Incident Overview
During a climb to and level-off at 37,000 feet, the flight crew of a McDonnell Douglas DC-10-30F freighter observed that the control yokes for the captain and first officer moved laterally independently of each other, with a displacement of approximately two inches. The crew subsequently performed an unscheduled landing at Washington Dulles International Airport, which was uneventful.
Post-Flight Inspection
After landing, maintenance personnel inspected the flight control system. The left aileron cable tension regulator assembly was found to have a decrease in cable tension. Upon lubrication, the unit jumped to a position that restored proper cable tension between the control wheel and the aileron control loop.
Operator Action
In response to this finding, the operator revised its lubrication program for the cable tension regulator assemblies. The previous practice was "on condition" lubrication; this was changed to a fixed interval of every 2,500 hours of operation, which equates to more than once per year.