The FAA has issued an airworthiness concern sheet (ACS) for certain Thrush Aircraft models/serial numbers. The affected models/serial numbers can be found on the ACS, which can be viewed here. The ACS was released due to what the FAA believes is a misunderstanding in how to comply with AD 2009-26-11, which addresses fatigue cracks that can occur in the lower spar caps.
Specifically, the ACS details the FAA’s concern that the options for required repetitive inspections, which are based on the available methods for replacing the wing front lower spar cap, can be misinterpreted. If the Avenger STC SA03654AT is not used for lower spar cap replacement and if the maximum inspection interval is to be used, Thrush Custom Kit CK-AG-41 Rev A must be followed in its entirety with no deviations allowed.
The ACS requests information from owners and operators of affected Thrush aircraft. There are four questions relating to the method used to replace the front lower spar cap. The ACS provides the appropriate FAA contact to reply to with the requested information.
 for certain
Thrush Aircraft models/serial numbers. The affected models/serial
numbers can be found on the ACS. The ACS was
released due to what the FAA believes is a misunderstanding in how to
comply with AD 2009-26-11, which addresses fatigue cracks that can occur
in the lower spar caps.){kind=small}
