Oil discoloration associated with carbon particles - Civil Aviation Safety Alerts (CASA) No. 2016-01


Owners, operators and maintainers of Pratt & Whitney Canada PT6A-64 AND PT6A-66D Engines

Issuing Office: Civil Aviation (National Aircraft Certification)
Document No. : CASA 2016-01
File Classification No. :

Z 5000-35

Issue No. : 01
RDIMS No. : 11204958
Effective Date: 2016-01-20


The purpose of this Civil Aviation Safety Alert (CASA) is to raise awareness of the possibility of Pratt & Whitney Canada (P&WC) PT6A-64 and PT6A-66D engine oil system carbon contamination.


There have been numerous reported events of oil discoloration associated with carbon contamination in Pratt & Whitney Canada PT6A-64 and PT6A-66D engines. Carbon contamination (indicated by a greenish hue) in the engine oil system can lead to several operational issues including oil pressure drop or fluctuation, main oil filter clogging, propeller being stiff to turn, high oil consumption and high oil temperatures. High oil temperatures and coking in the number 2 and 3 bearing areas can result in generation of carbon particles. Oil discoloration can be an indicator of contamination (although this is not always the case). As such, it is important for operators to follow the current Engine Maintenance Manual instructions to properly assess the engine condition.

Pratt & Whitney Canada has issued the following Service Information Letter (SIL) and Service Bulletins (SB) related to this issue:

  • SIL PT6A-209
  • SB 14308 Reduction gearbox scavenge line
  • SB 14346 No. 2 bearing oil nozzle with retaining ring
  • SB 14416 Power turbine air seal
  • SB 14438 Air seal assembly
  • SB 14451 No 2 bearing oil packing

Pratt & Whitney Canada is also offering a commercial support program in order to assist operators to comply with the above SB’s.

Recommended action:

Transport Canada recommends owners, operators and maintainers of these engines familiarize themselves with the information contained in Pratt & Whitney Canada SIL No. PT6A-209 (or subsequent revisions), consult the latest amendment of the appropriate maintenance manual for the list of approved oils for use in these engines, as well as follow the latest maintenance recommendations from Pratt & Whitney Canada.

Contact office:

For more information concerning this issue, contact a Transport Canada Centre; or contact Dean Ciaschini, 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
Continuing Airworthiness