Airworthiness Directive · Amendment 39-21288 · Tail rotor gearbox
Airbus Helicopters
This AD applies to Airbus Helicopters Model AS-365N2, AS 365 N3, EC 155B, EC155B1, and SA-365N1 helicopters, certificated in any category.
The FAA is adopting a new airworthiness directive (AD) for Airbus Helicopters Model AS-365N2, AS 365 N3, EC 155B, EC155B1, and SA- 365N1 helicopters. This AD requires inspecting the tail rotor gearbox (TGB) housing recess, and depending on the inspection results, performing more in-depth inspections and removing certain parts from service. This AD also prohibits installing a TGB unless it has passed certain inspections and has a new TGB control rod bearing installed. This AD was prompted by the discovery of a foreign object obstructing the oil duct of a TGB control bearing. 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) Within 55 hours time-in-service or 5 months, whichever occurs first: (i) Open the TGB oil filter plug cover (cover) identified as “b” in Detail “A” and Detail “B” in Figure 1 of Airbus Helicopters Emergency Alert Service Bulletin (EASB) No. 65.00.19 or Airbus Helicopters EASB No. 65A008, both Revision 0 and dated July 10, 2019 (EASB 65.00.19 or EASB 65A008), as applicable to your model helicopter, by removing any lockwire, opening the cover (b), and removing the strainer (e) using a screwdriver. Remove the TGB oil filter plug (plug) identified as “h” in Detail “B” in Figure 1 of EASB 65.00.19 or EASB 65A008, as applicable to your model helicopter, by removing the sealing compound at the base of the plug (h), marking the base of the plug (h) and the TGB housing (c), and removing and cleaning the plug (h) and the exterior surface of the TGB housing (c) surrounding the plug (h) installation area.
(ii) Using an adjustable or fixed head borescope with a 6 mm or larger diameter camera probe, inspect for operating oil (oil) retention and visibility of the two T holes in the TGB oil housing recess (housing recess) (towards the rear of the helicopter) identified as “g” in Section C-C in Figure 2 of EASB 65.00.19 or EASB 65A008, as applicable to your model helicopter.
(A) If there is any oil retention in the housing recess (g) and the two T holes are not completely visible as shown in photo 1, in the Accomplishment Instructions, paragraph 3.B.2.b., of EASB 65.00.19 or EASB 65A008, as applicable to your model helicopter, before further flight, remove the TGB control rod and inspect for and remove any foreign objects in the TGB oil duct (oil duct) identified as “k” in Detail “D” of Figure 2 of EASB 65.00.19 or EASB 65A008, as applicable to your model helicopter.
(B) With all of the oil drained from the housing recess (g), inspect for oil retention and visibility of the two T holes in the housing recess (g) as required by paragraph (e)(1)(ii) of this AD.
(1) If there is any oil retention in the housing recess (g) and the two T holes are not completely visible, before further flight, replace the TGB.
(2) If there is no oil retention in the housing recess (g) and the two T holes are completely visible, before further flight:
(i) Inspect for any foreign objects in the oil duct identified as “k” in Section EE of Figure 3 of EASB 65.00.19 or EASB 65A008, as applicable to your model helicopter. If there is any foreign object, before further flight, remove each foreign object.
(ii) Inspect for oil flow at the end of the oil duct (k) BTP (q) cover by following the procedures in the second step through the sixth step, inclusive, of the Accomplishment Instructions, paragraph 3.B.3.b., of EASB 65.00.19 or EASB 65A008, as applicable to your model helicopter.
(iii) If the oil does not flow at the end of the oil duct (k) BTP (q) cover, before further flight, replace the TGB.
(iv) If the oil flows at the end of the oil duct (k) BTP (q) cover, before further flight, remove from service the TGB control rod bearing.
(2) As of the effective date of this AD, do not install a TGB on any helicopter unless, with the non-installed TGB in a level position using shims, the requirements of paragraph (e)(1) of this AD have been accomplished. Unless already done, installation of a new TGB control rod bearing is also required. Accomplishment Instructions, paragraph 3.B.6., of EASB 65.00.19 and EASB 65A008, as applicable to your model helicopter, contain information pertaining to inspecting a non-installed TGB. A TGB with a log card entry showing it has passed the requirements in the Accomplishment Instructions, paragraph 3.B.6., of EASB 65.00.19 and EASB 65A008, as applicable to your model helicopter, is acceptable for compliance with this paragraph.
