The FAA has proposed an airworthiness directive concerning blow-by oil separators on Thielert engines. There are 250 Thielert engines installed on airplanes of U.S. registry.
No problems have occurred, but the European Aviation Safety Agency (EASA) is concerned that the outlet of the separators is so small it could cause high pressure of the gases in the crankcase. That in turn might blow an oil seal, causing the engine to lose oil and requiring an in-flight shutdown.
The proposed solution, if the AD is issued, will be to remove certain part-number oil separators from service at an estimated cost of $1,500 per engine. Nationwide, the total expenditure could be in excess of $400,000. Because Thielert was in bankruptcy when the initial service bulletin was issued in 2008, it is not required to reimburse customers for the repair.
Those wishing to comment on the proposed AD have until May 20 to respond. Either file comments electronically and follow the instructions or mail to Docket Management Facility, U.S. Department of Transportation, 1200 New Jersey Avenue, SE., West Building Ground Floor, Room W12-140, Washington, DC 20590-0001.
