Airworthiness Directive 91-05-21
one-timeAD 91-05-21 · 1991-01-01 · airframe
Airworthiness Directives; which do not incorporate the increased shroud cooling design features of paragraph (b) of this AD, installed on, but not limited t
Which aircraft AD 91-05-21 applies to
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Whether AD 91-05-21 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 91-05-21 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.