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250-CZOB CEB-1064250-B17B TP CEB-1043COMMERCIAL ENGINE BULLETIN OverhaulDetroit Diesel AllisonIndianapolis. Indiana 46206

PAGE 1 OF April 25, 197

TURBINE ASSEM BLY, NEW THIRD-STAGE WHEEL ANDPOWER TURBINE SUPPORT OIL SUMP COVER--INSTALLPLANNING INFORMATION:EFFECTIVITY: All 250-C20B Turbine Assem blies prior to S/N CAT 330except S/N CAT 33008 and S/N CAT 33020; all 250-B17BTurbine Assem blies prior to S/N CAT 80032.REASON: To eliminate excessive oil smoke emitting from the eXhauS

ports following shutdownof 250-C20B and 250-B17B enginDESCRIPTION: The exhaust oil smoke emission at engine shutdown isminimized by replacing the C20B/B17B turbine third-stage wheel and the power turbine support oil sumpcover with the C20/B17 turbine third-stage whee l andpower turbine support oil sump cover. This changerestores the No. 7-11 labyrinth seal. Following replac-ment of the third-stage wheel, the power turbine rotorassembly is reidentified.INTERCHANGEABILITY: All changes described in this bulletin must beaccomplished simultaneously.COMPLIANCE: To be accomp lished at first overhaul following partsavailability.APPROVAL:MANPOWER:

FAA-DER ApprovedNo additional man-hours will be required to accomplishthis bulletin at time of overhau l.

MATERIAL AVAILABILITY:Part No. Nomenclature Qty/Assy6887113 Wheel, Turbine Third-Stage 16888547 Cover Assembly, Oil Sump, 1Power Turbine Support

TOOLING: NoneWEIGHT AND BALANCE: Not affected.REFERENCES: CW-1296

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250-C20B CEB-1064250-B17B TP CEB-1043Page 2 OverhaulCOMMERCIAL ENGINE BULLETIN

TURBINE ASSEM BLY, NEW THIRD-STAGE WHEE L ANDPOWER TURBINE SUPPORT OIL SUMP COVER-INSTALL

ACCOMPLISHMENT INSTRUCTIONS:I. At time of turbine overhaul:

A. Replace P/N 688863 3 Turbine Third-stage Wheel with P/N 6887113Wheel.B. Replace P/N 6888626 Power Turbine Support Oil Sump Cover

Assem bly with P/N 6888547 Cover Assemb ly.II. Follow ing incorporation of the P/N 6887113 Third-stage Wheel, thePower Turbine Rotor Assembly is reidentified from P/N 6886447 toP/N 6871483 . The part number is located on the fourth-stage nozzleOD and is applied per AS 478-2Dl or 2E.m. Record compliance with 250-C20B CEB-1064 or 250-B17B TP CEB-1043in the Turbine Assem bly (pink pages) Modification Record, Part III ofthe Engine Log Book.

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250-C20B CEB-1064250-B17B TP CEB-1043Page 3 OverhaulCOMMERCIAL ENGINE BULLETIN

TURBINE ASSEM BLY, NEW THIRD-STAGE WHEE L ANDPOWER TURBINE SUPPORT OIL SUMP COVER-INSTALLMATERIAL AVAILABILITY:New P/N Qty- Nomenclature Old P/x Qty Disposition6871483 1 Rotor Assy, Power Turbine 6886447 1 16887113 1 Wheel, Turbine 3rd Stage 6888633 1 26888547 1 Cover Assembly, Oil Sump, 6888626 1 2Power Turbine Support

Stock Disposition Notes1 Rework and reidentify2 Scrap removed parts on ly

L. 0. DavidsonService ManagerAircraft EnginesMJK/bs c

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