Is AD 99-19-23 a recurring Airworthiness Directive?

No — AD 99-19-23 is a one-time directive. Verify it was complied with in the aircraft's records.

Which aircraft does AD 99-19-23 apply to?

AD 99-19-23 applies to Eurocopter — models EC120. Serial/part conditions may narrow it to specific aircraft.

Airworthiness Directive 99-19-23

one-time

Official AD 99-19-23 · FR doc 99-25374 · 1999-10-04 · airframe

Airworthiness Directives; Eurocopter France Model EC 120B Helicopters

What this AD requires

This document publishes in the Federal Register an amendment adopting Airworthiness Directive (AD) 99-19-23 which was sent previously to all known U.S. owners and operators of Eurocopter France Model EC 120B helicopters by individual letters. This AD requires, at specified time intervals, inspecting the engine coupling tube for cracks and replacing any cracked engine coupling tube with an airworthy engine coupling tube. This amendment is prompted by the discovery, during routine maintenance inspections, of three cracked engine coupling tubes caused by structural resonance. The actions specified by this AD are intended to detect a crack in the engine coupling tube which could result in coupling failure, loss of engine drive, and a subsequent forced landing.

Which aircraft AD 99-19-23 applies to

MakesEurocopter

ModelsEC120

Part-conditional — C631A1002101.

Applies where engine coupling tube P/N C631A1002101 is installed. Repetitive 10-hour TIS inspection for cracks; replace any cracked coupling tube before further flight, per Eurocopter Service Telex No. 05-001 EC 120, Version B, dated August 26, 1999.

Whether AD 99-19-23 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 99-19-23 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.