AD calls for Thielert clutch assembly inspection

August 31, 2010

The FAA has issued an airworthiness directive for airplanes equipped with certain Thielert engines to prevent engine in-flight shutdown leading to loss of control of the airplane.

The AD is based on a similar European directive, which was issued after in-flight shutdown incidents were reported on airplanes with TAE 125 engines. It calls for identifying the serial numbers of clutch assemblies installed on the airplane and replacing them if the serial number matches one of those listed in the Thielert service bulletin. The AD becomes effective Sept. 9.

Preliminary investigations showed that the in-flight incidents were “mainly the result of nonconforming disc springs (improper heat treatment) used in a certain production batch of the clutch,” according to the AD.

The FAA calls for the immediate adoption of the AD because an unsafe condition exists, the AD notes. “The FAA has found that the risk to the flying public justifies waiving notice and comment prior to adoption of this rule because of the need for operators to comply with some of the AD actions before further flight. Therefore, it was determined that notice and opportunity for public comment before issuing this AD are impracticable and that good cause exists for making this amendment effective in fewer than 30 days.” The agency invites the public to send written relevant data, views, or arguments about the AD. See the AD for details.