Allison Engine Company

ENGINE, POWER AND ACCESSORY GEARBOX HOUSING ASSEMBLY,

REWORK TO REMOVE WEB WALL MATERIAL FROM CASTING HOUSING.

1. PLANNING INFORMATION:

A. Effectivity:

All Model 250-B15 and -817, (including B17's previously converted to

B17F, C2OS or CZOW) gearbox housing assemblies cast from DP serial
numbered hitchcock castings are affected.

6. Reason:

The webbed partition inadvertently cast during the manufacturing process

could trap contaminates during engine operation.

C. Descriotion:

This modification consist of reworking the gearbox housing and removing

the webbed material by machining the webbed area to a desired dimension.

D. Interchanqeabilitv:

Engines converted from a Model 250-617 to a 250-B17F, 250-C2OS and

250-C2OW could be affected.

E. Compliance:

Compliance 4 To be complied with the next time the affected module or

component is at an authorized repair/overhaul facility and
is disassembled for any reason.

F. Approval:

Technical aspects are F.A.A. approved.

January 25, 1993 250.CZOS, C2OW CEB 1320

250-8156 TP CEB 150
250-817 Series TP CEB 1269
250-B17F Series TP CEB 72-2042
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 Allison Engine Company

Commercial Engine Bulletin

1. PLANNING INFORMATION: (Continued)

G. Material Availability:

New Part No. Nomenclature ClLY w

23056642 Gearbox Housing Assy. 250.B15G

23056647 Gearbox Housing Assy. : 250-B17
23056643 Gearbox Housing Assy. 1 250-817

H. Toolinq:

1. Weiqht and Balance: Not affected

J. Electrical Load Data: Not affected

K. References:

AEM CW 5418

L. Other Publications Affected:

(1) 6W2 Operation and Maintenance Manual, Turboprop Model 250-B15G

(2) 6W3 Overhaul Manual, Turboprop Model 250-B15G

(3) 6W4 Illustrated Parts List, Turboprop Model 250-B15G

(4) llW2 Operation and Maintenance Manual, Turboprop Model 250-817

(5) llW3 Overhaul Manual, Turboprop Model 250-817

(6) llW4 Illustrated Parts List, Turboprop Model 250.B17

(7) GTP 5243-2 Operation and Maintenance Manual, Turboprop Model

250.B17F

(8) GTP 5243-3 Overhaul Manual, Turboprop Model 250-B17F

(9) GTP 5243-4 Illustrated Parts List, Turboprop Model 250.B17F

M. Prerequisites: None.

January 25, 1993 250-C2OS, C2OW CEB 1320

250-8156 TP CEB 150
250-817 Series TP CEB 1269
250-B17F Series TP CEB 72-2042
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 Allison Engine Company
Commercial Engine Bulletin

2. ACCOMPLISHMENT INSTRUCTIONS:

A. Remove/disassemble the accessory gearbox as specif~ied in the appropriate

Operation and Maintenance Manual/Overhaul Manual.

B. Comply with appropriate removal, disassembly, cleaning, inspection,

removal of coating, plating, assembly and installation procedures in the
applicable overhaul manual.

C. Modify and reidentify the accessory gearbox housing as follows:

(1) Ensure all parts to be modified or reinstalled are in serviceable

condition for continued use or restorable as defined by the
applicable Overhaul Manual and this bulletin.

(2) Modify housing by first identifying View "A" in Figure 1.

(3) Remove the appropriate amount of stock by machining to the desired

dimensions listed in Figure 2.

(4) Recoat the machined surface as specified in the appropriate Overhaul

Manual.

(5) Inspect Part in accordance with dimensions listed in Figure 2.

D. Reidentify the reworked gearbox housing by obliterating the old P/N (so
as not to affect the integrity of the part) and adding the new P/N per
AS 478-ZDI.

E. Record compliance with this Bulletin in the Engine Log Book (White
Pages), and Gearbox Assembly (Yellow Pages) part III, Modification
Record as applicable with the following bulletins:

250-CZOS, CZOW CEB 1320

250-B15G Series TP CEB 150
250-817 Series TP CEB 1269
250-B17F Series TP CEB 72-2042

January 25, 1993 250-CZOS, C2OW CEB 1320

250.BISG TP CEB 150
250-817 Series TP CEB 1269
250.B17F Series TP CEB 72-2042
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 Allison Engine Company

Commercial Engine Bulletin

2. ACCOMPLISHMENT INSTRUCTIONS: (continued)

Gearbox Housing Assembly

Figure fl

January 25, 1993

250-C2OS, C2OW CEB 1320
250.B15G TP CEB 150
250-817 Series TP CEB 1269
250.B17F Series TP CEB 72-2042
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 Allison Engine Company

Commercial Engine Bulletin

2. ACCOMPLISHMENT INSTRUCTIONS: (continued)

EARBOX HOUSING OIL FILTER HOUSING

SPLITLINE SPLITLINE

F/ LAP ?/

VIEW A

Gearbox Housing Assembly

Figure #2

January 25, 1993 250-CZOS, C2OW CEB 1320

250-Bl5G TP CEB 150
250-817 Series TP CEB 1269
250.B17F Series TP CEB 72-2042
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 Commercial Engine Bulletin

3. MATERIAL INFORMATION:

A. Basis for quantities is per gearbox assembly.

B. Bill of material:

Instructions/
New P/N QQ Nomenclature Old P/N QQ Disposition

23056642 1 Gearbox Housing 6577714 1 1

Assy.
23056647 1 Gearbox Housing 6877171 1 1
Assy.
23056643 1 Gearbox Housing 23054606 1 1
Assy.

INSTRUCTIONS/DISPOSITION NOTES:

1. Rework and Reidentify.

CUSTOMER SUPPORT
Allison Engine Company

January 25, 1993 250.C205, CZOW CEB 1320

250-B15G TP CEB 150
250.B17 Series TP CEB 1269
250-817F Series TP CEB 72-2042
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