Airworthiness Directive · Amendment 39-21394 · Tail rotor gearbox
Airbus Helicopters Deutschland GmbH Helicopters
This airworthiness directive (AD) applies to Airbus Helicopters Deutschland GmbH Model MBB-BK117 A-1, MBB-BK117 A-3, MBB-BK117 A-4, MBB-BK117 B-1, MBB-BK117 B-2, MBB-BK117 C-1, and MBB-BK117 C-2 helicopters, certificated in any category.
The FAA is adopting a new airworthiness directive (AD) for Airbus Helicopters Deutschland GmbH Model MBB-BK117 A-1, MBB-BK117 A-3, MBB-BK117 A-4, MBB-BK117 B-1, MBB-BK117 B-2, MBB-BK117 C-1, and MBB- BK117 C-2 helicopters. This AD requires inspecting the tail gearbox (TGB) bellcrank attachment arm (arm) for a crack. This AD was prompted by a report of a cracked TGB arm. 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.
Within 100 hours time-in-service:
(1) Remove the surface coating from the TGB bellcrank attachment arm and using a 5X or higher power magnifying glass, dye-penetrant inspect the TGB arm for a crack and for any dent, nick, and scratch in the area shown in Figure 1 of Airbus Helicopters Alert Service Bulletin (ASB) MBB-BK117 C-2-65A-008 or ASB MBB-BK117-30A-120, each Revision 0 and dated January 31, 2018, as applicable to your model helicopter.
(2) If there is a crack, before further flight, replace the TGB.
(3) If there is a dent, a nick, or a scratch, before further flight, remove the surface material up to 0.2 mm using 80-grit abrasive paper and repeat the dye penetrant inspection. If there is a crack or if the damage cannot be removed, before further flight, replace the TGB.
(4) If there is no crack and no dent, nick, or scratch, before further flight, finish the surface with 600-grit or finer abrasive paper.
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.
