Is AD 91-21-10 a recurring Airworthiness Directive?

No — AD 91-21-10 is a one-time directive. Verify it was complied with in the aircraft's records.

Which aircraft does AD 91-21-10 apply to?

AD 91-21-10 applies to Boeing — models 767. Serial/part conditions may narrow it to specific aircraft.

Airworthiness Directive 91-21-10

one-time

AD 91-21-10 · 1991-01-01 · airframe

Airworthiness Directives; BOEING Model 767 Series Airplanes

Which aircraft AD 91-21-10 applies to

MakesBoeing

Models767

Model 767 series airplanes, Groups 1, 2, and 3, as listed in Boeing Alert Service Bulletin [number truncated]. Offset Gearbox Inspection and Interim Rework per Boeing Alert Service Bulletin 767-27A0095, Revision 1, dated February 22, 1990; Revision 2, dated January [date truncated].

Whether AD 91-21-10 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 91-21-10 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 →

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.