Airworthiness Advisory Circulars - Part 6-29 - General advice
Part 6 - General advice
AAC 6-29 Amdt 1
PWC PT6A Series Engines HSI Policy
A number of Australian Pratt and Whitney Canada PT6A operators have elected to delete a fixed time HSI interval for the PT6A in favour of basing the HSI on the results of engine condition trend monitoring.
Basing a HSI on trend monitoring is a documented PWC TBO procedure for certain PT6A models, and is acceptable to this Authority. However, operators of PT6A engines should be aware that in-service experience with the PT6A engine has indicated a PT6A series engine will require at least one HSI in a service life. PT6A operators should be aware trend monitoring permits the HSI to be planned at the operator's convenience rather than at at a fixed time. Trend monitoring should not be considered as an alternative to a HSI.
Failure to carry out a HSI will not only result in degradation of the engine hot section components to a level where repair becomes extremely expensive, but of concern to CASA is that performance may deteriorate to a level where certificated power is no longer available, or engine failure may occur at a critical stage of flight.
Accordingly, PT6A operators who elect to establish HSI intervals based on engine condition trend monitoring require a System of Maintenance approved which details;
|1. The trend monitoring program shall commence with the engine in a new or newly overhauled condition or alternatively, following a HSI and a compressor wash.|
Note: To establish credibility of any HSI, an engine performance run should be carried out before and after the HSI.
|2. Compliance with the principles and procedures detailed in Pratt and Whitney Canada ECTM Analytical Guide (EAG) manual.|
|3. Documentation necessary for the recording of required data.|
|4. Current or acceptable revision status of applicable PWC Engine Condition Monitoring Program, and applicable Instruction Manual.|
|5. Necessary equipment (computer, printer, calculator etc) to run the PWC ECTM program.|
|6. ECTM training procedures for all persons involved in the recording, entry and appraisal of ECTM.|
|7. A Procedures Manual (and Operating Manual if applicable) detailing practices and procedures required to be observed by all persons involved in the recording, entry and appraisal of ECTM.|
|8. In-flight parameters are recorded on each flying day, or every 5 flight hours.|
|9. At least twice weekly, those parameters are plotted and assessed by an appropriate person.|
|10. Appropriate procedures to respond to deviations from delta as detailed in the PWC EAG manual.|
|11. A system of recording and retention of all data and responses to ECTM.|