S.I.L NO. PT6A-213

SERVICE INFORMATION LETTER

This Service Information Letter is valid until superseded or cancelled by revision.

EXPORT CONTROL CLASSIFICATION: This document does not contain technical data.ISSUED: Oct 16/2013 Page 1 of 2

PRATT & WHITNEY CANADA CORP.MARIE-VICTORIN, LONGUEUIL

QUEBEC, CANADA J4G 1A1PRINTED IN CANADA

Subject Compressor Inlet Case Corrosion

Applicability P/N 3114545-01 installed on PT6A-64, PT6A-66, PT6A-66B and PT6A-66D

P/N 3074675-01 installed on PT6A-67B

P/N 3070318-01 installed on PT6A-67P

Reference Engine Maintenance Manual (EMM)Service Information Letter (SIL) PT6A-206FAA Advisory Circular AC 43-4A “Corrosion Control for Aircraft”CSPN 1007015 applicable to PT6A-64/66/66B/66DCSPN 1006564 applicable to PT6A-67B/67P

P&WC has received reports that inlet cases on some engine models were found with corrosion (Ref.figure 1 and 2). It is important that the corrosion be identified in the early stages so that it can berepaired to reduce the likelihood of corrosion progressing beyond repairable limits. Therefore, we havereviewed our EMM recommendation to better assess and prevent corrosion propagation. Per theP&WC Warranty Policy, corrosion and sulphidation damage are not covered. However, consideringthese new recommendations we are introducing a commercial support program for the PT6A-64/66/66B/66D1 and the existing PT6A-67P2 program is being revised to include the 67B model, whichcovers in-situ repair made in accordance with the following EMM revisions:

New Annual Inlet case periodic Inspection TaskA new annual task to verify presence of corrosion on the inlet case was added. Refer to P&WCEMM section 72-00-00, INSPECTION, Periodic Inspection. Inspection can be done with the inletscreen removed or alternatively with Borescope. If corrosion is within repairable limits, theengine can be returned to service for a period of time as specified in the EMM, for the purposeof scheduling the repair in accordance with EMM section 72-20-00 Para. 8. A. The corrosionprogression in salt laden area must be considered.

New Annual Corrosion Inhibitor ApplicationMagnesium components such as the inlet case may be susceptible to corrosion. It is importantto wash the engine intake area to remove any salt deposits (as applicable ref. FAA AdvisoryCircular AC 43-4A) and to periodically apply corrosion inhibitors per P&WC EMM. It isrecommended that all pilots, owners and maintenance personnel involved with the operationand maintenance of PT6A engines be familiar with these recommendations which are found inthe EMM section 71-00-00. P&WC has approved a number of corrosion inhibitors that may beapplied periodically and will be part of the annual inspection recommendation. Refer to EMMsection 72-00-00 for application instructions and approved product listing. Corrosion X™inhibiter has shown good results on the PT6A Large series engines due to its effectiveness athigher oil/case temperatures.

PRATT & WHITNEY CANADASERVICE INFORMATION LETTER

P&WC: S.I.L NO. PT6A-213

EXPORT CONTROL CLASSIFICATION: This document does not contain technical data.ISSUED: Oct 16/2013 Page 2

New In-Situ Repair procedure and revised Repair LimitsInstructions on how to repair the inlet case can be found in P&WC EMM section 72-20-00Compressor Inlet Case – Maintenance Practices.

o New Alodine pen kit added to ease application.o Expanded Allowable corrosion depth & surface limits, except for specific areas.

Figure 1 Figure 2Example of surface corrosion Example of surface corrosion

In the eventuality that the case is beyond repairable limits and requires replacement at or before 1stOverhaul, P&WC is offering a new Inlet casing at a preferred discount (A-64/66/66B/66D1) (A-67B/67P2). The P&WC Local Field Support Representative or P&WC Customer First Center should becontacted should you become aware of an engine showing evidence of inlet case corrosion beyondreparable limits.

For further information, please contact your local P&WC Field Support Representative, or the P&WCCustomer First Center, Tel +1 450-647-8000 or +1-800-268-8000. We can also be reached atcfirst@pwc.ca, or our website www.pwc.ca.

PRATT & WHITNEY CANADA CORP.

Jeremy GanivetPT6A Customer ManagerCustomer Service

1CSPN 1007015 applicable to PT6A-64/66/66B/66D

2CSPN 1006564 applicable to PT6A-67B/67P