What was found
(CAN) CREW REPORTS THAT UPON APPROACH AT 30FT. THE RT WING DROPPED SEVERELY. UPON POST FLIGHT ENTIRE RT WING EXCEPT THE LAST 7 FT WAS COVERED IN A .2500" TO .5" OF ICE. ALL INDICATIONS WERE GREEN APPROACH. MAINTENANCE R & R THE CONTROL SENSOR, THE ANTI-ICE CONTROLLER, AND THE ANTI-ICE SOV IAW THE AMM. THE SYSTEM HAS BEEN INDICATING PROPERLY SINCE.