Is AD 99-21-24 a recurring Airworthiness Directive?

No — AD 99-21-24 is a one-time directive. Verify it was complied with in the aircraft's records.

Airworthiness Directive 99-21-24

Q: Which aircraft does AD 99-21-24 apply to?

AD 99-21-24 applies to Eurocopter France — models SA-365C, SA-365C1, SA-365C2, SA-365N, SA-365N1, AS-365N2, SA-366G1, SA-365. Serial/part conditions may narrow it to specific aircraft.

one-time

Official AD 99-21-24 · FR doc 99-26712 · 1999-10-14 · airframe

Airworthiness Directives; Eurocopter France Model SA-365C, C1, C2, N, and N1; AS-365N2; and SA-366G1 Helicopters

What this AD requires

This amendment adopts a new airworthiness directive (AD), applicable to Eurocopter France Model SA-365C, C1, C2, N, and N1; AS- 365N2; and SA-366G1 helicopters, that requires inspecting the tightening torque of the main rotor hub blade attach beam spherical thrust bearing bolts (bolts). This AD also requires either applying the specified torque or, if necessary, conducting a dye penetrant inspection for cracks in the metal components. Replacing the spherical thrust bearing (bearing) with an airworthy bearing is also required if a crack is found. This amendment is prompted by reports of cracks in the metal components of the bearing attachment joint. The actions specified by this AD are intended to prevent loosening of bearing bolts in flight, which may cause cracks in the metal components, failure of the bearing, and subsequent loss of control of the helicopter.

Which aircraft AD 99-21-24 applies to

MakesEurocopter France

ModelsSA-365C, SA-365C1, SA-365C2, SA-365N, SA-365N1, AS-365N2, SA-366G1, SA-365, AS-365, SA-366

Whether AD 99-21-24 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 99-21-24 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.