AD FAA-2008-0854

The FAA adopts a new airworthiness directive (AD) to supersede AD 78-08-09, which applies to certain Allied Ag Cat Productions, Inc. (formerly Grumman-American) (Allied Ag Cat) Models G-164, G-164A, and G-164B airplanes. AD 78-08-09 currently requires repetitively inspecting the interior and the exterior of the main tubular spar of the rudder assembly for corrosion, taking necessary corrective action if corrosion is found, and applying corrosion protection. Since we issued AD 78-08-09, the rudder main tubular spar failed on a later production airplane. Consequently, this AD retains the actions required in AD 78-08-09 and expands the applicability to include all G-164 series airplanes. We are issuing this AD to detect and correct corrosion in the rudder main tubular spar, which could result in failure of the weld to the main spar tube. This failure could lead to loss of directional control.