Summary
We propose to adopt a new airworthiness directive (AD) for certain Textron Aviation Inc. Model 680 airplanes. This proposed AD was prompted by Cessna's report of a manufacturing defect which affects the durability of the aft canted bulkhead metallic structure. The manufacturing defect directly affects the bond integrity of the vertical and horizontal stiffeners on the aft canted bulkhead metallic structure. This proposed AD would require repetitive inspections of the aft canted bulkhead, and repair if necessary. This proposed AD would also require a modification, which would terminate the repetitive inspections. We are proposing this AD to prevent disbonding of the horizontal and vertical stiffeners on the aft canted bulkhead. Loss of bond integrity could result in a structural failure that could lead to separation of the cruciform tail and loss of control of the airplane.