Is AD 2012-21-12 a recurring Airworthiness Directive?

No — AD 2012-21-12 is a one-time directive. Verify it was complied with in the aircraft's records.

Which aircraft does AD 2012-21-12 apply to?

AD 2012-21-12 applies to Bombardier — models DHC-8-400, DHC-8-401, DHC-8-402, DHC-8. Serial/part conditions may narrow it to specific aircraft.

Airworthiness Directive 2012-21-12

one-time

Official AD 2012-21-12 · FR doc 2012-26077 · 2012-10-30 · airframe

Airworthiness Directives; Bombardier, Inc. Airplanes

What this AD requires

We are adopting a new airworthiness directive (AD) for certain Bombardier, Inc. Model DHC-8-400 series airplanes. This AD was prompted by cases of on-ground failure of the screw cap or end cap of hydraulic accumulators on other airplane models, resulting in high-energy impact damage to adjacent systems and structure. This AD requires inspecting for a part number and replacing the affected parking brake hydraulic accumulator, and relocating the parking brake accumulator, on the subject airplanes. We are issuing this AD to prevent failure of the screw caps and/or end caps of the parking brake hydraulic accumulator, which could result in damage to the airplane's primary structures, with potential adverse effect on the airplane's controllability.

Which aircraft AD 2012-21-12 applies to

MakesBombardier

ModelsDHC-8-400, DHC-8-401, DHC-8-402, DHC-8

Serial-conditional — narrows to serials 4001–4346.

Whether AD 2012-21-12 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 2012-21-12 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.