AD 98-19-20
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| engine | CFM International, S.A. | CFM56-7B20 | Airworthiness Directives; CFM International CFM56-7B and -7B/2 Series Turbofan Engines |
| engine | CFM International, S.A. | CFM56-7B20/2 | Airworthiness Directives; CFM International CFM56-7B and -7B/2 Series Turbofan Engines |
| engine | CFM International, S.A. | CFM56-7B22 | Airworthiness Directives; CFM International CFM56-7B and -7B/2 Series Turbofan Engines |
| engine | CFM International, S.A. | CFM56-7B22/2 | Airworthiness Directives; CFM International CFM56-7B and -7B/2 Series Turbofan Engines |
| engine | CFM International, S.A. | CFM56-7B24 | Airworthiness Directives; CFM International CFM56-7B and -7B/2 Series Turbofan Engines |
| engine | CFM International, S.A. | CFM56-7B24/2 | Airworthiness Directives; CFM International CFM56-7B and -7B/2 Series Turbofan Engines |
| engine | CFM International, S.A. | CFM56-7B26 | Airworthiness Directives; CFM International CFM56-7B and -7B/2 Series Turbofan Engines |
| engine | CFM International, S.A. | CFM56-7B26/2 | Airworthiness Directives; CFM International CFM56-7B and -7B/2 Series Turbofan Engines |
| engine | CFM International, S.A. | CFM56-7B27 | Airworthiness Directives; CFM International CFM56-7B and -7B/2 Series Turbofan Engines |
| engine | CFM International, S.A. | CFM56-7B27/2 | Airworthiness Directives; CFM International CFM56-7B and -7B/2 Series Turbofan Engines |
Unsafe Condition
Failure of the hydromechanical unit (HMU) overspeed governor (OSG) spool valve shaft due to out-of-specification conditions or heavy contact/galling on the spool valve, which could result in engine flameout.
AI-generated summary from the source AD text. Verify against the official source before acting.
Required Actions
Inspect HMU OSG spool valves for out-of-specification conditions or heavy contact/galling prior to accumulating 300 hours time since new or within 300 hours time in service since last inspection. Repetitive inspections must be conducted at intervals not exceeding 300 hours TIS. Optional installation of HMU P/N 1853M56P06 terminates inspection requirements.
AI-generated summary from the source AD text. Verify against the official source before acting.
Compliance Time
Required as indicated: initial inspections before 300 hours time since new or within 300 hours TIS since last inspection; repetitive inspections within 300 hours TIS since last inspection.
AI-generated summary from the source AD text. Verify against the official source before acting.
Affected Aircraft
CFM International CFM56-7B and -7B/2 series turbofan engines with HMU P/N 1853M56P04 or 1853M56P05 (AlliedSignal P/N 442008 or 442026).
AI-generated summary from the source AD text. Verify against the official source before acting.
Source: Official FAA Source ↗
Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
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