Airworthiness Directive · Amendment 39-22288 · Main rotor gearbox
Leonardo S.p.a. Helicopters
This AD applies to Leonardo S.p.a. Model AB139 and AW139 helicopters, certificated in any category, with a main rotor gearbox (MGB) part number (P/N) 3G6320A00131, 3G6320A00132, 3G6320A00133, 3G6320A00134, 3G6320A00135, 3G6320A00136, 3G6320A22031, 4G6320A00132, or 4G6320A00133, and MGB spherical bearing lock nut (lock nut) P/N 3G6320A09151 installed.
The FAA is superseding Airworthiness Directive (AD) 2021-20-10 for certain Leonardo S.p.a. Model AB139 and AW139 helicopters. AD 2021- 20-10 required removing from service a certain part-numbered main gearbox (MGB) spherical bearing lock nut (lock nut) that is installed on certain part-numbered MGBs and replacing it with a newly designed MGB lock nut. AD 2021-20-10 also prohibited installing any MGB with the affected MGB lock nut and prohibited installing any affected MGB lock nut on any helicopter. Since the FAA issued AD 2021-20-10, it was discovered that a part number (P/N) was incorrectly listed and that the applicability needed to be clarified. This AD retains the requirements of AD 2021-20-10 and clarifies the applicability. The FAA is issuing this AD to address the unsafe condition on these products.
(1) Within 100 hours time-in-service, or during the next scheduled MGB overhaul, whichever occurs first after November 22, 2021 (the effective date of AD 2021-20-10), remove each MGB lock nut P/N 3G6320A09151 from service and replace with MGB lock nut P/N 3G6320A09152 in accordance with Annex A, steps 1 through 17, of Leonardo Helicopters Alert Service Bulletin No. 139-609, Revision A, dated April 13, 2021, except you are not required to send parts to Leonardo Helicopters.
Note 1 to paragraph (g)(1): Leonardo Helicopters service information refers to an MGB lock nut as a ring nut.
(2) As of November 22, 2021 (the effective date of AD 2021-20-10), do not install any MGB having MGB lock nut P/N 3G6320A09151 on any helicopter, and do not install any MGB lock nut P/N 3G6320A09151 on any helicopter.
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
