Is AD 98-21-23 a recurring Airworthiness Directive?

Yes — AD 98-21-23 requires a repetitive inspection. Next-due depends on the aircraft's time in service.

Which aircraft does AD 98-21-23 apply to?

AD 98-21-23 applies to Cfm International — models CFM56-7B, CFM56. Serial/part conditions may narrow it to specific aircraft.

Airworthiness Directive 98-21-23

recurring

Official AD 98-21-23 · FR doc 98-27464 · 1998-10-16 · turbine engine

Airworthiness Directives; CFM International, S.A. CFM56-7B Series Turbofan Engines

What this AD requires

This amendment adopts a new airworthiness directive (AD) that is applicable to CFM International, S.A. (CFMI) CFM56-7B series turbofan engines. This action supersedes telegraphic AD T98-18-51 that currently requires an inspection of electronic engine control (EEC) fault messages on both engines for the presence of any of the hydromechanical unit (HMU) fuel metering valve (FMV) signal faults identified in the All Operators Wire every 20 flight cycles or 3 calendar days, whichever occurs first, and, if necessary, removing the HMU and replacing it with a serviceable HMU. This action also requires installation of improved EEC software that constitutes terminating action to the repetitive fault message inspections. This amendment is prompted by development of improved EEC software that obviates the need for the repetitive fault message inspections. The actions specified by this AD are intended to prevent an uncommanded engine acceleration event, or inflight engine shutdown.

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 98-21-23 applies to

MakesCfm International

ModelsCFM56-7B, CFM56

Part-conditional — 1853M78P07, 1853M78P08, 1853M78P10, 1853M78P11.

Applies to engines with electronic engine control (EEC) software P/N 1853M78P07, 1853M78P08, 1853M78P10, or 1853M78P11 installed.

Whether AD 98-21-23 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 98-21-23 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.