Airworthiness Directive · Amendment 39-21606 · Main rotor system
Leonardo S.p.a. (Type Certificates Previously Held by Agusta S.p.A. and AgustaWestland S.p.A.) Helicopters
This AD applies to Leonardo S.p.a. (Type Certificate previously held by Agusta S.p.A.) Model AB139 and AW139 helicopters and Leonardo S.p.a. (Type Certificate previously held by AgustaWestland S.p.A.) Model AW189 helicopters, certificated in any category, with a main rotor (M/R) slip ring part number (P/N) 4G6220V00151 with a serial number (S/N) up to and including S/N 0141, except those marked with an “L” following the S/N, installed.
The FAA is adopting a new airworthiness directive (AD) for Leonardo S.p.a. (Type Certificate previously held by Agusta S.p.A.) Model AB139 and AW139 helicopters and Leonardo S.p.a. (Type Certificate previously held by AgustaWestland S.p.A.) Model AW189 helicopters. This AD was prompted by reports of missing lock wire and loose fasteners. This AD requires a one-time inspection of the main rotor (M/R) slip ring and depending on the outcome, removing the M/R slip ring from service, removing screws and washers from service, applying torque, installing lock wire, and re-identifying the M/R slip ring. This AD also prohibits the installation of certain M/R slip rings. The FAA is issuing this AD to address the unsafe condition on these products.
(1) For an M/R slip ring that has accumulated 900 or more total hours time-in-service (TIS), within 50 hours TIS after the effective date of this AD; and for an M/R slip ring that has accumulated less than 900 total hours TIS, within 300 hours TIS after the effective date of this AD or before accumulating 950 total hours TIS, whichever occurs first:
(i) With the M/R slip ring removed, visually inspect for the presence of each screw, the presence of any ferrule ended safety cable, the correct installation of lock wire 0.20 CRES NAS 33540 P/N MS20995C20 (double-twist lock wire), and any missing double-twist lock wire for each set of upper (connecter) end and lower (pigtail or standpipe) end fasteners of the M/R slip ring as depicted in Figures 1 and 2 of Annex A to Leonardo Helicopters Alert Service Bulletin (ASB) No. 139-472, dated May 9, 2017 (ASB 139-472), or Leonardo Helicopters ASB No. 189-138, dated May 12, 2017 (ASB 189-138), as applicable to your model helicopter. Figures 2 and 3 of Annex A to ASB 139-472 and ASB 189-138 also show examples of a ferrule ended safety cable installed that are not approved.
Note 1 to paragraph (g)(1)(i): Annex A to ASB 139-472 and ASB 189-138 is Moog Service Bulletin SB 16-01, Revision 5, undated.
(ii) If all of the screws are present, there is not any ferrule ended safety cable installed, the double-twist lock wire is correctly installed, and none of the double-twist lock wire is missing on each set of upper end and lower end fasteners of the M/R slip ring, before further flight, mark the letter “L” following the S/N on the identification label by following the Compliance Instructions, paragraph 3) of Annex A to ASB 139-472 or ASB 189-138, as applicable to your model helicopter.
(iii) If a screw is missing from the inner diameter (the connector flange) of the upper end of the M/R slip ring, before further flight, remove the M/R slip ring from service.
(iv) If a screw is missing from the outer diameter of the upper end, from the inner diameter of the lower end (shaft extension attachment area), or from the outer diameter of the lower end, before further flight, install a new screw and washer, apply a torque to 1-1.25 Nm, and install double-twist lock wire by following the Compliance Instructions, paragraphs 9)a) through g) of Annex A to ASB 139-472 or ASB 189-138, as applicable to your model helicopter.
(v) If any double-twist lock wire is not correctly installed, is missing, or if there is a ferrule ended safety cable installed on any set of upper end or lower end fasters of the M/R slip ring, before further flight, remove the incorrectly installed lock wire or ferrule ended safety cable from service, as applicable, and inspect the fastener torque by applying 1-1.25 Nm of torque.
(A) If the torque of a screw installed in the inner diameter (the connector flange) of the upper end of the M/R slip ring is below 1 Nm of torque, do not remove or replace the screw, before further flight, apply a torque of 1-1.25 Nm.
(B) If the torque of a screw installed in the outer diameter of the upper end, in the inner diameter of the lower end (shaft extension attachment area), or in the outer diameter of the lower end is below 1 Nm of torque, before further flight, remove the affected screw and washer from service, install a new screw and washer, and apply a torque of 1-1.25 Nm.
(C) Install double-twist lock wire by following the Compliance Instructions, paragraphs 9)a) through g) of Annex A to ASB 139-472 or ASB 189-138, as applicable to your model helicopter.
(vi) Mark the letter “L” following the S/N on the identification label by following the Compliance Instructions, paragraph 3) of Annex A to ASB 139-472 or ASB 189-138, as applicable to your model helicopter.
(2) As of the effective date of this AD, do not install an M/R slip ring identified in paragraph (c) of this AD unless the requirements of paragraph (g)(1) of this AD have been accomplished.
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.
