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ALERT

SUBJECT:PURPOSE:

EFFECTIVITY:

COMPLIANCE:

BACKLASHCHECK:

DUAL ELEMENT FUEL PUMP DRIVE SHAFT INSPECTIONSome operators have reported excessive spline wear on dualelement fuel pump drive shafts. This CSL, therefore, intendsto assure satisfactory pump operation tly having operators checkdrive shaft backlash each 200 hours. It describes (1) a quickmethod to externally check spline wear, (211 if required, aprocedure to determine spline wear and (3) replacementinstructions for shafts with spline wear beyond 0.004 inch.All 250 series dual element fuel pumps: P/N 6854292, 6857548,6877719, 6856250, and 6876803.NOTE: P/N 6851555, 6851557, 6895181 and 6895190 pumps do not

require this inspection. The pumps incorporate themuff spline adapter per CEB-A-161 l(C18) or CEB-A-1051(C20) which greatly reduces spline wear.

Check fuel pump drive shaft backlash ta' assure satisfactorypump operation until next overhaul as follows:1. New and overhauled pumps - check at 200 hours (or within 25

hours if 200 hours have elapsed) and repeat check at200-hour intervals until next overhaul.2. If the drive and shouldered shafts are replaced, re-check

at accrual of next 200 hours and repeat check at 200-hourintervals until next overhaul.NOTE: Pumps must be modified to incorporate the new muff

spline adapter per CEB-A-161 or CEB-A-1051 at nextoverhaul or whenever the pump is returned to anoverhaul facili ty for any reason, whichever comesfirst.

1. Remove dual element fuel pump from engjine per theapplicable 250 Operation and Maintenance Manual.

November 16, 1972Revision No. 4September 1, 1994

250.Cl8 Series250-C2O/C2OB Series

CSL-61CSL-1007Page 1 of 11

Rolls-Royce Proprietary Data Uncontrolled Printed Copy

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ALLISON ENGINE COMPANYCommercial Service Letter

2. Cut out template (Figure 1). Paste template on 5 x 8.in.index card or cardboard; cut out 1.5 in. dia circle.

3. Place template around fuel pump thrust plate as shown inFigure 2.4. Bend a paper clip or piece of lockwire to fit between the

splines on the shouldered shaft to serve as a pointer (seeFigure 3). Install paper clip on shaft.

5. Turn the shouldered shaft against the left stop. Align thetemplate centerline with the pointer (Figure 4).

6. Turn the shouldered shaft in the opposite direction tocheck drive shaft backlash.a. If the pointer is within the IO'-degree range (Figure

5), reinstall the pump and run the engine and check forleaks. (Refer to the applicable 250 Operation andMaintenance Manual.)

b. If the pointer is outside the IO--degree range,visual ly inspect the drive shaft splines to determinethe wear step.

SPLINE 1. Remove five M60GS632-6C Self-locking Screws andINSPECTION: P/N 02-12933 Thrust Plate from Cover and Housing Assembly

(Figure 6).2. Remove P/N 797-21 Spring (Figure 7).3. Remove P/N 02-15097 Shouldered Shaft (Figure 8). Do not

remove P/N 102-713 Diaphragm, P/N 02-12922 Diaphragm Guide,P/N 02-12934 Wobble Washer, P/N 02-12932 Stop, and P/N99-330 Washer from the shouldered shaft.

4. Remove P/N 99-4226 Spring and P/N 02-14623 Spacer (Figure9).

5. Remove P/N 02-14622 Drive Shaft (Figure IO).CAUTION: DO NOT ROTATE THE DRIVE SHAFT DURING REMOVAL.


250-Cl8 Series250-C20/C20B Series

CSL-61CSL-1007

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6. Run your finger nail or suitab~ ie pointed object across theworn spline surface (Figure 11). Reject the drive shaft ifyour finger nail or pointed object catches on the wearstep. If you have any doubts whether spline wear isacceptable, compare the wear step with a 0.004-in. feelergage. Reject the drive shaft and shouldered shaft if driveshaft wear step is greater than 0.004 inch.

DRIVE SHAFT 1. Install an acceptable or new P/N OS14622 DriveINSTALLATION: Shaft as follows:

2.3.

4.5.


a. Before an acceptable drive shaft is reinstalled , alignthe shaft match marks with the outer drive gear matchmarks. Then insta ll the drive sha~ft (Figure 10).

b. During a new shaft installation, it may be necessary tosliohtlv turn the pump outer drive gear in eitherdirection. The relationship between the forward (long)and aft (short) spline s on the drive shaft is optional,i.e., they do not line up.(1) Visually, compare the new shaft short sp lines and

rejected shaft spline s with re:spect to the longsplines to determine direction of rotation.

(2) For example, if the short splines on the new shaftare located further to the right (CW) than shortsplines on the rejected shaft, sligh tly turn thenew shaft and outer drive gear CCW until the shortsplines mesh with the inner drive gear. If theshort splines are further to the left (CCW ), turnthe new shaft CW.

(3) Since the pump drive gears are spring-loaded, it iseasier to rotate the pump outer gear with theshouldered shaft insta lled on the drive shaft.

Install P/N 02-14623 Spacer around drive shaft (Fig. 9).Place P/N 99-4226 Spring into an acceptable or new P/N02-15097 Shouldered Shaft (Figure 12). Then insta llShouldered Shaft, P/N 102-713 Diaphragm, P/N 02-12922Diaphragm Guide, P/N 02-12934 Wobble Washer, P/N 02-12932Stop, and P/N 99-330 Washer as an assembly over the DriveShaft.Install P/N 797-21 Spring (Figure 7).Install P/N 02-12933 Thrust Plate and five M60GS632-6CSelf-locking Screws (Figure 6). Tighten screws 15-18 lb.in.

250-Cl8 Series250.C2O/C2OB Series



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6. Install pump and check run the engine. Monitor themeasured gas temperature (TOT). If the TOT limit s areexceeded, perform the required maintenance action andremove the fuel pump and return to overhaul. (Refer toapplicable 250 Operation and Maintenance Manual).

7. Record compliance with 250.CSL-A-61 (C18) or 2%CSL-A-1007(CZO) in the Engine Assembly (white pages) InspectionRecord, Part III of the Engine Log Book.

APPROVAL: Technical Aspects are FAA Approved. The accomplishmentinstructions of Revision 3 or Revision 4 to this Bulletin areapproved by the Manager, Chicago Aircra ft Certification Office forcompliance with AD 78-14-08 as indicated.

CUSTOMER SUPPORTALLISON ENGINE COMPANY


250.Cl8 Series250-C20/CZOB Series



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I---- --

I

-----___

_-L/ \/ \(i, \\I- -

- CUT OUT 1.5-IN.DIAMETER CIRCLE

------1IIIII

I

I

IIIIIIII

I II II III-----------------_-_-_-_ 1


DRIVE SHAFT BACKLASH CHECK TEMPLATEFigure 1

250-Cl8 Series250-C2O/C2OB Series CSL-61CSL-1007

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i

BACKLASH TEMPLATE INSTALLED ON FUEL PUMPFigure 2

BACKLASH POINTER INSTALLED ON SHOULDERED SHAFTFigure 3


250.Cl8 Series250.CZO/C2OB Series



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-TEMPLATE CENTERLINE ALIGNED WITH POINTER

Figure 4


CHECKING BACKLASHFigure 5

250.Cl8 Series250-C20/C20B Series

CSL-61CSL-1007

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DUAL ELEMENT FUEL PUMPFigure 6

,.:.,__---


Figure 7250-Cl8 Series250-C2O/C206 Series

CSL-61CSL-1007

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REMOVING SHOULDERED SHAFT, DIAPHRAGM, DIAPHRAGMGUIDE, STOP, AND WASHER

Figure 8


Figure 9250.Cl8 Series250.CZO/C2OB Series CSL-61CSL-1007

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REMOVING/INSTALLING DRIVE SHAFTFigure 10

November 16, 1972Revision No. 4Set&ember 1, 1994

CHECKING WEAR STEPFigure 11

250-Cl8 Series250.C20/C20B Series

CSL-61CSL-1007

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INSTALLING P/N 99-4226 SPRING INTOP/N 02-15097 SHOULDER SHAFT

Figure 12250.Cl8 Series250.C2O/C2OB Series


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Csl 1007