Superseded. This AD was superseded by AD 2022-27-03. Verify which one applies to your serial and effectivity before any maintenance action.
AD 2021-20-10
Effective 11/22/2021 · Published 10/18/2021
Airworthiness Directives; Leonardo S.p.a. Helicopters
Summary
The FAA is adopting a new airworthiness directive (AD) for certain Leonardo S.p.a. Model AB139 and AW139 helicopters. This AD was prompted by a report of several occurrences of a cracked main gearbox (MGB) spherical bearing lock nut (lock nut). This AD requires removing from service a certain part-numbered MGB lock nut that is installed on certain part-numbered MGBs and replacing it with newly designed MGB lock nut.…