Airworthiness Directive · Amendment 39-19207 · Tail rotor control system
Agusta S.p.A. Helicopters
This AD applies to 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 Technico No. 139-274, dated September 14, 2016.
We are adopting a new airworthiness directive (AD) for Agusta S.p.A. Model AB139 and Model AW139 helicopters. This AD requires inspecting the thickness of the tail gearbox (TGB) central housing (housing). This AD was prompted by reports that the housing thickness does not conform to its type design. The actions of this AD are intended to detect and correct an unsafe condition on these products.
You are responsible for performing each action required by this AD within the specified compliance time unless it has already been accomplished prior to that time.
(1) For helicopters with a TGB central housing with less than 7,500 hours time-in-service (TIS), before accumulating 7,500 hours TIS, measure the thickness of the central housing in accordance with the Compliance Instructions, Part I paragraphs 1. and 2., of Leonardo Helicopters Bollettino Tecnico No. 139-274, dated September 14, 2016 (BT 139-274). If the thickness is less than 2.65 mm (0.104 inch), replace the TGB central housing before further flight.
(2) For helicopters with a TGB central housing with 7,500 or more hours TIS, within 300 hours TIS, ultrasonic inspect the TGB in accordance with the Compliance Instructions, Part II paragraphs 4. through 4.5 of BT 139-274. If the thickness is less than 2.65 mm (0.104 inch), replace the TGB before further flight.
(3) After the effective date of this AD, do not install a central housing P/N 3T6522A05144 or 3T6522A05146, all serial numbers except those listed in Table 1 of BT 139-274, on any helicopter unless it has passed inspection in accordance with paragraph (e)(1) of this AD.
The aircraft, engines and makers this AD names, by the model designations in its text. A model listed here may still be outside the AD's serial ranges.
Aircraft
