Narrative:

Both captain and first officer performed tactile check as part of the normal exterior preflight. No ice adhering to the aircraft. Boarded passenger. Within the 15 mins it took to board passenger ZZZ ground personnel noticed ice was beginning to adhere to the right wing. I told them to de-ice/anti-ice due to ground 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 ground personnel complied. During taxi to the runway the precipitation stopped. The first officer performed a pre-takeoff contamination check and noticed no ice. We departed ZZZ anti-ice on flaps 9 degrees. We experienced a normal rotation without excessive elevator pressure. At 500 ft AGL, we had no problem when retracting the flaps from 9 degrees to 0. At 2300 ft MSL, the aircraft entered a moderate descent. The first officer got on the controls and the aircraft resumed climb. From the time we experienced the descent to the time we resumed climb, we lost approximately 100-200 ft. Neither the autoplt nor flight director was used on the entire flight. In my opinion, the aircraft felt as if it had excessive type 4 fluid on the elevator. It did not feel like a control malfunction. I hand flew it to ZZZ1 without any abnormal pressures. To my shock, on the approach to 12R, I called for flaps 9 and the aircraft moderately pitched down. I requested flaps 0 and the aircraft stabilized with back pressure. At that time, I told my first officer to declare an emergency, bug flaps 0 landing speeds and brief the passenger. The aircraft landed using normal control pressures. Callback conversation with reporter revealed the following information: the reporter 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 reporter said the pitch down was not caused by secondary controls, flaps or stabilizer. The reporter stated after the event at 2300 ft the airplane was hand flown and performed normally until the approach where again a moderate pitch down occurred. The reporter said maintenance removed the airplane from service and found no malfunctions. The reporter stated on the ground the airplane tail section dripped fluid for sometime before maintenance towed it away.

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Original NASA ASRS Text

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

Narrative: 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.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.