Airworthiness Directive · Amendment 39-13880 · 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
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
This AD applies to 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 that have a hydromechanical unit (HMU) with a part number (P/N) listed in 1.A. Group A of RRC Alert Commercial Engine Bulletins (ACEB) No. CEB A-73-3103, Revision 4, dated December 2, 2003; and No. CEB A-73-6030, Revision 4, dated December 2, 2003. These engines are installed on, but not limited to, Bell OH-58D, Bell Helicopter Textron 407, Boeing AH/MH-6M, and MD Helicopters Inc. 600N helicopters.
The FAA is superseding an existing airworthiness directive (AD) for RRC models 250-C30R/3, -C30R/3M, -C47B, and -C47M turboshaft engines. That AD currently requires initial and repetitive electrical signal inspections of the hydromechanical unit (HMU) Power Lever Angle (PLA) potentiometer. This ad continues to require those inspections and adds replacement of the existing HMU with a new design HMU as a mandatory terminating action to the repetitive inspection requirements. This AD results from the manufacturer releasing a redesigned HMU that has a dual-element potentiometer. We are issuing this AD to prevent uncommanded and sudden changes in engine power.
Compliance with this AD is required as indicated, unless already done.
Perform an initial electrical signal inspection of the HMU Power Lever Angle (PLA) potentiometer, within 300 flight hours (FH) after the effective date of this AD. Use paragraphs 2.B. through 2.B.(8) and 2.B.(10) of the Accomplishment Instructions of RRC ACEB No. CEB A-73-3103, Revision 4, dated December 2, 2003; or No. CEB A-73-6030, Revision 4, dated December 2, 2003; to perform the inspection.
(g) Replace the HMU before further flight if the electrical signal inspection result is unacceptable.
Thereafter, perform repetitive electrical signal inspections of the HMU PLA potentiometer within 300 FH of the last inspection. Use paragraphs 2.B. through 2.B.(8) and 2.B.(10) of the Accomplishment Instructions of RRC ACEB No. CEB A-73-3103, Revision 4, dated December 2, 2003; or No. CEB A-73-6030, Revision 4, dated December 2, 2003; to perform the inspection.
(i) Replace the HMU before further flight if the electrical signal inspection result is unacceptable.
Replace the HMU with an HMU that has a P/N not specified in this AD within 600 FH after the effective date of this AD, or January 31, 2005, whichever occurs earlier. Replacing the HMU with an HMU that has a P/N not specified in this AD terminates the repetitive inspection requirement specified in paragraph (h) of this AD.
The aircraft, engines and makers this AD names, by the model designations in its text. A model listed here may still be outside the AD's serial ranges.
Engines
