Is AD 87-21-07 R1 a recurring Airworthiness Directive?

No — AD 87-21-07 R1 is a one-time directive. Verify it was complied with in the aircraft's records.

Airworthiness Directive 87-21-07 R1

Q: Which aircraft does AD 87-21-07 R1 apply to?

AD 87-21-07 R1 applies to Gulfstream American (Aero Commander), Twin Commander Aircraft Llc — models 500, 500-A, 500-B, 500-S, 500-U, 520, 560, 560-A. Serial/part conditions may narrow it to specific aircraft.

one-time

AD 87-21-07 R1 · 1987-01-01 · airframe

Airworthiness Directives; Airplanes ACTION: SUMMARY: DATES: Effective May 5, 1989. ADDRESSES: FOR FURTHER INFORMATION CONTACT: SUPPLEMENTARY INFORMATION: RE

Which aircraft AD 87-21-07 R1 applies to

MakesGulfstream American (Aero Commander)Twin Commander Aircraft Llc

Models500, 500-A, 500-B, 500-S, 500-U, 520, 560, 560-A, 560-E, 560-F, 680, 680-E, 680-F, 680-F(P), 680-FL, 680-FL(P), 685, 700, 720

Amendment effective May 5, 1989; Gulfstream (Aero Commander)/Twin Commander model line per FAA type-certificate footer list.

Whether AD 87-21-07 R1 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 87-21-07 R1 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.