FAA AD Targets Thielert Engines

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As if they didn't have enough troubles already dealing with excessive costs and a manufacturer in bankruptcy, owners of Thielert diesel engines now must cope with a proposed new Airworthiness Directive that could cost them another $1,600. The FAA posted the proposed AD on Monday, citing a problem with an oil separator that could fail, leading to an in-flight power loss or possible shutdown due to excessive gas pressure. The problem was found in servicing, and the FAA didn't note any cases of actual failure. About 250 of the Thielert engines have been installed in Diamond twins, some Piper Cherokees, and Cessna 172s in the U.S. Owners must take care of the problem within 110 flight hours of the effective date of the AD. Comments will be accepted on the proposal until May 20.

The Thielert engines proved to be expensive to maintain, and service was slow and difficult. Some of the fleet has been effectively grounded. Diamond, based in Austria, recently reintroduced its twin-engine DA42 with a choice of its own Austro diesel engines or a traditional Lycoming IO-360. Owners of the Thielert versions can trade them in for new engines, but at a cost of over $100,000.