9 September 2008
Carbon seal distress
There have been several occurrences of engine low oil pressure during flights that have resulted in at least four in-flight shutdowns. It has been determined that over-servicing the oil system was a factor in these events.
Shortly after departure and climbing through 19,000 feet AGL, a Cessna Citation 560XLS, powered by the PWC 545B, reported low engine oil pressure. Following shutdown of the RH engine, the crew carried out an uneventful landing. Further investigation by maintenance personnel found that there was no oil left in the RH engine (TTSN 576 hours) (TCSN 486 cycles). A visual inspection of the nacelle area found no trace of oil. The cause has been identified as oil leakage past the carbon seal on #4 turbine shaft bearing.
Pratt & Whitney Canada (P&WC) has determined that the #4 bearing seal had fractured, resulting in internal oil leakage with rapid loss of usable oil. Overfilling the oil system may impede operation of the air/oil separator, thereby increasing air pressure and causing distress inside the bearing cavities.
To improve durability/reliability in service, P&WC will soon publish a Service Bulletin introducing a redesigned carbon seal, which will improve stability and pressure balance. In the interim, Transport Canada Civil Aviation highly recommends that operators/maintenance personnel comply with the recently issued P&WC Service Information Letter (SIL) PW500-033 to address oil consumption and oil servicing issues on the PW500 series engines.
Defects, malfunctions and failures occurring on aeronautical products should be reported to Transport Canada, Continuing Airworthiness in accordance with CAR 591 mandatory Service Difficulty Reporting requirements.
For further information, contact a Transport Canada Centre, or Mr. Barry Caldwell at 613-952-4358 or e-mail firstname.lastname@example.org
For Director, National Aircraft Certification
Acting Chief, Continuing Airworthiness
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