A JETSTREAM 4100 ON APCH DECLARED AN EMER DUE TO AN UNCOMMANDED PITCH DOWN. CREW SUSPECTS EXCESSIVE DEICING WITH TYPE 4 FLUID.

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BOTH CAPT AND FO PERFORMED TACTILE CHK AS PART OF THE NORMAL EXTERIOR PREFLT. NO ICE ADHERING TO THE ACFT. BOARDED PAX. WITHIN THE 15 MINS IT TOOK TO BOARD PAX ZZZ GND PERSONNEL NOTICED ICE WAS BEGINNING TO ADHERE TO THE R WING. I TOLD THEM TO DE-ICE/ANTI-ICE DUE TO GND ICING CONDITIONS WITH TYPE 1 THEN TYPE 4 TO PRECLUDE HAVING TO TAXI BACK TO THE GATE IN THE LIKELY EVENT THE RA TURNED TO FZRA. ZZZ GND PERSONNEL COMPLIED. DURING TAXI TO THE RWY THE PRECIPITATION STOPPED. THE FO PERFORMED A PRE-TKOF CONTAMINATION CHK AND NOTICED NO ICE. WE DEPARTED ZZZ ANTI-ICE ON FLAPS 9 DEGS. WE EXPERIENCED A NORMAL ROTATION WITHOUT EXCESSIVE ELEVATOR PRESSURE. AT 500 FT AGL; WE HAD NO PROB WHEN RETRACTING THE FLAPS FROM 9 DEGS TO 0. AT 2300 FT MSL; THE ACFT ENTERED A MODERATE DSCNT. THE FO GOT ON THE CTLS AND THE ACFT RESUMED CLB. FROM THE TIME WE EXPERIENCED THE DSCNT TO THE TIME WE RESUMED CLB; WE LOST APPROX 100-200 FT. NEITHER THE AUTOPLT NOR FLT DIRECTOR WAS USED ON THE ENTIRE FLT. IN MY OPINION; THE ACFT FELT AS IF IT HAD EXCESSIVE TYPE 4 FLUID ON THE ELEVATOR. IT DID NOT FEEL LIKE A CTL MALFUNCTION. I HAND FLEW IT TO ZZZ1 WITHOUT ANY ABNORMAL PRESSURES. TO MY SHOCK; ON THE APCH TO 12R; I CALLED FOR FLAPS 9 AND THE ACFT MODERATELY PITCHED DOWN. I REQUESTED FLAPS 0 AND THE ACFT STABILIZED WITH BACK PRESSURE. AT THAT TIME; I TOLD MY FO TO DECLARE AN EMER; BUG FLAPS 0 LNDG SPEEDS AND BRIEF THE PAX. THE ACFT LANDED USING NORMAL CTL PRESSURES. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE AIRPLANE WAS DEICED WITH TYPE 1 FLUID THEN DEICED AGAIN WITH TYPE 4 FLUID AND THIS APPLICATION OF TYPE 4 WAS EXCESSIVE. THE RPTR SAID THE PITCH DOWN WAS NOT CAUSED BY SECONDARY CTLS; FLAPS OR STABILIZER. THE RPTR STATED AFTER THE EVENT AT 2300 FT THE AIRPLANE WAS HAND FLOWN AND PERFORMED NORMALLY UNTIL THE APCH WHERE AGAIN A MODERATE PITCH DOWN OCCURRED. THE RPTR SAID MAINT REMOVED THE AIRPLANE FROM SVC AND FOUND NO MALFUNCTIONS. THE RPTR STATED ON THE GND THE AIRPLANE TAIL SECTION DRIPPED FLUID FOR SOMETIME BEFORE MAINT TOWED IT AWAY.