Narrative:

While in route at 5;500 ft; 8 miles northeast of ZZZ airport; my cessna 150 experienced a partial loss of engine power. I noticed a sudden loss of engine RPM. I responded by immediately pushing the mixture control to full rich mixture. The engine responded by increasing RPM back to my cruise power setting. After a few seconds the engine lost power again and I applied full carburetor heat. The engine RPM stabilized but full power was not being produced. I decided to turn towards the nearest airport; ZZZ municipal. As I turned towards ZZZ the engine power began to fluctuate between roughly 1;100 RPM and 2;000 RPM despite the mixture being full rich; full carb heat; and throttle open roughly half way. I had been receiving VFR radar advisories/flight following from ATC and immediately declared an emergency when the RPM began to fluctuate. I checked my fuel valve was open; mixture rich; carb heat on; magnetos on both; and primer locked. Engine gauges were normal. I briefed my passenger on an emergency landing (seat belts secure; doors ajar; evacuate when stopped) and positioned myself over ZZZ airport and ran the engine failure checklists. While in contact with ATC I squawked 7700 and advised [them] I expected a normal landing on runway at ZZZ. ATC approved a changed of frequency to the CTAF. At 4;300 ft I brought the throttle to idle and announced my intentions on the CTAF. An aircraft holding short of the runway said they would hold in position and assist me if needed after landing and would monitor my descent and watch for traffic. I established best glide speed; briefed my passenger again and continued my descent. At 1;800 ft on a downwind leg abeam the numbers I lowered 20 degrees flaps. At 1;200 ft I lowered 40 degrees flaps and turned base. I turned a short final and applied a forward slip. I told my passenger 'doors ajar!' and stated I thought we might go off the end of the runway. I touched down halfway down the runway and made a normal landing. My passenger and I smelled smoke. I turned the aircraft onto taxiway a and said 'evacuate!' I got out of the plane with the fire extinguisher. No fire or smoke was observed. I called ATC on the phone and said we were landed safe in ZZZ. The plane was towed to a maintenance shop on the airport. The mechanic thought the engine was having carburetor problems. This was my first real engine failure. I handled it identically to my engine out training flights with my CFI. My handling of the situation was 'textbook' in that I remembered every step of the emergency checklist; communicated effectively with ATC; briefed my passenger; stayed calm; and landed safely. I credit my training; my CFI; regular engine out practice; and thorough pre-flight planning and route selection. The one thing I could have done better was make 1 more revolution above the airport before turning base. This would have ensured a landing with more runway available for roll out. I could have also established best glide speed sooner to allow more time to prepare for the landing.

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Original NASA ASRS Text

Title: The pilot of a Cessna 150 experienced engine power fluctuations and loss of power. He elected to divert to the nearest airport where he made a successful emergency landing.

Narrative: While in route at 5;500 FT; 8 miles northeast of ZZZ Airport; my Cessna 150 experienced a partial loss of engine power. I noticed a sudden loss of engine RPM. I responded by immediately pushing the mixture control to full rich mixture. The engine responded by increasing RPM back to my cruise power setting. After a few seconds the engine lost power again and I applied full carburetor heat. The engine RPM stabilized but full power was not being produced. I decided to turn towards the nearest airport; ZZZ Municipal. As I turned towards ZZZ the engine power began to fluctuate between roughly 1;100 RPM and 2;000 RPM despite the mixture being full rich; full carb heat; and throttle open roughly half way. I had been receiving VFR radar advisories/flight following from ATC and immediately declared an emergency when the RPM began to fluctuate. I checked my fuel valve was open; mixture rich; carb heat on; magnetos on both; and primer locked. Engine gauges were normal. I briefed my passenger on an emergency landing (seat belts secure; doors ajar; evacuate when stopped) and positioned myself over ZZZ Airport and ran the engine failure checklists. While in contact with ATC I squawked 7700 and advised [them] I expected a normal landing on runway at ZZZ. ATC approved a changed of frequency to the CTAF. At 4;300 FT I brought the throttle to idle and announced my intentions on the CTAF. An aircraft holding short of the runway said they would hold in position and assist me if needed after landing and would monitor my descent and watch for traffic. I established best glide speed; briefed my passenger again and continued my descent. At 1;800 FT on a downwind leg abeam the numbers I lowered 20 degrees flaps. At 1;200 FT I lowered 40 degrees flaps and turned base. I turned a short final and applied a forward slip. I told my passenger 'Doors ajar!' and stated I thought we might go off the end of the runway. I touched down halfway down the runway and made a normal landing. My passenger and I smelled smoke. I turned the aircraft onto Taxiway A and said 'Evacuate!' I got out of the plane with the fire extinguisher. No fire or smoke was observed. I called ATC on the phone and said we were landed safe in ZZZ. The plane was towed to a maintenance shop on the airport. The mechanic thought the engine was having carburetor problems. This was my first real engine failure. I handled it identically to my engine out training flights with my CFI. My handling of the situation was 'textbook' in that I remembered every step of the Emergency Checklist; communicated effectively with ATC; briefed my passenger; stayed calm; and landed safely. I credit my training; my CFI; regular engine out practice; and thorough pre-flight planning and route selection. The one thing I could have done better was make 1 more revolution above the airport before turning base. This would have ensured a landing with more runway available for roll out. I could have also established best glide speed sooner to allow more time to prepare for the landing.

Data retrieved from NASA's ASRS site as of July 2013 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.