What was found
UPON INVESTIGATION OF SKIN CRACK AT FS 166.4 IN THE TOP AREA OF EMPENNAGE, DETERMINED CESSNA FACTORY INSTALLED AUTOPILOT PITCH SERVO ATTACHED TO STA 166.4 BULKHEAD AND AREA SKIN FAILED. A TEAR-LIKE CRACK OCCURRED ON SKIN AND TWO CRACKS FOUND ON LOCATION BULKHEAD IN AREA OF SERVO MOUNT ATTACH. INVESTIGATION DISCLOSED SERVO MOUNT DID NOT INCLUDE ANY DOUBLER OR STIFFENER TO SKIN OR BULKHEAD. CESSNA AUTOPILOT SM ALSO DID NOT INCLUDE DOUBLER OR STIFFENER TO SUPPORT SERVO MOUNT.