Proposed Citation AD based on lab results

A proposed AD that would require replacing the horizontal stabilizer trim actuator (HSTA) every 18 months on Citation 650s is based on a discovery in lab tests that the no-back friction brake within the HSTA “can degrade and allow the actuator to move without a command if an electrical failure is also present,” according to Cessna. At press time, the manufacturer said it had not received any reports of this condition in the field. Cessna is supplying data to the FAA to determine if an alternative to the replacement interval is “both safe and practical."