Is AD 2021-09-17 a recurring Airworthiness Directive?

No — AD 2021-09-17 is a one-time directive. Verify it was complied with in the aircraft's records.

Which aircraft does AD 2021-09-17 apply to?

AD 2021-09-17 applies to Bombardier — models BD-100-1A10, BD-100. Serial/part conditions may narrow it to specific aircraft.

Airworthiness Directive 2021-09-17

one-time

Official AD 2021-09-17 · FR doc 2021-10467 · 2021-05-19 · airframe

Airworthiness Directives; Bombardier, Inc., Airplanes

What this AD requires

The FAA is adopting a new airworthiness directive (AD) for certain Bombardier, Inc., Model BD-100-1A10 airplanes. This AD was prompted by a report that the inboard multi-function spoiler (MFS) surfaces failed to deploy, which was caused by missing notches on the piston seal of the MFS power control units (PCUs). This AD requires an inspection to determine if affected MFS PCUs are installed, and replacement of affected MFS PCUs. The FAA is issuing this AD to address the unsafe condition on these products.

Which aircraft AD 2021-09-17 applies to

MakesBombardier

ModelsBD-100-1A10, BD-100

Serial-conditional — narrows to serials 20003–20457, 20501–22999.

Whether AD 2021-09-17 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 2021-09-17 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.