Narrative:

While flying cross country from crq to dvt over borrego springs, ca, my RPM's began to fluctuate and the engine cut in and out in a progressive manner. Just prior to this I had initiated a climb from 7500 ft MSL to 9500 ft MSL and had just leveled off. At this time I was getting flight following from ATC and had advised them of the problem and advised that I would be descending back to 7500 ft MSL and turning around to return to crq. I did not realize at this time that I had carburetor icing. I thought there might be a problem with the carburetor or engine caused by the increase in altitude and hoped by descending back to 7500 ft the situation would correct itself. At 7500 ft MSL the problem persisted and at that time I decided to land at L08. As I went through my descent checklist, I realized that the problem was probably carburetor icing and applied carburetor heat. As I continued to descend the problem went away. After landing, I conducted a runup and checked the magnetos and everything checked out fine. This being the first experience I had with carburetor icing, I called my flight school and spoke with an instructor and we agreed this was a case of carburetor icing. I then conducted another preflight and runup and everything checked out. I continued on with my flight without incident. Being in VMC and over the desert, the last thing I thought of was carburetor icing. Also, when the situation began, I was indecisive about landing right away or returning to crq. I realize now the best thing, if possible, is to land as soon as practical and check everything out on the ground.

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Original NASA ASRS Text

Title: C152 PLT LOST ENG PWR AND HAD A ROUGH RUNNING ENG DUE TO UNRECOGNIZED CARB ICING.

Narrative: WHILE FLYING XCOUNTRY FROM CRQ TO DVT OVER BORREGO SPRINGS, CA, MY RPM'S BEGAN TO FLUCTUATE AND THE ENG CUT IN AND OUT IN A PROGRESSIVE MANNER. JUST PRIOR TO THIS I HAD INITIATED A CLB FROM 7500 FT MSL TO 9500 FT MSL AND HAD JUST LEVELED OFF. AT THIS TIME I WAS GETTING FLT FOLLOWING FROM ATC AND HAD ADVISED THEM OF THE PROB AND ADVISED THAT I WOULD BE DSNDING BACK TO 7500 FT MSL AND TURNING AROUND TO RETURN TO CRQ. I DID NOT REALIZE AT THIS TIME THAT I HAD CARB ICING. I THOUGHT THERE MIGHT BE A PROB WITH THE CARB OR ENG CAUSED BY THE INCREASE IN ALT AND HOPED BY DSNDING BACK TO 7500 FT THE SIT WOULD CORRECT ITSELF. AT 7500 FT MSL THE PROB PERSISTED AND AT THAT TIME I DECIDED TO LAND AT L08. AS I WENT THROUGH MY DSCNT CHKLIST, I REALIZED THAT THE PROB WAS PROBABLY CARB ICING AND APPLIED CARB HEAT. AS I CONTINUED TO DSND THE PROB WENT AWAY. AFTER LNDG, I CONDUCTED A RUNUP AND CHKED THE MAGNETOS AND EVERYTHING CHKED OUT FINE. THIS BEING THE FIRST EXPERIENCE I HAD WITH CARB ICING, I CALLED MY FLT SCHOOL AND SPOKE WITH AN INSTRUCTOR AND WE AGREED THIS WAS A CASE OF CARB ICING. I THEN CONDUCTED ANOTHER PREFLT AND RUNUP AND EVERYTHING CHKED OUT. I CONTINUED ON WITH MY FLT WITHOUT INCIDENT. BEING IN VMC AND OVER THE DESERT, THE LAST THING I THOUGHT OF WAS CARB ICING. ALSO, WHEN THE SIT BEGAN, I WAS INDECISIVE ABOUT LNDG RIGHT AWAY OR RETURNING TO CRQ. I REALIZE NOW THE BEST THING, IF POSSIBLE, IS TO LAND AS SOON AS PRACTICAL AND CHK EVERYTHING OUT ON THE GND.

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.