Civil Aviation Safety Alert (CASA) No. 2016-03

ATTENTION:

OWNERS, OPERATORS AND MAINTAINERS OF PRATT & WHITNEY CANADA PW100 ENGINES

Issuing Office: Civil Aviation (National Aircraft Certification) Document No.: CASA 2016-03
File Classification No.: Z 5000-35 Issue No.: 01
RDIMS No.: 11307276 Effective Date: 2016-03-02

In-Flight Shutdowns Resulting from High Pressure Turbine Blade Distress Due to Operation in Harsh Environments

Purpose:

The purpose of this Civil Aviation Safety Alert (CASA) is to raise awareness of the possibility of Pratt & Whitney Canada (P&WC) PW100 engine in-flight shutdowns (IFSDs) resulting from high pressure turbine (HPT) blade distress due to operation in harsh environments.

Background:

There have been cases of HPT blade fractures causing in-flight shutdowns where the blade failure was a result of thermal fatigue due to blocked cooling air passages.

Experience has demonstrated that engines operating in harsh environments can require more frequent hot section refurbishment compared to engines operating in benign environments in order to avoid premature failure of HPT blades. 

Harsh environmental conditions include, but are not limited to, the presence of airborne sand and/or dust particles. In these conditions, it is most often the high pressure turbine vanes, blades and shrouds that are damaged due to the accumulation of contaminants over time in the cooling air passages. In severe cases, the cooling air passages become blocked and the blades are robbed of cooling air, which may eventually lead to HPT blade failure and subsequent IFSD. 

P&WC has published a number of recommendations in Service Information Letter S.I.L NO. PW100-172 aimed at monitoring engine hot section condition in order to avoid HPT blade fractures and their associated IFSDs. It is important to note that the tasks/intervals mentioned in the recommendations are based on operation in severe environments and should be used only as a starting point. Adjustment of the task intervals (increases or decreases) will have to be made by individual operators based on experience gained in their specific operating environment:

  1. Minimum weekly analysis of Engine Condition Trend Monitoring (ECTM) data;

  2. Borescope inspections initially at 500 flight hours (FH) and subsequently every 100 FH in order to establish a base line, or as required by ECTM trend shift, with emphasis on condition of high pressure turbine vanes and blades;

  3. Power assurance check every 100 FH if ECTM is not performed, or as required by ECTM trend shift; and

  4. Replace or clean the intercompressor bleed valve (IBV) servo screen every 100 FH on large PW100 engines operating in sandy and/or dusty environments.

Operators should ensure that the above recommendations do not conflict with the Aircraft Flight Manual (AFM) requirements. Should a conflict be identified, the AFM takes precedence in all aspects of aircraft operation.

Recommended Action:

Transport Canada recommends owners, operators and maintainers of PW100 engines familiarize themselves with the information contained in P&WC Service Information Letter S.I.L NO. PW100-172 and follow the recommendations contained therein, as appropriate, in order to avoid high pressure turbine blade fractures and IFSDs, due to operation in harsh environments.

Contact Office:

For more information concerning this issue, contact a Transport Canada Centre; or contact Hilary Ross, Continuing Airworthiness in Ottawa, by telephone at 1-888-663-3639, by fax at 613-996-9178, or by e mail at CAWWEBFeedback@tc.gc.ca.

Original signed by

Rémy Knoerr
Chief
Continuing Airworthiness

The Transport Canada Civil Aviation Safety Alert (CASA) is used to convey important safety information and contains recommended action items. The CASA strives to assist the aviation industry's efforts to provide a service with the highest possible degree of safety. The information contained herein is often critical and must be conveyed to the appropriate office in a timely manner. The CASA may be changed or amended should new information become available.

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