Narrative:

Our airplane (xyz bae-jetstream 31) was boarded 20 mins late at ZZZ because of heavy sleet, snow and rain that was coming down. Later residual slush build up on the airplane was swept off (or was falling off on it's own). With OAT at +3 degree celsius and only light winds and rain. It was a good time to depart for H10. Start-up, taxi out for takeoff was normal. Our delay allowed for little or no standing water on the runway, takeoff on runway 35 was normal. Cleared to climb to 9000 (all anti-ice protection on), everything in the climb was normal. However, when I went to level off I immediately noticed I could not push the nose over! We were on instruments (OAT-14 degree celsius), I noticed about 1 inch strip of rime ice on leading edge of wing. My own past experience told me this is not enough ice to freeze up controls? I was able to arrest the climb somewhat with use of trim and power, while continuing to free up controls.(about 15-20 seconds) then, all of a sudden it let loose and an abrupt nose down altitude resulted. Then as soon as the frozen controls became unfrozen and nose down altitude corrected, they would begin to freeze up again! And again, with some force, it would let loose, causing another abrupt altitude change. This continued for about 2 to 4 mins. During that time we flew into clear-skies and advised sea center we were having trouble controlling pitch on our airplane, that we needed a lower altitude, immediately that was granted and as we descended into warmer conditions below-while also moving controls constantly-the pitch controls began to respond normally. (OAT at 5000 ft 1 degree celsius). In fact we did not experience even a hint of this problem from then on. Callback conversation with reporter revealed the following information: the reporter stated the airplane was not deiced with deicing fluid, but just swept with brooms by the technicians. The reporter said it appeared too warm for needing deicing fluid as most of the snow and slush was sliding off the wings and fuselage. The reporter said the top of the fuselage was not entirely clear of slush and believes this is what caused the elevator icing problem. The reporter stated maintenance inspected the elevators after the incident and concluded slush sliding off the top of the fuselage lodged in the stabilizer elevator gap.

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Original NASA ASRS Text

Title: A JET STREAM 31 ON LEVEL OFF AT 9000 FT WAS FOUND TO HAVE NO ELEVATOR CTL IN THE NOSE DOWN DIRECTION CAUSED BY ICE FORMING IN THE GAP BTWN THE AFT EDGE OF THE HORIZONTAL AND THE LEADING EDGE OF THE ELEVATOR.

Narrative: OUR AIRPLANE (XYZ BAE-JETSTREAM 31) WAS BOARDED 20 MINS LATE AT ZZZ BECAUSE OF HEAVY SLEET, SNOW AND RAIN THAT WAS COMING DOWN. LATER RESIDUAL SLUSH BUILD UP ON THE AIRPLANE WAS SWEPT OFF (OR WAS FALLING OFF ON IT'S OWN). WITH OAT AT +3 DEG CELSIUS AND ONLY LIGHT WINDS AND RAIN. IT WAS A GOOD TIME TO DEPART FOR H10. START-UP, TAXI OUT FOR TKOF WAS NORMAL. OUR DELAY ALLOWED FOR LITTLE OR NO STANDING WATER ON THE RWY, TKOF ON RWY 35 WAS NORMAL. CLRED TO CLB TO 9000 (ALL ANTI-ICE PROTECTION ON), EVERYTHING IN THE CLB WAS NORMAL. HOWEVER, WHEN I WENT TO LEVEL OFF I IMMEDIATELY NOTICED I COULD NOT PUSH THE NOSE OVER! WE WERE ON INSTRUMENTS (OAT-14 DEG CELSIUS), I NOTICED ABOUT 1 INCH STRIP OF RIME ICE ON LEADING EDGE OF WING. MY OWN PAST EXPERIENCE TOLD ME THIS IS NOT ENOUGH ICE TO FREEZE UP CTLS? I WAS ABLE TO ARREST THE CLB SOMEWHAT WITH USE OF TRIM AND POWER, WHILE CONTINUING TO FREE UP CONTROLS.(ABOUT 15-20 SECS) THEN, ALL OF A SUDDEN IT LET LOOSE AND AN ABRUPT NOSE DOWN ALTITUDE RESULTED. THEN AS SOON AS THE FROZEN CTLS BECAME UNFROZEN AND NOSE DOWN ALTITUDE CORRECTED, THEY WOULD BEGIN TO FREEZE UP AGAIN! AND AGAIN, WITH SOME FORCE, IT WOULD LET LOOSE, CAUSING ANOTHER ABRUPT ALTITUDE CHANGE. THIS CONTINUED FOR ABOUT 2 TO 4 MINS. DURING THAT TIME WE FLEW INTO CLR-SKIES AND ADVISED SEA CENTER WE WERE HAVING TROUBLE CONTROLLING PITCH ON OUR AIRPLANE, THAT WE NEEDED A LOWER ALTITUDE, IMMEDIATELY THAT WAS GRANTED AND AS WE DSNDED INTO WARMER CONDITIONS BELOW-WHILE ALSO MOVING CONTROLS CONSTANTLY-THE PITCH CONTROLS BEGAN TO RESPOND NORMALLY. (OAT AT 5000 FT 1 DEG CELSIUS). IN FACT WE DID NOT EXPERIENCE EVEN A HINT OF THIS PROB FROM THEN ON. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE AIRPLANE WAS NOT DEICED WITH DEICING FLUID, BUT JUST SWEPT WITH BROOMS BY THE TECHNICIANS. THE RPTR SAID IT APPEARED TOO WARM FOR NEEDING DEICING FLUID AS MOST OF THE SNOW AND SLUSH WAS SLIDING OFF THE WINGS AND FUSELAGE. THE RPTR SAID THE TOP OF THE FUSELAGE WAS NOT ENTIRELY CLR OF SLUSH AND BELIEVES THIS IS WHAT CAUSED THE ELEVATOR ICING PROB. THE RPTR STATED MAINT INSPECTED THE ELEVATORS AFTER THE INCIDENT AND CONCLUDED SLUSH SLIDING OFF THE TOP OF THE FUSELAGE LODGED IN THE STABILIZER ELEVATOR GAP.

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.