Date: 201711
Local time of day: 1201-1800
Location: ZZZ.Airport, US
Flight conditions: VMC
Weather elements / visibility: 10
Aircraft: Ultralight
Operator: Personal
Operating under: Part 91
Flight plan: None
Mission: Personal
Flight phase: Initial Approach
Airspace: Class G ZZZ
ATC / advisory: CTAF ZZZ
Reporter organization: Personal
Reporter function: Pilot Flying; Single Pilot
Reporter qualification: Flight Crew Private; Flight Crew Sea
Human factors: Situational Awareness
Anomaly: Aircraft Equipment Problem Critical
Detector: Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Provided Assistance; Aircraft Equipment Problem Dissipated; Flight Crew Diverted; Flight Crew Landed in Emergency Condition; Flight Crew Requested ATC Assistance / Clarification
Contributing factors: Aircraft; Weather
Primary problem: Weather

Narrative: Carburetor icing. Clear; cold day with visibility unlimited temps were 0 C and dew point -10 C; Alt. set. 3049. Pleasure flight began at ZZZ and meandered toward ZZZ1 at around 2300 ft MSL. Within five miles of ZZZ1; I descended to pattern altitude and I called in my position and intention to land there. A pilot was calling his pattern at ZZZ1 at the time. The ground under me was higher than at ZZZ so my AGL was less than a 1000 ft.All of a sudden my engine ran rough and quickly deteriorated into a shaking roughness even though I applied carburetor heat instantly. I lost altitude and made the decision to land off airport. I shut off the engine; shut off the fuel supply. I called the traffic landing at ZZZ1 and explained my situation and said 'mayday'. I described my plane's color and my approximate location from ZZZ1. The pilot answered and communicated back with me. Then I concentrated on landing safely on a harvested bean field close by. The landing was uneventful; the surface remarkably smooth (better than some grass field airports).I am a LSRM (Light Sport Repairman) so I troubleshot my engine. In the end it became obvious that it was a simple matter of carburetor ice on my Rotax 912 S engine. I waited about 20 minutes then restarted the engine. It started back without hesitation and ran smoothly. A thorough run-up verified that all was OK.I took off again and flew to ZZZ1: it was the closest airport. The flight was uneventful; the pattern also. After taxiing and doing one more run-up I was ready to fly back to my home airport.  A pilot flying over relayed my information to Approach who was concerned because of my 'mayday'. When in the air again; I contacted Approach and communicated with them. They asked me to call them on the phone when I landed at my home airport. I flew there directly; remaining in contact with Approach. The flight was uneventful and so was the arrival at ZZZ.Once on the ground; I called Approach on the phone and we debriefed together. They were very helpful and friendly. It seems that everybody around: the pilot I spoke with at the beginning; the FBO at ZZZ1 who picked up a radio and began driving in my general direction then the pilot above and finally the ATC were very professional; helpful and capable. All in all it was an experience without trauma and I am grateful. When it is this cold; in the future I will fly with the carburetor heat at all times.




Synopsis: Light sport aircraft pilot reported a loss of engine power led to an off-field landing; likely caused by carburetor icing.