JAMMED FLT CTLS FROM ICE ACCUMULATION.

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JUST PRIOR TO PUSHBACK IN AN MD-88 AT YUL; A LIGHT RAIN STARTED. DUE TO THE OUTSIDE AIR TEMP OF 25 DEGS F; WE WENT TO BE DEICED. THE GND CREW WAS WAITING AND DEICED THE ACFT IN ACCORDANCE WITH COMPANY PROCS WITH TYPE I FLUID/50-50 MIX. THE ACFT WAS SAID TO BE 'FREE OF ICE' AND WE TAXIED TO RWY 6L FOR TKOF. AS WE LEFT THE DEICE AREA THE RAIN INCREASED IN INTENSITY. WE DELAYED EXTENDING OUR FLAPS/SLATS UNTIL APCHING THE END OF THE RWY. AS WE CONFIGURED WE NOTICED CLR ICE ACCUMULATING ON THE WIPER ARMS. WHEN WE INITIATED THE FLT CTL CHK WE FOUND WE COULD NOT MOVE THE YOKE AFT OF NEUTRAL AND THAT FORWARD MOVEMENT WAS RESTR. WE RETURNED TO DEICE AND WERE TREATED AGAIN WITH TYPE I/50-50 AND TYPE II ULTRA. AFTER ABOUT 1 HR IN CONSTANT RAIN; DUE TO THE SUBSEQUENT BUILDUP OF ICE; WE WERE NEVER ABLE TO FREE THE FLT CTLS; EVEN AFTER FURTHER ATTEMPTS AT DEICE. WE RETURNED TO THE GATE AND CANCELED. OBSERVATIONS: WE WERE IMPRESSED WITH HOW RAPIDLY THE ICE BUILT UP EVEN ON SURFACES THAT HAD BEEN DEICED WITH TYPE I. IT WAS DISCONCERTING TO BE MADE AWARE OF HOW SUSCEPTIBLE THE MD-88 ELEVATOR CTLS ARE TO ICING; ESPECIALLY ON THE GND. WE WERE FORTUNATE TO HAVE DELAYED THE FLT CTL CHK UNTIL JUST BEFORE TKOF.