Is AD 2012-21-01 a recurring Airworthiness Directive?

Yes — AD 2012-21-01 requires a repetitive inspection every 300 hours. Next-due depends on the aircraft's time in service.

Which aircraft does AD 2012-21-01 apply to?

AD 2012-21-01 applies to Mdhi — models MD900. Serial/part conditions may narrow it to specific aircraft.

Airworthiness Directive 2012-21-01

recurring

Official AD 2012-21-01 · FR doc 2012-25387 · 2012-10-23 · airframe

Airworthiness Directives; MD Helicopters, Inc.

What this AD requires

We are adopting a new airworthiness directive (AD) to supersede an existing airworthiness directive for MD Helicopters, Inc. (MDHI), Model MD900 helicopters. The existing AD requires a visual inspection, and if necessary, an eddy current inspection of the main rotor lower hub assembly (lower hub) for a crack. If a crack exists, the AD requires replacing the lower hub with an airworthy lower hub before further flight. Because that AD was immediately effective, we declined to require certain long-term actions prior to public comment. This superseding AD will require the same inspections as the existing AD but will also require long-term recurring inspections and replacing the lower hub with an airworthy lower hub. We are issuing this AD to detect a crack in the lower hub and prevent failure of the lower hub and subsequent loss of control of the helicopter.

Repetitive inspection. Re-inspect every 300 hours. The next-due date/hours depend on this aircraft’s time in service — a records report computes it from the logbooks.

Which aircraft AD 2012-21-01 applies to

MakesMdhi

ModelsMD900

Serial-conditional — narrows to serials 5009–?.

Part-conditional — 900R2101008-107.

Applies only to helicopters with main rotor lower hub assembly P/N 900R2101008-107 with serial numbers beginning with 5009.

Whether AD 2012-21-01 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 2012-21-01 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.