Is AD 2021-26109 a recurring Airworthiness Directive?

No — AD 2021-26109 is a one-time directive. Verify it was complied with in the aircraft's records.

Which aircraft does AD 2021-26109 apply to?

AD 2021-26109 applies to De Havilland Canada — models DHC-8-401, DHC-8-402, DHC-8. Serial/part conditions may narrow it to specific aircraft.

Airworthiness Directive 2021-26109

one-time

AD 2021-26109 · 2021-12-01 · airframe

Airworthiness Directives; De Havilland Aircraft of Canada Limited (Type Certificate Previously Held by Bombardier, Inc.) Airplanes

What this AD requires

The FAA is adopting a new airworthiness directive (AD) for certain De Havilland Aircraft of Canada Limited Model DHC-8-401 and - 402 airplanes. This AD was prompted by reports of loss of hydraulic fluid and annunciation of the check fire detect light. This AD requires doing a detailed visual inspection for chafing and proper clearance of the left-hand (LH) and right-hand (RH) main landing gear (MLG) primary zone advanced pneumatic detector (APD) sensing lines, the hydraulic tube assemblies, and the surrounding structure, and doing all applicable corrective action. The FAA is issuing this AD to address the unsafe condition on these products.

Which aircraft AD 2021-26109 applies to

MakesDe Havilland Canada

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

Serial-conditional — narrows to serials 4001–4001, 4003–4614.

Whether AD 2021-26109 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 2021-26109 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.