Is AD 98-26-02 a recurring Airworthiness Directive?

Yes — AD 98-26-02 requires a repetitive inspection. Next-due depends on the aircraft's time in service.

Which aircraft does AD 98-26-02 apply to?

AD 98-26-02 applies to Sikorsky — models S-61. Serial/part conditions may narrow it to specific aircraft.

Airworthiness Directive 98-26-02

recurring

Official AD 98-26-02 · FR doc 98-33106 · 1998-12-16 · airframe

Airworthiness Directives; Sikorsky Aircraft Corporation Model S- 61A, D, E, L, N, NM, R, and V Helicopters

What this AD requires

This amendment adopts a new airworthiness directive (AD), applicable to Sikorsky Aircraft Corporation Model S-61A, D, E, L, N, NM, R, and V helicopters, that requires a nondestructive inspection (NDI) for cracks in the main rotor shaft (shaft), and requires removal of any shaft with a crack and replacement with an airworthy shaft. This AD also requires appropriate marking of shafts and log book entries by the operator to determine the shaft retirement life, and establishes a new retirement life for the shaft. This amendment is prompted by four reports of cracks occurring in helicopters that were utilized in repetitive external lift (REL) operations. The actions specified by this AD are intended to detect a fatigue crack in the shaft that could result in shaft structural failure, loss of power to the main rotor, and subsequent loss of control of the helicopter.

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

Which aircraft AD 98-26-02 applies to

MakesSikorsky

ModelsS-61

Main rotor drive shaft; requires NDI for cracks and life-limiting if used in repetitive external lift (REL) operations (>=6 external lifts/flight hour over any 250-hr TIS period); retirement at 2,200 hrs TIS if modified per Sikorsky CSN 6135-10 / ASB 61B35-53, otherwise per ASB 61B35-68 schedule.

Whether AD 98-26-02 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 98-26-02 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.