectionJun 22, 2026
- EASA AD 2026-0029Tail Rotor Drive — Tail Gear Box Input Flange — Functional ChecksFeb 12, 2026
- EASA PAD 26-017Powerplant — Engine Firewalls — Modification
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