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Airworthiness Directive 2021-18-17

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Official AD 2021-18-17 · FR doc 2021-24864 · 2021-11-15 · airframe

Airworthiness Directives; The Boeing Company Airplanes

What this AD requires

The FAA is superseding Airworthiness Directive (AD) 2012-21- 08, which applied to certain The Boeing Company Model 737-600, -700, - 700C, -800, and -900 series airplanes. AD 2012-21-08 required inspecting for part numbers of the operational program software (OPS) of the flight control computers (FCCs) and installing and testing an updated version of the FCC OPS. This AD was prompted by reports that during autopilot coupled instrument landing system (ILS) approaches, the airplane did not capture or track the glideslope correctly. This AD retains the requirement to inspect for part numbers of the OPS of the FCCs, and adds a new requirement to update the version of the FCC OPS if necessary. This AD also expands the applicability to include The Boeing Company Model 737-900ER series airplanes. The FAA is issuing this AD to address the unsafe condition on these products.

Which aircraft AD 2021-18-17 applies to

MakesBoeing
Models737-600, 737-700, 737-700C, 737-800, 737-900, 737-900ER, 737

Whether AD 2021-18-17 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 2021-18-17 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.