Airworthiness Directive · Amendment 39-21493 · Main rotor drive system
Leonardo S.p.a. Helicopters
This AD applies to Leonardo S.p.a. Model AB412 helicopters, certificated in any category, with a serial number up to 25669 inclusive, with a spiral bevel gear part number 204-040-701-103 with a serial number identified in Table 1 of Finmeccanica Helicopter Division Alert Bollettino Tecnico No. 412-146, Revision A, dated July 7, 2016 (Alert BT 412-146 Rev A).
The FAA is adopting a new airworthiness directive (AD) for certain Leonardo S.p.a. Model AB412 helicopters. This AD was prompted by a cracked spiral bevel gear. This AD requires a one-time visual inspection and a recurring fluorescent magnetic particle inspection (FMPI) of affected spiral bevel gears for a crack, and depending on the inspection results, removing the spiral bevel gear from service. This AD also prohibits installing an affected spiral bevel gear unless it has recently passed an FMPI. The FAA is issuing this AD to address the unsafe condition on these products.
(1) Within 10 hours time-in-service (TIS) after the effective date of this AD:
(i) Visually inspect the spiral bevel gear teeth for a crack by following the Accomplishment Instructions, part I, paragraphs 9. and 10., of Alert BT 412-146 Rev A.
(ii) If there is a crack, before further flight, remove the spiral bevel gear from service.
(iii) If there is not a crack, within 100 hours TIS following paragraph (g)(1)(i) of this AD and thereafter at intervals not to exceed 300 hours TIS, fluorescent magnetic particle inspect the spiral bevel gear for a crack by following the Accomplishment Instructions, part II, paragraph 3., of Alert BT 412-146 Rev A. If there is a crack, before further flight, remove the spiral bevel gear from service.
(2) As of the effective date of this AD, do not install a spiral bevel gear that is identified in paragraph (c) of this AD unless the actions required by paragraph (g)(1)(iii) have been previously accomplished within less than 300 hours TIS.
