What was found
(CAN) CREW DECLARED EMERGENCY DUE TO AILERON JAM - LWD CAUTION ON FLIGHT, AP LWD CAUTION MESSAGE. AFTER DISENGAGEMENT OF THE AP, ACFT NEEDED VERY STRONG FORCE TO ROLL. NEARLY IMPOSSIBLE. SUDDENLY THE AILERONS BECAME FREE AND ACFT WAS NORMAL TO CONTROL WITH NORMAL FORCE. AP SWITCHED ON AGAIN AND NO MORE FAULTS OR UNUSUAL CONTROL FEEL NOTICED. ACFT LANDED WITHOUT FURTHER DIFFICULTIES. ON GROUND MECHANICS OPENED THE AILERON PANEL’S 598BB, 599BB, 698BB AND 699BB AND FOUND THE AREA EXTREMELY CONTAMINATED WITH WATER AND DEICING FLUID. ACFT RETURNED TO SERVICE.