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AD/AL 250/84 - HMU PLA Potentiometer
Allison Turbine Engines - 250 SeriesAllison Turbine Engines - 250 Series
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Allison Turbine Engines - 250 Series
| AD/AL 250/84 | HMU PLA Potentiometer | 2/2005 |
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| Applicability: | 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 paragraph 1.A. Group A of RRC Alert Commercial Engine Bulletins (ACEB) CEB A-73-3103, Revision 4, dated 2 December 2003 and CEB A-73-6030, Revision 4, dated 2 December 2003. |
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| Note 1: These engines are known to be installed on, but not limited to, Bell OH-58D, Bell Helicopter Textron 407, Boeing AH/MH-6M and MD Helicopters Inc. 600N helicopters. | |
| Requirement: | 1. Perform an electrical signal inspection of the HMU Power Lever Angle (PLA) potentiometer in accordance with paragraphs 2.B. through 2.B.(8) and 2.B.(10) of the Accomplishment Instructions of ACEB CEB A-73-3103, Revision 4, or CEB A- 73-6030, Revision 4. |
| 2. If the electrical signal result is found to be unacceptable during the Requirement 1 inspection replace the HMU. | |
| 3. Replace the HMU with a redesigned HMU (ie one with a dual element potentiometer) that has a P/N that is not listed in paragraph 1.A. Group A of ACEB CEB A-73-3103, Revision 4 and CEB A-73-6030, Revision 4. Replacing the HMU with an HMU that has a P/N not specified in the referenced ACEBs terminates the Requirement 1 repetitive inspection. | |
| Note 2: FAA AD 2004-24-04 Amdt 39-13880 refers. | |
| Compliance: | For Requirements 1 - Within 300 time in service (TIS) after the effective date of this Directive or within 300 hours TIS after completing the inspection in accordance with Requirement 1 of AD/AL 502, which ever occurs earlier, and thereafter at intervals of 300 hours TIS until Requirement 3 is accomplished. |
| For Requirement 2 - Before further flight immediately following the Requirement 1 inspection. | |
| For Requirement 3 - Within 600 hours TIS after the effective date of this Directive, or by 17 March 2005, whichever occurs earlier. |