AD 2021-12-06
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Airbus | Helicopters Model AS-365N2 | Airworthiness Directives; Airbus Helicopters |
Unsafe Condition
Failure of a second stage planet gear of the main gearbox (MGB) due to spalling and cracking of the planet gear assembly, which is more susceptible to this issue due to higher outer race contact pressures.
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Required Actions
Replacing the main gearbox (MGB) before further flight for helicopters with a Type X planet gear assembly with a certain serial number installed, or replacing the MGB within 300 hours time-in-service (TIS) or before any planet gear assembly accumulates 1,300 hours TIS since new, whichever occurs first, for helicopters with no Type X planet gear assembly installed but at least one Type Y planet gear assembly with a certain serial number installed. As an alternative to replacing the MGB, replacing the epicyclic reduction gear module in the affected MGB. Inspecting the lower MGB magnetic plugs for particles within 10 hours TIS and thereafter before the first flight of the day or at intervals not to exceed 10 hours TIS, whichever occurs first, and replacing the MGB if particles are detected.
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Compliance Time
Before further flight, or within 300 hours TIS or before any planet gear assembly accumulates 1,300 hours TIS since new, whichever occurs first.
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Affected Aircraft
Airbus Helicopters Model AS-365N2, AS 365 N3, SA-365N, and SA-365N1 helicopters, with at least one Type X or Y planet gear assembly with a certain serial number installed on the main gearbox (MGB).
AI-generated summary from the source AD text. Verify against the official source before acting.
Source: Official FAA Source ↗
Retrieved: Apr 6, 2026
Rights: U.S. Government Public Domain
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