Narrative:

I normally fly IFR, using the autoplt during en route operations. I was not using the autoplt this trip because it appeared to be out of adjustment on altitude hold, later confirmed. We were flying en route at 5000 ft in IMC, in light rain, temperature hovering right at 0 degrees C. My wife was not feeling well and I was concerned about proceeding another hour to our destination with the WX as it was, and daylight starting to diminish. As I was talking with my wife, I noticed that we had entered a turning dive, creating the altitude deviation. Recovery commenced upon realizing the situation. We ended up landing about 1 hour short of the original destination. I believe that distrs contributed to this. The other item I should cite is how quickly the deviation took place. Reflecting back on it, that was the major surprise. I can't recall another incident in my 35 yrs of flying where altitude was lost so quickly. Afterward it occurred to me that perhaps I was experiencing freezing in the static system which could have affected the readouts. However, I have no evidence of that and I haven't researched the reasonableness of that.

Google
 

Original NASA ASRS Text

Title: PA32 PLT, FLYING IN INST CONDITIONS IN ZNY AIRSPACE, EXPERIENCES MOMENTARY LOSS OF CTL AFTER BECOMING DISTR.

Narrative: I NORMALLY FLY IFR, USING THE AUTOPLT DURING ENRTE OPS. I WAS NOT USING THE AUTOPLT THIS TRIP BECAUSE IT APPEARED TO BE OUT OF ADJUSTMENT ON ALT HOLD, LATER CONFIRMED. WE WERE FLYING ENRTE AT 5000 FT IN IMC, IN LIGHT RAIN, TEMP HOVERING RIGHT AT 0 DEGS C. MY WIFE WAS NOT FEELING WELL AND I WAS CONCERNED ABOUT PROCEEDING ANOTHER HR TO OUR DEST WITH THE WX AS IT WAS, AND DAYLIGHT STARTING TO DIMINISH. AS I WAS TALKING WITH MY WIFE, I NOTICED THAT WE HAD ENTERED A TURNING DIVE, CREATING THE ALTDEV. RECOVERY COMMENCED UPON REALIZING THE SIT. WE ENDED UP LNDG ABOUT 1 HR SHORT OF THE ORIGINAL DEST. I BELIEVE THAT DISTRS CONTRIBUTED TO THIS. THE OTHER ITEM I SHOULD CITE IS HOW QUICKLY THE DEV TOOK PLACE. REFLECTING BACK ON IT, THAT WAS THE MAJOR SURPRISE. I CAN'T RECALL ANOTHER INCIDENT IN MY 35 YRS OF FLYING WHERE ALT WAS LOST SO QUICKLY. AFTERWARD IT OCCURRED TO ME THAT PERHAPS I WAS EXPERIENCING FREEZING IN THE STATIC SYS WHICH COULD HAVE AFFECTED THE READOUTS. HOWEVER, I HAVE NO EVIDENCE OF THAT AND I HAVEN'T RESEARCHED THE REASONABLENESS OF THAT.

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.