Is AD 2021-26-18 a recurring Airworthiness Directive?

No — AD 2021-26-18 is a one-time directive. Verify it was complied with in the aircraft's records.

Airworthiness Directive 2021-26-18

Q: Which aircraft does AD 2021-26-18 apply to?

AD 2021-26-18 applies to Airbus Helicopters — models AS-365N2, AS 365 N3, SA-365N1, SA-365C1, SA-365C2, SA-365N, EC 155B, EC155B1. Serial/part conditions may narrow it to specific aircraft.

one-time

Official AD 2021-26-18 · FR doc 2021-28471 · 2022-01-05 · airframe

Airworthiness Directives; Airbus Helicopters

What this AD requires

The FAA is superseding Airworthiness Directive (AD) 2020-21-01 for certain Airbus Helicopters Model AS-365N2, AS 365N3, EC 155B, EC155B1, and SA-365N1 helicopters. AD 2020-21-01 required modifying the main gearbox (MGB) tail rotor (T/R) drive flange installation. 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 MGB T/R drive flange. This AD continues to require modifying the MGB T/R drive flange installation, and includes additional helicopters in the applicability for the required actions. The FAA is issuing this AD to address the unsafe condition on these products.

Which aircraft AD 2021-26-18 applies to

MakesAirbus Helicopters

ModelsAS-365N2, AS 365 N3, SA-365N1, SA-365C1, SA-365C2, SA-365N, EC 155B, EC155B1, AS-365, SA-365, EC155

Model AS-365N2, AS 365 N3, and SA-365N1 helicopters, all serial numbers on which Airbus Helicopters modification 0763B64 has been embodied, except those on which modification 0763C81 has been embodied. Model SA-365C1, SA-365C2, and SA-365N helicopters, all serial numbers on which modification 0763B64 has been embodied. Model EC 155B and EC155B1 helicopters, all serial numbers, except those on which modification 0763C81 has been embodied.

Whether AD 2021-26-18 actually applies to your aircraft (by serial and installed parts) and whether it’s already complied with comes from that aircraft’s records.

How AD compliance is recorded

A valid compliance record (14 CFR 43.9) states:

Method of compliance — The specific action taken (inspected, replaced, modified) and to what revision.

Date — When the work was done.

Aircraft time — Total time in service / tach at compliance — how recurring next-due is computed.

Signature & certificate — The A&P/IA who returned it to service, with certificate number.

Is AD 2021-26-18 complied with on your aircraft?

Tailplate reads a tail number’s logbooks and matches every applicable AD — including this one — to its compliance evidence, with recurring next-due dates computed.

Look up a tail number →Read the full directive (Federal Register)

Applicability is derived from the FAA directive corpus and is advisory, not a legal airworthiness determination. Compliance is established only from an aircraft’s actual records.