Airworthiness Directive · Amendment 39-19421 · Tail rotor gearbox
Bell Helicopter Textron Canada Limited Helicopters
This AD applies to Model 429 helicopters, certificated in any category.
We are publishing a new airworthiness directive (AD) for Bell Helicopter Textron Canada Limited (Bell) Model 429 helicopters. This AD was sent previously to all known U.S. owners and operators of these helicopters as Emergency AD 2018-16-51, dated July 26, 2018, which superseded Emergency AD 2018-15-51, dated July 20, 2018. This AD requires inspecting the tail rotor (T/R) gearbox installation, inspecting the T/R gearbox retaining hardware and support attachment point areas, and replacing each nut. This AD is prompted by two reports of T/R gearbox assemblies loosely attached to the gearbox support. The actions of this AD are intended to address 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) Before further flight, inspect for looseness of the T/R gearbox installation to the T/R gearbox structural support by moving the T/R gearbox output shaft in an upward and downward direction. If the T/R gearbox installation is loose, before further flight, complete the actions required by paragraphs (f)(2)(i) and (ii) of this AD.
(2) Within 5 hours time-in-service, unless already completed as required by paragraph (f)(1) of this AD:
(i) Visually inspect the T/R gearbox retaining hardware and each support attachment point area for evidence of fretting, a crack, and incorrect installation. If there is any evidence of fretting, a crack, or incorrect installation, before further flight, repair in accordance with FAA-approved procedures.
(ii) Inspect each T/R gearbox retaining nut by applying 160 in-lbs (19 Nm) of torque. If the torque of a T/R gearbox retaining nut is below 160 in-lbs (19 Nm), before further flight:
(A) Remove the T/R gearbox and inspect each stud for proper staking, each stud thread for uniformity, each mounting surface for evidence of fretting and cracking, and each mounting hole for elongation. If a stud is not properly staked, a stud thread is not uniform, a mounting surface has evidence of fretting or cracking, or a mount hole is elongated, before further flight, replace the affected parts or repair in accordance with FAA-approved procedures.
(B) Replace each nut with nut part number NAS9926-6L and apply a torque of 160 in-lbs.
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.
