51-18-01 CESSNA: Applies to All Model T-50 Aircraft.
Compliance required at each periodic inspection.
Two reports of loss of rudder control in flight as a result of fatigue failure of rudder torque tube have been received. Failures occur in the lower rib and pylon area. For complete inspection of the affected area, a section of the fabric should be opened by cutting along the leading edge upward to permit removal of a 10-inch section of the leading edge wood block then aft along the lower rib flange. This method will facilitate closing. (Replacement of removed wood leading edge section with lacing cord similar to original fastening is satisfactory.) Since the rudder torque tube is not heat-treated, cracks up to approximately 3/4 inch in length may be stop-drilled and welded. Where cracks have progressed further, it is recommended that the lower section of the torque tube be replaced by splicing between the No. 1 and No.2 ribs in accordance with Manual 18 practice.This supersedes AD 47-05-02.