Is AD 01-21493 a recurring Airworthiness Directive?

No — AD 01-21493 is a one-time directive. Verify it was complied with in the aircraft's records.

Which aircraft does AD 01-21493 apply to?

AD 01-21493 applies to Boeing — models 720. Serial/part conditions may narrow it to specific aircraft.

Airworthiness Directive 01-21493

one-time

AD 01-21493 · 2001-08-29 · airframe

Airworthiness Directives; Boeing Model 707 and 720 Series Airplanes

What this AD requires

This amendment adopts a new airworthiness directive (AD), applicable to certain Boeing Model 707 and 720 series airplanes, that requires a preventive modification of the front spar fitting on the outboard engine nacelle. This action is necessary to prevent fatigue cracking of the front spar fitting on the outboard engine nacelle, which could reduce the structural integrity of the nacelle, and result in separation of the engine from the airplane. This action is intended to address the identified unsafe condition.

Which aircraft AD 01-21493 applies to

MakesBoeing

Models720

certain

Whether AD 01-21493 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 01-21493 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.