AD 2004-24-04
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| engine | Allison | Engine Company | Airworthiness Directives; Rolls-Royce Corporation (Formerly Allison Engine Company, Allison Gas Turbine Division, and Detroit Diesel Allison) (RRC) Models 250-C30R/3, -C30R/3M, -C47B, and -C47M Turboshaft Engines |
Unsafe Condition
The manufacturer released a redesigned HMU with a dual-element potentiometer to prevent uncommanded and sudden changes in engine power.
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Required Actions
Perform an initial electrical signal inspection of the HMU Power Lever Angle (PLA) potentiometer within 300 flight hours after the effective date. Replace the HMU before further flight if the inspection result is unacceptable. Perform repetitive inspections every 300 flight hours. Replace the HMU with a new design HMU (not specified in this AD) within 600 flight hours after the effective date or by January 31, 2005, whichever occurs earlier.
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Compliance Time
Within 600 flight hours after the effective date or by January 31, 2005, whichever occurs earlier.
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Affected Aircraft
Rolls-Royce Corporation (formerly Allison Engine Company, Allison Gas Turbine Division, and Detroit Diesel Allison) models 250-C30R/3, -C30R/3M, -C47B, and -C47M turboshaft engines with a hydromechanical unit (HMU) part number listed in RRC Alert Commercial Engine Bulletins (ACEB) No. CEB A-73-3103, Revision 4, and No. CEB A-73-6030, Revision 4, dated December 2, 2003.
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Source: Official FAA Source ↗
Retrieved: Apr 6, 2026
Rights: U.S. Government Public Domain
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