What happened
On March 26, 2014, a Cessna 560XL, registration N580QS, was landing at Cherry Capital Airport (TVC) in Traverse City, Michigan, when the flight crew experienced a loss of rudder authority. The flying pilot noted that the rudder pedals felt hard or frozen during the final approach. Despite the resistance, the pilot completed an uneventful landing, and the aircraft remained undamaged.
Following the landing, the non-flying pilot confirmed the stiffness of the pedals. Once the aircraft slowed to a safe speed, the crew was able to free the pedals sufficiently to taxi to the ramp. However, after the engines were shut down, the rudder pedals remained stiff and required more input than normal to operate. There were no injuries to the two pilots or two passengers on board.
The investigation
Investigators examined the aircraft and found evidence of moisture and pooled liquid consistent with deicing fluid in the tailcone compartment. A witness mark consistent with a water line was also observed in the fuselage.
Upon inspecting the galley drain area, investigators found water exiting from the black foam insulation surrounding the drain tube's heating element. The foam showed deformation consistent with the expansion of frozen water. Further inspection revealed an opening in the drain tube itself. Testing confirmed that the galley drain heating element was inoperative.
Laboratory testing conducted by Cessna simulated various scenarios of water introduction to the control cables. The tests demonstrated that ice could bridge the gap between the rudder cables and the drain tube insulation, resulting in an increase in the force required to move the rudder pedals.