EASA SIB 2007-41
Transport Canada Advisory AV-2007-05 - Pratt & Whitney Canada PT6A engines - Electrical Discharge Damage (EDD)
Summary
Transport Canada Advisory AV-2007-05 is a service difficulty advisory concerning Pratt & Whitney Canada PT6A series engines, addressing the issue of Electrical Discharge Damage (EDD) to the No.1 bearing. This advisory applies to any aircraft equipped with these engines and highlights the risk of in-flight shutdowns and costly component replacements due to electrical arcing damage. The advisory is supported by EASA Safety Information Notice 2007-41 and provides information on the nature and causes of EDD in these engines.
What Changed
This advisory introduces awareness of the potential for electrical discharge damage in the PT6A engine accessory gear train, specifically caused by starter generator armature leakage and commutator insulation breakdown. It recommends inspection and maintenance practices to detect and prevent EDD, including periodic cleaning and resistance checks of the starter generator and visual inspection of the spline shaft. It does not mandate new regulations but serves as an important informational notice for operators and maintenance personnel.
Why It Matters
Electrical Discharge Damage can lead to severe bearing damage, reducing engine safety margins and causing unexpected in-flight shutdowns, which pose significant safety risks. For operators and maintenance organizations, understanding and monitoring EDD is critical to prevent costly repairs and ensure continued airworthiness. Compliance with recommended inspection and maintenance procedures helps maintain engine reliability and operational safety.
What To Do
Owners, operators, and maintenance facilities should familiarize themselves with Pratt & Whitney Canada's Service Information Letter No. Gen. PT6-024 on No.1 Bearing Electrical Discharge Damage. They should perform unscheduled inspections following starter generator replacement and conduct regular cleaning and resistance checks to detect armature insulation issues. Visual inspection of the starter generator spline shaft for arc damage should be done whenever the starter generator is removed. Reporting any malfunctions or failures to Transport Canada Civil Aviation is also advised.
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