Is AD 99-21-25 a recurring Airworthiness Directive?

Yes — AD 99-21-25 requires a repetitive inspection every 25 hours. Next-due depends on the aircraft's time in service.

Which aircraft does AD 99-21-25 apply to?

AD 99-21-25 applies to Eurocopter France — models SE-3160, SA-315B, SA-316B, SA-316C, SA-319B, SA-315, SA-316, SA-319. Serial/part conditions may narrow it to specific aircraft.

Airworthiness Directive 99-21-25

recurring

Official AD 99-21-25 · FR doc 99-26711 · 1999-10-14 · airframe

Airworthiness Directives; Eurocopter France Model SE.3160, SA.315B, SA.316B, SA.316C, and SA.319B Helicopters

What this AD requires

This amendment adopts a new airworthiness directive (AD) applicable to Eurocopter France Model SE.3160, SA.315B, SA.316B, SA.316C, and SA.319B helicopters with a main gearbox (MGB), all part numbers, not modified in accordance with MOD 072241. This action requires, prior to further flight and thereafter prior to the first flight of each day, inspecting the MGB magnetic plug for metal particles. This AD also requires inspecting the MGB oil filter for metal particles. This amendment is prompted by the failure of a bevel wheel gear attachment bolt (bolt) during testing of an SA.315B MGB. The actions specified in this AD are intended to detect a condition that could cause bolt failure and damage to the MGB, resulting in loss of drive to the main rotor and subsequent loss of control of the helicopter.

Repetitive inspection. Re-inspect every 25 hours. The next-due date/hours depend on this aircraft’s time in service — a records report computes it from the logbooks.

Which aircraft AD 99-21-25 applies to

MakesEurocopter France

ModelsSE-3160, SA-315B, SA-316B, SA-316C, SA-319B, SA-315, SA-316, SA-319

Applies to helicopters with a main gearbox (any part number) not modified in accordance with MOD 072241.

Whether AD 99-21-25 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 99-21-25 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.