Summary
We propose to supersede Airworthiness Directive (AD) 78-08-09, which applies to certain Allied Ag Cat Productions, Inc. (formerly Grumman-American) 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 proposed AD would retain the actions required in AD 78-08-09 and expand the applicability to include all G-164 series airplanes. We are proposing 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.