Allison Engine Company
ENGINE CONVERXON, 250-C20B to 250-C2uS
1. PLANNING INFORMATION:
A. Effectivity:
All Model 250-C2OB engines are affected except engines overhauled and
assembled utilizing the turbine alignment fixture P/N 6887818.
B. Reason:
To allow 250-C2OB engines to be converted to 250-C2OS engines at the
discretion of the operator or owner.
C. Description:
Modify and reidentify or replace the following:
Part No. Part No.
250-CZOB 250-C2OS
Engine Assembly 6886440
23005240
23008092
Fuel, Lube & Air 6887052
System 23005241
6887758 to 23008094
6893661
Compressor Assembly 6890550 to 6890560
Compressor Rotor 6876772 to 6890529
Assembly 23005255
Turbine Assembly 6886443 to 23009600
6898735
March 1, 1985
Revision 1 250-C20B, C2OS CEB-1215
November 1, 1988 Page 1 of 9
Rolls-Royce Proprietary Data – Uncontrolled Printed Copy
Allison Engine Company
Commercial Engine Bulletin
1. PLANNING INFORMATION: (Continued)
Part No. Part No.
250-CZOB 250-czos
Gearbox Assembly 6886442
6894171 to 23037417
23004556
Electrical System 6875980 to 23008097
6889081
D. Approval: Technical aspects are FAA approved.
E. Compliance: Comply at operator/owner discretion.
F. Interchangeability:
Use engine model as specified for each aircraft model type certificate
or supplemental type certificate.
G. Material Availability:
NOTES:
(1) Use the current approved parts authorized by the Model 250-CZOS
Illustrated Parts Catalog or authorized superseding parts and the
following:
(2) If a CECO control system is currently installed in the 250-CZOB engine
intended to be converted then it must be re laced by the current
Bendix 250-CZOS control system. Refer to t 1 e operation and mainte-
nance or overhaul manual for removal and replacement procedures for
the control systems.
(3) The following additional parts are required to utilize a P/N 23008021
housing assembly, gearbox power and accessory in the 250-COOS
configuration.
New Part No. Nomenclature LILY
23007219 Plug, Oil Pump-Scavenge Port 1
AS3085-014 Packing 1
6893283 Lead Assembly, Spark Ignitor 1
March 1, 1985
Revision 1 250-CZOB, czos CEB-1215
November 1, 1988 Page 2
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Allison Engine Company
Commercial Engine Bulletin
1. PLANNING INFORMATION: (Continued)
H. Tooling: As required by current 250-CZOS overhaul manual.
I. Weiqht and Balance: Engine weight is increased by 1.90 pounds.
J. Electrical Load Data: Not affected.
K. References: CW3882C, CW4009
(1) 10W2 Operation and Maintenance Manual, Turboshaft Models 250-C20,
-CZOB, -CZOF, -CZOJ
(2) lOW2S Operation and Maintenance Manual, Turboshaft Model 250-C2OS
(3) lOW3 Overhaul Manual Turboshaft Models 250-C20, -C20B, -CZOF, -CZOJ
(41 10W3 Supplement A, Overhaul Manual Supplement, Turboshaft Model
250-C2OS
(51 10W4 Parts Catalog, Turboshaft Models 250-C20, --CZOB, -C2OF, -C2OJ
(6) lOW4S Parts Catalog, Turboshaft Model 250-C2OS
L. Other Publications Affected: None.
M. Prerequisites:
Commercial Engine Bulletin Number Subjects
250-C20 CEB-1072 Compressor, No. 1 Bearing
Seal - Rework
250-C20 CEB-1076 Compressor, Spur Adapter Gearshaft
Bearing Inner F!ace - Add
250-C20 CEB-1088 Compressor, Rear Diffuser Assembly -
Add Bearing Puller Slots
250-C20 CEB-1091 Turbine, Gas Producer Support and
No. 8 Bearing Retaining Plate -
Rework
250-C20 CEB-1100 Compressor, Front Bearing
Housing Assembly - Rework
March 1, 1985
Revision 1 250-C208, C2OS CEB-1215
November 1, 1988 Page 3
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Allison Engine Company
Commercial Engine Bulletin
1. PLANNING INFORMATIW (Continued)
Commercial Engine Bulletin Number Subjects
250-C20 CEB-1110 Compressor, Common 250-C20
and CZOB Configuration -
Modification
250-CZO CEB 1118 Power and Accessory Gearbox, Fuel
Control and Oil Pump Spur Gearshaft
- Rework
250-CZO CEB-1127 Turbine, Power Turbine (N2) Rotor
- Modification
250-C20 CEB-1139 Engine, Compressor No. 1 Bearing Gil
Pressure Reducer - Replace
250-C20 CEB-1158 Engine, Power Turbine Outer
Coupling Nut - Rework
250-C20 CEB-1226 Engine, Accessory Gearbox ASSY
Through Bolt Retention or Idler Gears
250-C20 CEB-1171 Engine, Compressor No. 1 Bearing and
Retaining Nut-Replace
250-C20 CEB-1224 Engine, Turbine Assy, Inner and
Outer Power Turbine Shafts Thicker
Electroless Nickel Plate.
March 1, 1985
Revision 1 250-C208, C2OS CEB-1215
November 1, 1988 Page 4
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Allison Engine Company
Commercial Engine Bulletin
2. Accomplishment Instructions:
A. Modify and reidentify P/N 6886440, P/N 23005240, P/N 6887190, P/N
6893660, or P/N 23004550 Engine Assembly 250-C2OB into P/N 23008092
Engine Assembly 250-C2OS.
(1) Comply with disassembly, inspection, and reassembly procedures in
the appropriate Operation and Maintenance Manual and Overhaul Manual.
(2) Use the Illustrated Parts Catalog for CZOB and C2OS to determine
parts differences between C2OB and C2OS. Remove or modify
applicable 250-C20B parts and add approved 250-C2OS parts to
accomplish conversion.
(a) Modify and reidentify or replace the fuel, lube and air system
P/Ns 6887052, 23005241, 6887758, 6893661 with P/N 23008094 or
superseding part number as follows:
1. Ensure all parts used pass overhaul inspection requirements
and are otherwise in acceptable condition for continued
service use.
1. If P/N's 6887052 or 23005241 Ceco control system is
currently installed on the 250-C2OB engine intended to be
converted, the Ceco system must be replaced with the
current Bendix 250-C2OS control system.
-3. A current 250-C2OB fuel control may be converted to the
250-C2OS configuration. For conversion, return the fuel
control unit to an approved Bendix repair and overhaul
facility
(b) Modify and reidentify or replace compressor assembly P/N
6890550 with P/N 6890560 or superseding part number as follows:
1. Ensure all parts used pass overhaul inspection requirements
and are otherwise in acceptable condition for continued
service use.
1. Reidentify modified compressor assembly by markin new P/N
6876673 blank compressor identification plate wit I? P/N
6890560, Model 250-C2OS and transferring all other data
exactly from old identification plate. Take special care
to transfer serial number accurately.
March 1, 1985
Revision 1 250~C20B, C2OS CEB-1215
November 1, 1988 Page 5
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Allison Engine Company
Commercial Engine Bulletin
2. Accomplishment Instructions: (Continued)
(c) Modify and reidentify the power and accessory gearbox assembly
P/N/Is 6886442, 6894171 or 23004556 to P/N 23037417 as
described below or replace with assembly P/N 23008093.
1. Ensure all parts used pass overhaul inspection requirements
and are otherwise in acceptable condition for continued
service use.
1. If a 250-C20B power and accessory gearbox housing assembly
P/N 23008021 is to be used in the 250-C2OS configuration,
the P/N 23008021 housing may be obtained by reworking P/N
6877181 per CEB-A-1226.
2. Disassemble power and accessory gearbox and remove the
following hardware:
-P/N PART NAME
6853540 Pump Assy, Lub Oil
6844044 Tube Assy, Oil Scav Pickup
6845919 Housing Assy, Filter Lub Oil
689&46 Housing Assy, Filter Lub Oil
4. Install the following hardware:
-P/N PART NAME
6876689 Pump Assy, Lub Oil
23007219 Plug, Oil Pump-Scavenge Pump
AS3085-014 Packing, Preformed O-Ring
6856076 Housing Assy, Filter Lub Oil
23007182 Tube Assy, Scav-Act. Gearbox
6856067 Tube, Oil Transfer
AS3085-012 Packing, Preformed O-Ring
NOTE: P/N 23007219 plug and AS3085-014 O-Ring are installed
in pump prop box scavenge port.
2. Reidentify modified gearbox assembly by marking new P/N
6876675 Identification Plate with new P/N 23037417 and
Model 250-C2OS, and transfering all other data exactly from
old identification plate. Take special care to ensure that
the serial number is accurately transferred.
March 1, 1985
Revision J 250-1X08, C2OS CEB-1215
November 1, 1988 Page 6
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Allison Engine Company
Connnercial Engine Bulletin
2. Accomplishment Instructions: (Continued)
(d) Modify and reidentify or replace turbine assembly P/N 6886443
or 6898735 with P/N 23009600 or superseding part number as
follows:
1. Ensure all parts used pass overhaul inspection requirements
and are otherwise in acceptable condition for continued
service use.
2. P/N 6853511, 6879879 or 6678355 support assy, turbine and
exhaust collector can be modified into P/N 23009596 as
follows:
-a. Remove P/N 23007993 fitting, drain, turbine and exhaust
collector.
b. Cut 0.380 inch diameter plug from Hastelloy X (AMS
5536) sheet stock thickness 0.027 - 0.035 inches
(minimum 0.024 inches after forming) and position over
drain opening.
-c. Weld the 0.380 inch diameter plug in place using weld
rod AMS 5784 or AMS 5782.
-*d Obliterate old part number (so as not to affect the
integrity of the part) and reidentify as P/N 23009596
per AS478-2Dl.
2. Reidentify modified turbine assembly by lnarking new P/N
6876676 blank turbine assembly identification plate with
P/N 23009600, Model 250-C2OS and transferring all other
data exactly from the old identification plate. Take
special care to ensure that the serial number is accur-
ately transferred.
(e) Modify and reidentify or replace P/N 6889081 or 6875980 engine
electrical system assy with P/N 23008097 or superseding part
number.
(31 Reidentify modified engine assembly by marking new P/N 6889365
Identification Plate with New P/N 23004550 and Model 250-C2OS and
transferring all other data exactly from the old identification
plate. Take special care to ensure that serial number is accu-
rately transferred.
B. Record compliance with 250-C20B, C2OS CEB-1215 in the applicable as-
sembly and modification record pages of the engine Log Book.
March 1, 1985
Revision 1 250-UOB, C2OS CEB-1215
November 1, 1988 Page 7
Rolls-Royce Proprietary Data – Uncontrolled Printed Copy
Allison Engine Company
Commercial Engine Bulletin
3. MATERIAL INFORMATION:
A. Basis for quantities is per engine assembly.
5. Bill of material:
Instructions/
New P/N L!Ly Nomenclature Old P/N !L! Disposition
23008092 1 Engine Assy 6886440 1 1
23008092 1 Engine Assy 6887190 1 1
23008092 1 Engine Assy 6893660 1
23008092 1 Engine Assy 23004550 1
23008092 1 Engine Assy 23005240 1 1
23008094 1 * Fuel, Lube & 6887052 1 2
Air System, Engine
23008094 1 - Fuel, Lube & 6887758 1 2
Air System, Engine
23008094 1 . Fuel, Lube & 6893661 1
Air System, Engine
23008094 1 ' Fuel, Lube & 23005241 1 2
Air System, Engine
6890560 1 . Compressor Assy, 6890550 1 2
Axial Centrifugal
6890529 1 - Rotor Assy, 6876772 1 2
Compressor
6890529 1 * Rotor Assy, 23005255 1 2
Compressor
23009600 1 * Turbine Assy, Gas 6886443 1
Producer and Power
23009600 1 - Turbine Assy, Gas 6898735 1
Producer and Power
23008093 1 * Gearbox Assy, 6886442 1
Power & Accessory
March 1, 1985
Revision 1 250-C20B, CZOS CEB-7215
November 1, 1988 Page a
Rolls-Royce Proprietary Data – Uncontrolled Printed Copy
Allison Engine Company
Commercial Engine Bulletin
3. MATERIAL INFORMATION: (Continued1
Instructions/
New P/N !LLY Nomenclature Old P/N Q Disposition
23008093 1 . Gearbox Assy, 6894171 1 1
Power & Accessory
23008093 1 - Gearbox Assy, 23004556 1 1
Power & Accessory
23037417 1 . Gearbox Assy, 6886442 1
Power & Accessory
23037417 1 * Gearbox Assy, 6894171 1
Power & Accessory
23037417 1 - Gearbox Assy, 23004556 1
Power & Accessory
23008097 1 * Electrical 6889081 1
Systems Assy, Engine
23008097 1 * Electrical 6875980 1
Systems Assy, Engine
INSTRUCTIONS/DISPOSITION NOTES:
1. Modify and reidentify.
Modify.
Z: These assemblies consist of a modified CZOB power and accessory gearbox
housing P/N 23008021
PRODUCT SUPPORT
Allison Engine Company
March 1, 1985
Revision 1 250-C20B, CZOS CEB-1215
November 1, 1988 Page 9
Rolls-Royce Proprietary Data – Uncontrolled Printed Copy
