Narrative:

I was PF at 4000 ft en route to ZZZ. We were assigned 4000 ft as ATC was ready to radar vector us to the ILS located at ZZZ. We had descended from an altitude of 16000 ft (where we were in VFR conditions) to IMC conditions. We were in IMC for approximately 15 mins. All icing equipment was on and operating. We were picking up light icing at the time. (Our PA46 is approved for flight in known icing conditions.) I was about to request a lower altitude (3000 ft) to exit icing conditions when the aircraft pitched up 20 degrees. My headset came off my head as a result of the jolt. I immediately pitched forward to compensate/avoid a stall. I was able to lower the aircraft to a 5 degree nose up pitch. I also reduced the manifold pressure when I was finally able to level the aircraft. Once I leveled; the controls were unresponsive. The yoke then pitched forward down to approximately 5 degrees. I had difficulty pitching back to level the aircraft. I then advised my PNF I had no control of the aircraft and experiencing difficulty maintaining level flight. Shortly thereafter; I regained partial control response and began a descent to a lower altitude/warmer air/VFR. Throughout; the PNF was attempting to communicate to ATC. Not having full control effectiveness; and with traffic around our position; I requested the PNF to declare an emergency and we are descending to VFR in an attempt to land at the nearest airport. ATC suggested ZZZ1 and vectored us on the VOR approach. At approximately 2500 ft MSL I regained full control authority/authorized. The flight director; however; was giving erroneous indications. I shut it off; advised the PNF to calibrate his directional gyro and initially utilized the right seat instruments until I felt the left seat instruments were operating properly which I confirmed shortly thereafter. At this time I felt comfortable that I had full control of the aircraft. Because I did not know what had occurred; I requested the ILS to ZZZ2; as ZZZ1's longest runway was under 3000 ft (below our comfort margin for this aircraft). At this time we were in/out of IFR conditions. We broke out at 2000 ft MSL. We landed uneventfully at ZZZ2. Upon inspection; we discovered no abnormalities with the control surfaces. What we believe occurred was we picked up ice on the non-protected surface of the left or right horizontal stabilizer at the gap where it meets the elevator. Ice may have wedged itself in this gap causing control ineffectiveness. As the ice melted; effectiveness of the controls was regained. No ice; however; had remained on the aircraft to corroborate this. The following day we flew the aircraft back to ZZZ (VFR) and experienced no anomalies.

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Original NASA ASRS Text

Title: PILOT AND RATED PAX ABOARD PA46 LOSE CONTROL OF THE AIRCRAFT WHILE DESCENDING IN LIGHT ICING CONDITIONS.

Narrative: I WAS PF AT 4000 FT ENRTE TO ZZZ. WE WERE ASSIGNED 4000 FT AS ATC WAS READY TO RADAR VECTOR US TO THE ILS LOCATED AT ZZZ. WE HAD DSNDED FROM AN ALT OF 16000 FT (WHERE WE WERE IN VFR CONDITIONS) TO IMC CONDITIONS. WE WERE IN IMC FOR APPROX 15 MINS. ALL ICING EQUIP WAS ON AND OPERATING. WE WERE PICKING UP LIGHT ICING AT THE TIME. (OUR PA46 IS APPROVED FOR FLT IN KNOWN ICING CONDITIONS.) I WAS ABOUT TO REQUEST A LOWER ALT (3000 FT) TO EXIT ICING CONDITIONS WHEN THE ACFT PITCHED UP 20 DEGS. MY HEADSET CAME OFF MY HEAD AS A RESULT OF THE JOLT. I IMMEDIATELY PITCHED FORWARD TO COMPENSATE/AVOID A STALL. I WAS ABLE TO LOWER THE ACFT TO A 5 DEG NOSE UP PITCH. I ALSO REDUCED THE MANIFOLD PRESSURE WHEN I WAS FINALLY ABLE TO LEVEL THE ACFT. ONCE I LEVELED; THE CTLS WERE UNRESPONSIVE. THE YOKE THEN PITCHED FORWARD DOWN TO APPROX 5 DEGS. I HAD DIFFICULTY PITCHING BACK TO LEVEL THE ACFT. I THEN ADVISED MY PNF I HAD NO CTL OF THE ACFT AND EXPERIENCING DIFFICULTY MAINTAINING LEVEL FLT. SHORTLY THEREAFTER; I REGAINED PARTIAL CTL RESPONSE AND BEGAN A DSCNT TO A LOWER ALT/WARMER AIR/VFR. THROUGHOUT; THE PNF WAS ATTEMPTING TO COMMUNICATE TO ATC. NOT HAVING FULL CTL EFFECTIVENESS; AND WITH TFC AROUND OUR POSITION; I REQUESTED THE PNF TO DECLARE AN EMER AND WE ARE DSNDING TO VFR IN AN ATTEMPT TO LAND AT THE NEAREST ARPT. ATC SUGGESTED ZZZ1 AND VECTORED US ON THE VOR APCH. AT APPROX 2500 FT MSL I REGAINED FULL CTL AUTH. THE FLT DIRECTOR; HOWEVER; WAS GIVING ERRONEOUS INDICATIONS. I SHUT IT OFF; ADVISED THE PNF TO CALIBRATE HIS DIRECTIONAL GYRO AND INITIALLY UTILIZED THE R SEAT INSTS UNTIL I FELT THE L SEAT INSTS WERE OPERATING PROPERLY WHICH I CONFIRMED SHORTLY THEREAFTER. AT THIS TIME I FELT COMFORTABLE THAT I HAD FULL CTL OF THE ACFT. BECAUSE I DID NOT KNOW WHAT HAD OCCURRED; I REQUESTED THE ILS TO ZZZ2; AS ZZZ1'S LONGEST RWY WAS UNDER 3000 FT (BELOW OUR COMFORT MARGIN FOR THIS ACFT). AT THIS TIME WE WERE IN/OUT OF IFR CONDITIONS. WE BROKE OUT AT 2000 FT MSL. WE LANDED UNEVENTFULLY AT ZZZ2. UPON INSPECTION; WE DISCOVERED NO ABNORMALITIES WITH THE CTL SURFACES. WHAT WE BELIEVE OCCURRED WAS WE PICKED UP ICE ON THE NON-PROTECTED SURFACE OF THE L OR R HORIZ STABILIZER AT THE GAP WHERE IT MEETS THE ELEVATOR. ICE MAY HAVE WEDGED ITSELF IN THIS GAP CAUSING CTL INEFFECTIVENESS. AS THE ICE MELTED; EFFECTIVENESS OF THE CTLS WAS REGAINED. NO ICE; HOWEVER; HAD REMAINED ON THE ACFT TO CORROBORATE THIS. THE FOLLOWING DAY WE FLEW THE ACFT BACK TO ZZZ (VFR) AND EXPERIENCED NO ANOMALIES.

Data retrieved from NASA's ASRS site as of May 2009 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.