Narrative:

I was flying VFR above a solid overcast on a flight from abq to cnm. I was flight following with abq center. I was expecting breaks in the overcast near carlsbad; where I could descent to land. The ceiling was reported 2500 ft at the airport. Upon reaching cnm; the overcast was still solid. I was also flying the aircraft's FD/autoplt system. The center ATC asked me why my intentions were. I said I needed an IFR descent through the overcast. After verifying I was IFR rated; he gave me a clearance to hold northeast on cnm VOR at 8000 ft. I reached 8000 ft on the autoplt (in the clouds); but when I toggled off the descent switch; the autoplt started climbing again. I never could get it to stabilize; so I disengaged it and hand flew the hold; but I was so busy; that I couldn't thoroughly study the ILS 3 approach at cnm. (The runway 3 ILS was the approach I selected to do. After 4 or circuits; I got a clearance for the approach; but I was really behind at this time. My approach book had fallen on the floor; so I needed to find cnm ILS 3 again. Two other aircraft arrived and needed the ILS runway 3 approach. I decided at this time to abort the approach attempt; and asked for a climb to VFR and a heading to row where I could get a local radar descent through the overcast. I did this with a normal landing at row -- straight forward. Lessons learned: always be prepared. I could have studied the ILS 3 approach on the flight to carlsbad. Upon arriving; I still could have circled above the overcast and studied the ILS 3 approach before asking for the IFR clearance. Don't trust autoplts. The can screw up at the worst possible times.

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Original NASA ASRS Text

Title: BEECH A36 PLT ENCOUNTERS WX DURING VFR ON TOP CRUISE; DIVERTS TO ANOTHER ARPT.

Narrative: I WAS FLYING VFR ABOVE A SOLID OVERCAST ON A FLT FROM ABQ TO CNM. I WAS FLT FOLLOWING WITH ABQ CENTER. I WAS EXPECTING BREAKS IN THE OVERCAST NEAR CARLSBAD; WHERE I COULD DESCENT TO LAND. THE CEILING WAS REPORTED 2500 FT AT THE AIRPORT. UPON REACHING CNM; THE OVERCAST WAS STILL SOLID. I WAS ALSO FLYING THE ACFT'S FD/AUTOPLT SYS. THE CENTER ATC ASKED ME WHY MY INTENTIONS WERE. I SAID I NEEDED AN IFR DESCENT THROUGH THE OVERCAST. AFTER VERIFYING I WAS IFR RATED; HE GAVE ME A CLRNC TO HOLD NE ON CNM VOR AT 8000 FT. I REACHED 8000 FT ON THE AUTOPLT (IN THE CLOUDS); BUT WHEN I TOGGLED OFF THE DESCENT SWITCH; THE AUTOPLT STARTED CLBING AGAIN. I NEVER COULD GET IT TO STABILIZE; SO I DISENGAGED IT AND HAND FLEW THE HOLD; BUT I WAS SO BUSY; THAT I COULDN'T THOROUGHLY STUDY THE ILS 3 APCH AT CNM. (THE RWY 3 ILS WAS THE APCH I SELECTED TO DO. AFTER 4 OR CIRCUITS; I GOT A CLRNC FOR THE APCH; BUT I WAS REALLY BEHIND AT THIS TIME. MY APCH BOOK HAD FALLEN ON THE FLOOR; SO I NEEDED TO FIND CNM ILS 3 AGAIN. TWO OTHER ACFT ARRIVED AND NEEDED THE ILS RWY 3 APCH. I DECIDED AT THIS TIME TO ABORT THE APCH ATTEMPT; AND ASKED FOR A CLB TO VFR AND A HEADING TO ROW WHERE I COULD GET A LOCAL RADAR DESCENT THROUGH THE OVERCAST. I DID THIS WITH A NORMAL LANDING AT ROW -- STRAIGHT FORWARD. LESSONS LEARNED: ALWAYS BE PREPARED. I COULD HAVE STUDIED THE ILS 3 APCH ON THE FLIGHT TO CARLSBAD. UPON ARRIVING; I STILL COULD HAVE CIRCLED ABOVE THE OVERCAST AND STUDIED THE ILS 3 APCH BEFORE ASKING FOR THE IFR CLRNC. DON'T TRUST AUTOPLTS. THE CAN SCREW UP AT THE WORST POSSIBLE TIMES.

Data retrieved from NASA's ASRS site as of January 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.