Airworthiness directives › 2021-26-18
AD 2021-26-18 Airworthiness Directives; Airbus Helicopters
Applicability*9
This AD applies to the Airbus Helicopters model helicopters, certificated in any category, as identified in paragraphs (c)(1) through (3) of this AD. (1) Model AS-365N2, AS 365 N3, and SA-365N1, all serial numbers on which Airbus Helicopters modification 0763B64 has been embodied, except those on which Airbus Helicopters modification 0763C81 has been embodied. (2) Model SA-365C1, SA-365C2, and SA-365N, all serial numbers on which Airbus Helicopters modification 0763B64 has been embodied. (3) Model EC 155B and EC155B1, all serial numbers, except those on which Airbus Helicopters modification 0763C81 has been embodied.
Compliance
Comply with this AD within the compliance times specified, unless already done.
Required actions
This paragraph restates the requirements of paragraph (e) of AD 2020-21-01 with no changes. Within 600 hours time-in-service after November 12, 2020 (the effective date of AD 2020-21-01): (1) For Model AS-365N2, AS 365N3, and SA-365N1 helicopters: (i) Without removing the tail drive shaft flange (a), remove the sliding flange (b) from the flexible coupling (c) as shown in Detail “B” of Figure 1, PRE MOD, of Airbus Helicopters Alert Service Bulletin (ASB) No. AS365-63.00.19, Revision 1, dated January 31, 2019 (ASB AS365-63.00.19, Revision 1); replace the 3 bolts (d) and remove from service the 3 washers (e). (ii) Install the sliding flange (b) with aft output stop (1) part number (P/N) 365A32-7836-20 as shown in Detail “B” of Figure 1, POST MOD, of ASB AS365-63.00.19, Revision 1, and by following the Accomplishment Instructions, paragraph 3.B.2.b, of ASB AS365-63.00.19, Revision 1. (2) For Model EC 155B and EC155B1 helicopters with modification 0763B64 embodied: (i) Without removing the Shur-Lok nut (a), remove the sliding flange (b) from the flexible coupling (c) as shown in Detail “B” of Figure 1, PRE MOD, of Airbus Helicopters ASB No. EC155-63A013, Revision 1, dated January 31, 2019 (ASB EC155-63A013, Revision 1); replace the 3 bolts (d) and remove from service the 3 washers (e). (ii) Install the sliding flange (b) with aft output stop (1) P/N 365A32-7836-20 as shown in Detail “B” of Figure 1, POST MOD, of ASB EC155-63A013, Revision 1, and by following the Accomplishment Instructions, paragraph 3.B.2.b, of ASB EC155-63A013, Revision 1. Note 1 to paragraph (g)(2)(ii): ASB EC155-63A013, Revision 1 refers to the “aft output stop” as “rear output stop.”
Unsafe condition
This AD was prompted by several reported occurrences of loss of tightening torque of the Shur-Lok nut, which serves as a retainer of the main gear box (MGB) tail rotor (T/R) drive flange. The FAA is issuing this AD to detect and address loss of tightening torque of the Shur-Lok nut. The unsafe condition, if not addressed, could result in loosening of the Shur-Lok nut, possibly resulting in disengagement of the Shur-Lok nut threads, reduction of T/R drive control, rear transmission vibrations, and subsequent reduced control of the helicopter.
Affected ADs
This AD replaces AD 2020-21-01, Amendment 39-21274 (85 FR 63440, October 8, 2020) (AD 2020-21-01).
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