AD FAA-2011-0913

We are adopting a new airworthiness directive (AD) for certain Cessna Aircraft Company Model 680 airplanes. This AD was prompted by a false cross-feed command to the right-hand fuel control card, due to the cross-feed inputs on the left- and right-hand fuel control cards being connected together and causing an imbalance of fuel between the left and right wing tanks. This AD requires adding diodes to the fuel cross-feed wiring, and revising the airplane flight manual to include procedures to use when the left or right generator is selected OFF. We are issuing this AD to prevent lateral imbalance of the airplane, resulting from uncontrolled fuel cross-feed, which can be corrected by deflecting the aileron trim; deflecting the aileron trim increases the pilot's workload and could exceed the airplane's limitation in a short period of time, resulting in reduced controllability of the airplane.