12 April 2005
Possible oil contamination
PT6A-67D operators have reported incidents where the engine oil was found contaminated. The engines exhibited black oil/carbon build-up in the No. 2 and No. 3-4 bearing oil tubes, as well as in the oil filter. In some cases, this resulted in oil pressure fluctuations and/or accessories gearbox scavenge pump inlet or main oil filter blockage.
Detailed investigations have identified the source of the oil contamination to be the degradation of the nitrile butadiene rubber (NBR) oil cooler lines, which are supplied by the aircraft manufacturer. These lines are being replaced on attrition with improved teflon lines. The FAA has been notified and they are currently reviewing the situation to determine if any mandatory action is required.
|Part||Old Part Numbers||New (Teflon) Oil Cooler Lines|
Pratt & Whitney Canada (P&WC) Service Information Letter (SIL) No. PT6A-112 was issued to explain this oil discoloration and highlight the PT6A-67D Maintenance Manual, Section 72-60-00, procedures to be followed.
Transport Canada recommends operators confirm the presence of carbon in oil by performing:
- An oil filter patch test, and visual review of oil sample for carbon in suspension in oil as presented in P&WC SIL No. PT6A-112;
- An inspection of the accessory gearbox scavenge pump inlet screen for contamination as per Section 72-60-00 of the PT6A-67D Maintenance Manual; and ;
- Report any further defects or occurrences via the Service Difficulty Reporting program.
Transport Canada also recommends that operators replace the existing aircraft oil cooler lines made of nitrile butadiene rubber, P/Ns 33099F-12-0290 and 33099F-12-0414, with the new ones made of Teflon, P/Ns 124J002-12CR-0290 and 124J002-12CR-0414.
For further information contact a Transport Canada Centre, or call Mr. Luc Deniger, Senior Engineer, Continuing Airworthiness, Ottawa, telephone 613 952-5385, facsimile 613 996-9178 or e-mail firstname.lastname@example.org
For the Director, Aircraft Certification
Chief, Continuing Airworthiness
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