AD 2018-04-11
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Agusta | S.p.A. | Airworthiness Directives; Agusta S.p.A. Helicopters |
Unsafe Condition
Nonconforming thickness in a section of a tail gearbox (TGB) central housing, which can lead to a crack in the TGB central housing and result in the failure of the tail gear rotor transmission and loss of helicopter control.
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Required Actions
Measure the thickness of the central housing in accordance with Leonardo Helicopters Bollettino Tecnico No. 139-274, dated September 14, 2016, and replace the TGB central housing before further flight if the thickness is less than 2.65 mm (0.104 inch).
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Compliance Time
Before accumulating 7,500 hours TIS for helicopters with a TGB central housing with less than 7,500 hours TIS, and within 300 hours TIS for helicopters with a TGB central housing with 7,500 or more hours TIS.
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Affected Aircraft
Agusta S.p.A. Model AB139 and Model AW139 helicopters, certificated in any category, with a tail gearbox (TGB) assembly part number (P/N) 3T6522A00239, 3T6522A00242, 3T6522A00243, or 3T6522A00246 that has a central housing P/N 3T6522A05144 or 3T6522A05146, all serial numbers except those listed in Table 1 of Leonardo Helicopters Bollettino Tecnico No. 139-274, dated September 14, 2016.
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Source: Official FAA Source ↗
Retrieved: Apr 6, 2026
Rights: U.S. Government Public Domain
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