Narrative:

I was flying my normally aspirated 1977 maule M-5. The weather was reported excellent VFR until a few states down when the weather in all probability would necessitate a layover somewhere along the route. I was flying on an IFR flight plan in excellent VFR conditions at 7;000 ft at -3 celsius. Ahead of me and just south and west there was developing an area of light snow that was moving slowly to the east. I investigated the weather along the route of flight in order to proceed as far south as possible before landing and overnighting. I decided to change my final destination for the day as the weather; the developing snow; to the south and west of was moving to the east and might envelop my route of flight. But the weather to the east of the route of flight to was expected to be good VFR for some time affording me an escape if the weather got worse from. As I proceeded south along the route of flight visibility went from unlimited to a mile or two and as time went by the ground at times was not visible which did not concern me because a few miles to the east of the route the weather was solid VFR. I became vigilant for the development of structural icing and detected none; but I neglected to pay attention to my carburetor heat and I lost nearly all power. ATC center was great as when I advised them of the loss of power they immediately cleared me to 5;000 ft. At 5;000 ft I had a clear view of the ground and visibility was at least 4 to 5 miles. But I could not hold 5;000 ft and center cleared me to 3;800 ft which was the lowest altitude for that sector. Fortunately power came back enough for me to maintain 4;000 ft but for some 17 miles from the onset of the loss of power I was unable to maintain a heading and strayed to the west and then back to the east. When the carburetor cleared to a comfortable level I was again on course in good VFR and I decided to go for my escape and proceed directly to the east and into solid VFR. I thanked center and canceled IFR and proceeded directly to destination for an uneventful landing and a night's layover.what did I learn from this experience? Well I certainly confirmed what I've known for years. In conditions that might support carburetor icing conditions 1) aggressively use carburetor heat in normally aspirated aircraft; 2) seek and fly in the warmest air possible as soon as possible; in my case lower; and 3) always use the aircraft checklist. I believe any one of these may have eliminated the incident. But in a broader sense my shortcoming was my emphasis on the strategic planning of the flight and my failure to equally emphasize the tactics of the flight. My escape plan worked because I planned it; but I would not have had to use it if I would have paid as much attention to the tactics of flying in winter conditions.

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Original NASA ASRS Text

Title: Maule pilot experiences carburetor icing; descends to lower altitude where problem dissipates.

Narrative: I was flying my normally aspirated 1977 Maule M-5. The weather was reported excellent VFR until a few states down when the weather in all probability would necessitate a layover somewhere along the route. I was flying on an IFR flight plan in excellent VFR conditions at 7;000 FT at -3 Celsius. Ahead of me and just south and west there was developing an area of light snow that was moving slowly to the east. I investigated the weather along the route of flight in order to proceed as far south as possible before landing and overnighting. I decided to change my final destination for the day as the weather; the developing snow; to the south and west of was moving to the east and might envelop my route of flight. But the weather to the east of the route of flight to was expected to be good VFR for some time affording me an escape if the weather got worse from. As I proceeded south along the route of flight visibility went from unlimited to a mile or two and as time went by the ground at times was not visible which did not concern me because a few miles to the east of the route the weather was solid VFR. I became vigilant for the development of structural icing and detected none; but I neglected to pay attention to my carburetor heat and I lost nearly all power. ATC Center was great as when I advised them of the loss of power they immediately cleared me to 5;000 FT. At 5;000 FT I had a clear view of the ground and visibility was at least 4 to 5 miles. But I could not hold 5;000 FT and Center cleared me to 3;800 FT which was the lowest altitude for that sector. Fortunately power came back enough for me to maintain 4;000 FT but for some 17 miles from the onset of the loss of power I was unable to maintain a heading and strayed to the west and then back to the east. When the carburetor cleared to a comfortable level I was again on course in good VFR and I decided to go for my escape and proceed directly to the east and into solid VFR. I thanked Center and canceled IFR and proceeded directly to destination for an uneventful landing and a night's layover.What did I learn from this experience? Well I certainly confirmed what I've known for years. In conditions that might support carburetor icing conditions 1) aggressively use carburetor heat in normally aspirated aircraft; 2) seek and fly in the warmest air possible as soon as possible; in my case lower; and 3) always use the aircraft checklist. I believe any one of these may have eliminated the incident. But in a broader sense my shortcoming was my emphasis on the strategic planning of the flight and my failure to equally emphasize the tactics of the flight. My escape plan worked because I planned it; but I would not have had to use it if I would have paid as much attention to the tactics of flying in winter conditions.

Data retrieved from NASA's ASRS site as of April 2012 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.