BULLETIN INDEX LOCATOR

49-21-02

AUXILIARY POWER UNIT

EXHAUST DUCT SUPPORT AND INSULATION BLANKETS - REPLACEMENT OF

MODEL APPLICATION

PW901A

Compliance: CATEGORY 3

Summary: Modify the rear gas generator case, exhaust duct support, and the turbine exhaust

duct flanges and introduce additional flange retaining hardware to prevent potential

flange separation in conditions of extreme distress.

PRATT & WHITNEY CANADA

ALERT SERVICE BULLETIN

P&WC S.B. No. A16255R2

Dec 12/2007 3910001-49-A16255

Revision No. 2: Mar 01/2011 Cover Sheet

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Quebec J4G 1A1.
REVISION TRANSMITTAL SHEET

AUXILIARY POWER UNIT MODEL PW900

SUBJECT: Pratt & Whitney Canada Service Bulletin No. 3910001-49-A16255, Rev. No. 2, dated

Mar 01/2011 (P&WC S.B. No. A16255R2) EXHAUST DUCT SUPPORT AND

INSULATION BLANKETS - REPLACEMENT OF

Replace your existing copy of this service bulletin with the attached revised bulletin. Destroy the

superseded copy.

Please retain this Revision Transmittal Sheet with the revised bulletin.

SUMMARY: This revision is being issued to change the compliance code from 4 to 3 and to

update pricing to 2011 catalog pricing.

EFFECT OF REVISION ON PRIOR ACCOMPLISHMENT:

None.

NOTE: A black bar in the left margin indicates a change in that line of text or figure.

REVISION HISTORY:

Original Issue: Dec 12/2007

Revision No. 1: Sep 12/2008

Revision No. 2: Mar 01/2011

Pratt & Whitney Canada Corp.

1000, Marie-Victorin

Longueuil, Québec, Canada J4G 1A1

Tél. 450-677-9411

01 March 2011

P&WC S.B. No. A16255R2

1. Planning Information

A. Effectivity

PW901A Engines which are before and include Serial No. PCE-900776.

B. Concurrent Requirements

None.

C. Reason

(1) Problem

The rear gas generator case, exhaust duct support, and the turbine exhaust duct

can separate at their flanges in conditions of extreme distress.

(2) Cause

The strength of the current flange and attaching bolt design can be improved to

prevent flange separation at all distress conditions.

(3) Solution

Introduce flange retainer segments, a mating spacer ring, and an additional bolt

and nut arrangement to strengthen a redefined flange design. The flange redesign

makes it necessary to introduce new rear gas generator and exhaust duct

insulation blanket segments.

D. Description

Remove and replace the exhaust duct support, exhaust duct insulation blankets, and the

rear gas generator case insulation blankets.

E. Compliance

CATEGORY 3 - P&WC recommends to do this service bulletin the first time the engine

or module is at a maintenance facility than can do the procedures,

regardless of the scheduled maintenance action or reason for engine

removal prior to June 1, 2015.

F. Approval

D.O.T./D.A.A. approved.

G. Manpower

No more man-hours are necessary to include this service bulletin at overhaul.

P&WC No. D7219B, D7219G, D7219G/1

PRATT & WHITNEY CANADA

ALERT SERVICE BULLETIN

P&WC S.B. No. A16255R2

P&WC Proprietary Information. Subject to the restrictions on the back of the locator.

Dec 12/2007 3910001-49-A16255

Revision No. 2: Mar 01/2011 Page 1 of 12 © 2007 Pratt & Whitney Canada Corp.

PRINTED IN CANADA

AUXILIARY POWER UNIT

EXHAUST DUCT SUPPORT AND INSULATION BLANKETS - REPLACEMENT OF
1. Planning Information (Cont’d)

H. Weight and Balance

The engine weight will increase by 3.05 pounds (1.38 kgs).

The effect of weight change on the center of gravity is negligible.

I. Electrical Load Data

Not changed.

J. Software Accomplishment Summary

Not applicable.

K. References

Component Maintenance Manual P/N 3900283 (PW901A)

L. Publications Affected

Component Maintenance Manual P/N 3900283 (PW901A)

Illustrated Parts Catalog P/N 3900282 (PW901A)

M. Interchangeability and Intermixability of Parts

Interchangeability - Refer to Para. 2.C

Intermixability - Not changed.

2. Material Information

A. Industry Support Information

Not applicable.

B. Material - Cost and Availability

You can get the procurable parts listed in Para. 2.C. from any Pratt & Whitney Canada

Parts Distribution Center.

The estimated total cost of new parts needed to replace old parts is $39668.70 (US, 2011).

The new parts are available.

PRATT & WHITNEY CANADA

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P&WC S.B. No. A16255R2

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Dec 12/2007 3910001-49-A16255

Revision No. 2: Mar 01/2011 Page 2 of 12

AUXILIARY POWER UNIT

EXHAUST DUCT SUPPORT AND INSULATION BLANKETS - REPLACEMENT OF
C. Material Necessary for Each APU

The quantity of materials listed in this section is on a per APU basis.

New P/N Keyword Old P/N Qty

Est. Unit

NET Price

($US,

2011)

Instructions

Disposition

Exhaust Duct Support and Mounting Hardware:

3902607-01 Support Assy, Exhaust Duct 3910323-01 1 12714.00 (A)(B)

Ê Insert, Flange Jacking 3101309-01 7 (A)

ST3287-01 Ê Insert, Flange Jacking 4 44.21 (A)

MS9696-08 Bolt, Machine, Dbl Hex ST3860-19 24 10.63 (A)

Washer, Flat MS9321-09 24 (A)

Spacer, Sleeve 3900940-01 24 (A)(B)

3902643-01 Ring, Spacer Assy 1 5794.20 (A)

3902604-01 Ê Ring, Spacer 1 NP (A)

ST3020-010 Ê Pin, Shouldered, Headless 1 43.55 (A)

3902606-01 Retainer Segment 3 4740.00 (A)

MS9697-14 Bolt, Mach, Dbl Hex 23 20.16 (A)

AS3554-10 Nut, Self-Locking, Dbl Hex 23 60.30 (A)

Insulation Blankets for the Rear Gas Generator Case:

3902611-01 Blanket Segment,

Insulation, Gas Generator,

Rear

3911319-01 1 1525.80 (A)

3902612-01 Blanket Segment,

Insulation, Gas Generator,

Rear

3911076-01 1 892.20 (A)

Insulation Blankets for the Turbine Exhaust Duct:

3902613-01 Blanket Segment,

Insulation, Exhaust Duct

3910309-01 1 1208.40 (A)

3902614-01 Blanket Segment,

Insulation, Exhaust Duct

3910308-01 1 1208.40 (A)

PRATT & WHITNEY CANADA

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P&WC S.B. No. A16255R2

P&WC Proprietary Information. Subject to the restrictions on the back of the locator.

Dec 12/2007 3910001-49-A16255

Revision No. 2: Mar 01/2011 Page 3 of 12

AUXILIARY POWER UNIT

EXHAUST DUCT SUPPORT AND INSULATION BLANKETS - REPLACEMENT OF
New P/N Keyword Old P/N Qty

Est. Unit

NET Price

($US,

2011)

Instructions

Disposition

(A) RESTRICTED INTERCHANGEABILITY - (ATA 200 Explanation Code 07):

All the old parts must be replaced by all the new parts as an assembly.

(B) Discard. Do not use again in any application.

D. Reidentified Parts

None.

E. Tooling - Price and Availability

Tool No. Nomenclature

Est. Price

($US,) Delivery

PWC30114-61 Wrench

PWC64241-3 Alignment Pin

3. Accomplishment Instructions

A. Remove the parts listed under Old P/N in Para. 2.C., Material Information, per the

applicable component maintenance manual instructions.

B. Install the parts listed under New P/N in Para. 2.C., Material Information, per the

applicable component maintenance manual instructions except for the differences that

follow:

NOTE: During the assembly of this new configuration, the turbine exhaust duct is

installed on the rear gas generator case before the exhaust duct support.

(1) Install the spacer ring assembly P/N 3902643-01 as follows (Ref. Fig. 1):

(a) With a (PWC05-018B) blue marking pencil, put an X mark on the spacer ring

assembly in line with the offset hole (Ref. View A).

(b) Put the spacer ring assembly in an oven at 250 to 300 °F (121-149 °C) for 15

minutes minimum.

(c) Install the two (PWC64241-3) alignment pins on the rear gas generator case.

(d) Remove the spacer ring assembly from the oven, and install it on the rear gas

generator case with the X mark at BDC facing out.

(2) Install the turbine exhaust duct as follows:

PRATT & WHITNEY CANADA

ALERT SERVICE BULLETIN

P&WC S.B. No. A16255R2

P&WC Proprietary Information. Subject to the restrictions on the back of the locator.

Dec 12/2007 3910001-49-A16255

Revision No. 2: Mar 01/2011 Page 4 of 12

AUXILIARY POWER UNIT

EXHAUST DUCT SUPPORT AND INSULATION BLANKETS - REPLACEMENT OF
3. Accomplishment Instructions (Cont’d)

(a) Apply (PWC06-011) assembly fluid to the No. 4 bearing rollers inside the rear

gas generator case, to load the rollers inward to make sure they will clear the

carbon seal when the turbine exhaust duct is installed (Ref. Section D-D).

CAUTION: LOWER THE TURBINE EXHAUST DUCT CAREFULLY INTO THE

REAR GAS GENERATOR CASE TO AVOID DAMAGE TO THE NO. 4

BEARING CARBON SEAL.

(b) With the turbine exhaust duct pre-assembled per the applicable component

maintenance manual instructions, align the offset hole on the turbine exhaust

duct with the offset hole at BDC on the spacer ring assembly P/N 3902643-01,

and install the turbine exhaust duct (Ref. Views A and B).

(c) Remove the two (PWC64241-3) guide pins from the rear gas generator case.

(d) Apply (PWC03-001) engine oil on the threads of the 24 bolts P/N MS9696-08.

(e) Install the 24 bolts to attach the turbine exhaust duct and spacer ring

assembly P/N 3902643-01 to the rear gas generator case.

(f) Torque the 24 bolts in a star pattern 36 to 40 lbf.in. (4.0-4.5 Nm).

(3) Install the exhaust duct support P/N 3902607-01 and three retainer segments

P/N 3902606-01 as follows:

(a) Align the X mark on the exhaust duct support with the shouldered pin on the

spacer ring assembly P/N 3902643-01, and install the exhaust duct support

(Ref. View E).

(b) Apply (PWC03-001) engine oil on the threads of the 23 bolts P/N MS9697-14.

(c) Install the three retainer segments on the forward side of the spacer ring

assembly P/N 3902643-01, starting with the large slot in the middle of a retainer

segment aligned with the offset hole at BDC, with the 23 bolts and self-locking

nuts P/N AS3554-10 finger tight (Ref. View F).

(d) Measure the gap all around between the three retainer segments and the rear

gas generator case and make sure the gap is per F&C Ref. No. 1830 (Ref.

Fig. 2, Section H-H).

(e) Use the (PWC30114-61) wrench to hold the 23 self-locking nuts and torque the

23 bolts in a star pattern 85 to 95 lbf.in. (9.6-10.7 Nm) (Ref. Fig. 1).

(f) Measure the gap again all around between the three retainer segments and the

rear gas generator case and make sure the gap is per F&C Ref. No. 1830

(Ref. Fig. 2, Section H-H).

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P&WC S.B. No. A16255R2

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Dec 12/2007 3910001-49-A16255

Revision No. 2: Mar 01/2011 Page 5 of 12

AUXILIARY POWER UNIT

EXHAUST DUCT SUPPORT AND INSULATION BLANKETS - REPLACEMENT OF
3. Accomplishment Instructions (Cont’d)

C. Write accomplishment of P&WC S.B. No. 16255 in the APU log book.

4. Appendix

A. Refer to Table 1 and Figure 2 for the changes to the fits and clearances.

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Dec 12/2007 3910001-49-A16255

Revision No. 2: Mar 01/2011 Page 6 of 12

AUXILIARY POWER UNIT

EXHAUST DUCT SUPPORT AND INSULATION BLANKETS - REPLACEMENT OF
RETAINER SEGMENT (QTY. 3)

P/N 3902606−01

SELF−LOCKING NUT (QTY. 23)

P/N AS3554−10

SPACER RING ASSY.

P/N 3902643−01

REAR GAS GENERATOR

CASE (REF.)

TURBINE EXHAUST

DUCT (REF.)

BOLT (QTY. 23)

P/N MS9697−14

EXHAUST DUCT SUPPORT

P/N 3902607−01

BOLT (QTY. 24)

P/N MS9696−08

C

A B

ALIGNMENT PIN

PWC64241−3

C127892

Exhaust Duct Support - Installation of

Figure 1 (Sheet 1 of 3)

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AUXILIARY POWER UNIT

EXHAUST DUCT SUPPORT AND INSULATION BLANKETS - REPLACEMENT OF
VIEW A

BDC

X

OFFSET

HOLE

VIEW C

E

(SHOWN ASSEMBLED)

D D

F

VIEW B SECTION D−D

OFFSET

HOLE

No. 4 BEARING

ROLLERS (REF.)

TURBINE EXHAUST

DUCT (REF.)

X MARK SHOULDER PIN

P/N ST3020−010

SPACER RING ASSY.

P/N 3902643−01

C127893

Exhaust Duct Support - Installation of

Figure 1 (Sheet 2)

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EXHAUST DUCT SUPPORT AND INSULATION BLANKETS - REPLACEMENT OF
VIEW F

VIEW E

LARGE SLOT

RETAINER SEGMENT

P/N 3902606−01

X

SHOULDER PIN

P/N ST3020−010

X MARK

EXHAUST DUCT SUPPORT

P/N 3902607−01

C127894

Exhaust Duct Support - Installation of

Figure 1 (Sheet 3)

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AUXILIARY POWER UNIT

EXHAUST DUCT SUPPORT AND INSULATION BLANKETS - REPLACEMENT OF
4. Appendix (Cont’d)

TABLE 1, Changes to the Fits and Clearances

Dim. for Ref.

inches (mm)

Limits

inches (mm) REF.

NO. IFR Name Min. Max. Min. Max. Replace

Pre-SB

1190 C Duct-Turbine Exhaust,

Assy of

15.528

(394.411)

15.530

(394.462) 0.012 0.018

Support-Exhaust Duct, (0.305) (0.457)

Assy of

15.542

(394.767)

15.546

(394.868)

Post-SB

1190 C Duct-Turbine Exhaust,

Assy of

15.528

(394.411)

15.530

(394.462) 0.012 0.018

Ring-Spacer, Assy of 15.542 (0.305) (0.457)

(394.767)

15.546

(394.868)

Pre-SB

1192 B Case-Gas Generator

Rear, Assy of

16.478

(418.541)

16.480

(418.592) 0.020T 0.016T

Support-Exhaust Duct, (0.508T) (0.406T)

Assy of

16.460

(418.084)

16.462

(418.135)

Post-SB

1192 C Case-Gas Generator

Rear, Assy of

16.478

(418.541)

16.480

(418.592) 0.020T 0.016T

Ring-Spacer, Assy of 16.460 (0.508T) (0.406T)

(418.084)

16.462

(418.135)

Post-SB

1281 C Pin-Shouldered,

Headless

0.0620

(1.575)

0.0621

(1.577) 0.0000 0.0011T

Ring-Spacer, Assy of 0.0610 (0.000) (0.028T)

(1.549)

0.0620

(1.575)

Post-SB

1282 C Pin-Shouldered,

Headless

0.0773

(1.962)

0.0778

(1.975) 0.0013 0.0058

Support-Exhaust Duct, (0.032) (0.146)

Assy of

0.0790

(2.007)

0.0830

(2.108)

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AUXILIARY POWER UNIT

EXHAUST DUCT SUPPORT AND INSULATION BLANKETS - REPLACEMENT OF
4. Appendix (Cont’d)

TABLE 1, Changes to the Fits and Clearances (Cont’d)

Dim. for Ref.

inches (mm)

Limits

inches (mm) REF.

NO. IFR Name Min. Max. Min. Max. Replace

Post-SB

1283 C Ring-Spacer, Assy of 17.178

(436.321)

17.182

(436.423) 0.012 0.018

Support-Exhaust Duct, (0.305) (0.457)

Assy of

17.194

(436.728)

17.196

(436.778)

Post-SB

1830 C Minimum gap 0.010 in.

(0.254 mm) between

retainer segment and

gas generator case all

around.

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EXHAUST DUCT SUPPORT AND INSULATION BLANKETS - REPLACEMENT OF
G

J

VIEW G

VIEW J

SECTION H−H

SECTION K−K

H

H

K

K

L

DETAIL L

1830

1283

1282

1281

1190

1192

SPACER RING

ASSEMBLY

P/N 3902643−01

REAR

GAS GENERATOR

CASE

(REF.)

C127896

Changes to the Fits and Clearances

Figure 2

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