PRATT & WHITNEY CANADA

SERVICE BULLETIN
P&WC S.B. No. 1755R1

BULLETIN INDEX LOCATOR

72-50-04
TURBOPROP ENGINE
POWER TURBINE SHAFT HOUSING ASSEMBLY, POWER TURBINE STATOR AIR SEAL AND
RETAINING RING - REPLACEMENT OF

MODEL APPLICATION
PT6A-140

Compliance: CATEGORY 7

Summary: Oil may leak through the No. 3 bearing labyrinth seal during engine shutdown.
Replace the PT shaft housing, the PT stator air seal and retaining ring with ones that
have tighter fit, larger surface contact and improved oil drainage capability.

Apr 13/2015 PT6A-72-1755

Revision No. 1: Oct 22/2019 Cover Sheet

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in the grid.

WARNING - PROPRIETARY RIGHTS & EXPORT CONTROLS NOTICE

This bulletin contains proprietary information of Pratt & Whitney Canada Corp. (″P&WC″), which
P&WC provides in confidence and solely for the purposes of supporting engine certification and
providing applicable information regarding the proper use, maintenance, inspection, repair, servicing
and parts application of P&WC products and services, as directed therein. Neither this bulletin nor
any information in it may be disclosed to others, or used for any other purpose, including, without
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Pratt & Whitney Canada Corp.
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Tél. 450-677-9411

22 October 2019

P&WC S.B. No. 1755R1

REVISION TRANSMITTAL SHEET

TURBOPROP ENGINE MODEL PT6A

SUBJECT: Pratt & Whitney Canada Service Bulletin No. PT6A-72-1755, Rev. No. 1, dated Oct
22/2019 (P&WC S.B. No. 1755R1) POWER TURBINE SHAFT HOUSING ASSEMBLY,
POWER TURBINE STATOR AIR SEAL AND RETAINING RING - 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superseded copy.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 service bulletin is revised to change the compliance code from CC6 to CC7 in
Para. 1. E., Planning Information.

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: Apr 13/2015
Revision No. 1: Oct 22/2019
 PRATT & WHITNEY CANADA

SERVICE BULLETIN
P&WC S.B. No. 1755R1
TURBOPROP ENGINE
POWER TURBINE SHAFT HOUSING ASSEMBLY, POWER TURBINE STATOR AIR SEAL AND
RETAINING RING - REPLACEMENT OF

1. Planning Information

A. Effectivity
PT6A-140 Engines which are before and include Serial No. PCE-VA0210.

B. Concurrent Requirements

None.

C. Reason

(1) Problem

Oil may leak through the No. 3 bearing labyrinth seal during engine shutdown.

(2) Cause

The oil drainage is not optimal.

(3) Solution

Replace the PT shaft housing, the PT stator air seal and retaining ring with ones
that have tighter fit, larger surface contact and improved oil drainage capability.

D. Description

Replace the PT shaft housing assembly, PT stator air seal and retaining ring with new
ones.

E. Compliance

CATEGORY 7 - You can do this service bulletin when the supply of superseded parts
is fully used.

F. Approval

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

G. Manpower

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

H. Weight and Balance

The engine weight will increase by 0.11 pounds (0.050 kgs).

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

P&WC No. E7693G, EC-0011076, EC-0012013

P&WC Proprietary Information. Subject to the restrictions on the back of the locator
Apr 13/2015 The export control classification with respect to this document is contained on the back of the locator. PT6A-72-1755
Revision No. 1: Oct 22/2019 © 2015 Pratt & Whitney Canada Corp. Page 1 of 6
PRINTED IN CANADA
 PRATT & WHITNEY CANADA

SERVICE BULLETIN
P&WC S.B. No. 1755R1
TURBOPROP ENGINE
POWER TURBINE SHAFT HOUSING ASSEMBLY, POWER TURBINE STATOR AIR SEAL AND
RETAINING RING - REPLACEMENT OF

1. Planning Information (Cont’d)

I. Electrical Load Data

Not changed.

J. Software Accomplishment Summary

Not applicable.

K. References
Overhaul Manual P/N 3075743 (PT6A-140)
Illustrated Parts Catalog P/N 3075744 (PT6A-140)

L. Publications Affected
Overhaul Manual P/N 3075743 (PT6A-140)
Illustrated Parts Catalog P/N 3075744 (PT6A-140)
CIR3075741

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 $Quote (US, 2015).

The new parts are scheduled to be available Quote.

P&WC Proprietary Information. Subject to the restrictions on the back of the locator
Apr 13/2015 The export control classification with respect to this document is contained on the back of the locator. PT6A-72-1755
Revision No. 1: Oct 22/2019 Page 2 of 6
 PRATT & WHITNEY CANADA

SERVICE BULLETIN
P&WC S.B. No. 1755R1
TURBOPROP ENGINE
POWER TURBINE SHAFT HOUSING ASSEMBLY, POWER TURBINE STATOR AIR SEAL AND
RETAINING RING - REPLACEMENT OF

C. Material Necessary for Each Engine

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

Est. Unit
List Price
($US, Instructions
New P/N Keyword Old P/N Qty 2015) Disposition
3079564-01 Housing, Power Turbine 3059088-01 1 Quote (A)(B)
Shaft, Assembly
3079562-01 Seal, Air, Power Turbine 3076657-01 1 Quote (A)(B)
Stator
ST3397-06 Ring, Retaining ST3397-05 1 Quote (A)(B)
(A) RESTRICTED INTERCHANGEABILITY - (ATA 200 Explanation Code 07):
All parts are interchangeable as a complete set.
(B) Discard the part if it is unserviceable. Return a serviceable part to stock.

D. Reidentified Parts

None.

E. Tooling - Price and Availability

Not applicable.

3. Accomplishment Instructions

A. Remove the parts in the Old P/N list in Para. 2.C., Material Information, in accordance
with the overhaul manual instructions as follows:

v Ref. OHM 72-50-04 POWER TURBINE - DISASSEMBLY.

B. Install the parts in the New P/N list in Para. 2.C., Material Information, in accordance
with the overhaul manual instructions (Ref. Fig. 1) and with the differences shown in
Table 1 and Fig. 2 as follows:

v Ref. OHM 72-50-04 POWER TURBINE - SUB-ASSEMBLY.

C. Write the accomplishment of P&WC S.B. No. 1755 in the engine module log book.

4. Appendix

A. Refer to Figure 2 for fits illustration.

P&WC Proprietary Information. Subject to the restrictions on the back of the locator
Apr 13/2015 The export control classification with respect to this document is contained on the back of the locator. PT6A-72-1755
Revision No. 1: Oct 22/2019 Page 3 of 6
 PRATT & WHITNEY CANADA

SERVICE BULLETIN
P&WC S.B. No. 1755R1
TURBOPROP ENGINE
POWER TURBINE SHAFT HOUSING ASSEMBLY, POWER TURBINE STATOR AIR SEAL AND
RETAINING RING - REPLACEMENT OF

RING, RETAINING
P/N ST3397−05 (PRE−SB)
P/N ST3397−06 (POST−SB)

SEAL, AIR STATOR,

POWER TURBINE
P/N 3076657−01 (PRE−SB)

HOUSING ASSEMBLY,
PT SHAFT
P/N 3059088−01 (PRE−SB)
P/N 3079564−01 (POST−SB)

SEAL, AIR STATOR,

POWER TURBINE
P/N 3079562−01 (POST−SB)

C235343
PT Stator Air Seal - Replacement of
Figure 1

P&WC Proprietary Information. Subject to the restrictions on the back of the locator
Apr 13/2015 The export control classification with respect to this document is contained on the back of the locator. PT6A-72-1755
Revision No. 1: Oct 22/2019 Page 4 of 6
 PRATT & WHITNEY CANADA

SERVICE BULLETIN
P&WC S.B. No. 1755R1
TURBOPROP ENGINE
POWER TURBINE SHAFT HOUSING ASSEMBLY, POWER TURBINE STATOR AIR SEAL AND
RETAINING RING - REPLACEMENT OF

2235

DETAIL A

C235250
Fits Illustration
Figure 2

P&WC Proprietary Information. Subject to the restrictions on the back of the locator
Apr 13/2015 The export control classification with respect to this document is contained on the back of the locator. PT6A-72-1755
Revision No. 1: Oct 22/2019 Page 5 of 6
 PRATT & WHITNEY CANADA

SERVICE BULLETIN
P&WC S.B. No. 1755R1
TURBOPROP ENGINE
POWER TURBINE SHAFT HOUSING ASSEMBLY, POWER TURBINE STATOR AIR SEAL AND
RETAINING RING - REPLACEMENT OF

4. Appendix (Cont’d)

TABLE 1, Table of Limits

Dim. for Ref. Limits

inches (mm) inches (mm)
REF.
NO. IFR Name Min. Max. Min. Max. Replace

Pre-SB1755
2235 Seal-Air, Power 2.2390 2.2400
Turbine Stator (56.871) (56.896)
0.0025 T 0.0005 T
Housing, Power 2.2375 2.2385 (0.064)T (0.013)T
Turbine Shaft, (56.833) (56.858)
Assembly of
Post-SB1755
2235 Seal-Air, Power 2.3870 2.3875
Turbine Stator (60.630) (60.643)
0.0025 T 0.0010 T
Housing, Power 2.3850 2.3860 (0.064)T (0.025)T
Turbine Shaft, (60.579) (60.604)
Assembly of

P&WC Proprietary Information. Subject to the restrictions on the back of the locator
Apr 13/2015 The export control classification with respect to this document is contained on the back of the locator. PT6A-72-1755
Revision No. 1: Oct 22/2019 Page 6 of 6