Narrative:

After a normal preflight and takeoff and about 45 minutes into the flight, the engine started to lose power. The aircraft was at 1500 MSL over a wooded area in st johns county florida. Initially, the aircraft engine lost power to 1800 RPM. I tried switching mags, confirmed fuel on, and tried alternate air/carburetor heat. About 30 seconds later, the RPM dropped to 1050-1100 which was not enough to stay airborne. I selected a landing site on a logging road. As the engine stopped, I positioned the aircraft on final and executed a power off landing. On roll-out the outboard right wingtip struck a small tree and the aircraft sustained minor damage. Postflt inspection of the fuel initially did not show any contamination. Additionally, the engine was started and run at full power for five minutes. A mechanic was consulted and could not initially find any problem. However, after running the engine about 10 more minutes at full power it started to lose power and quit. Further investigation revealed the carburetor clogged with solid contaminants. I am not sure of the source of the bad fuel. The aircraft is 49 years old and talking to other owners indicates contaminants may form in the fuel tank and be washed into the engine. Also, I have the stc for autogas and have been using it off and on during the past year. However, I have been careful to filter all fuel added to the engine finally, I have been flying the aircraft more often since the first of this year and have been getting fuel at various airports. On preflight, I checked the fuel drain and did not see any indication of bad or contaminated fuel. Also, an FAA inspector took a fuel sample at the time of the forced landing and did not find anything wrong with the fuel. It should be noted we had to run the engine almost 10 minutes after the forced landing before the engine started to lose power. The a&P mechanic could not find anything wrong in the fuel system until he opened the carburetor. Fuel samples showed good during the post-flight.

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Original NASA ASRS Text

Title: SMA ACFT MADE OFF ARPT LNDG WHEN ENGINE LOST POWER.

Narrative: AFTER A NORMAL PREFLT AND TKOF AND ABOUT 45 MINUTES INTO THE FLT, THE ENGINE STARTED TO LOSE PWR. THE ACFT WAS AT 1500 MSL OVER A WOODED AREA IN ST JOHNS COUNTY FLORIDA. INITIALLY, THE ACFT ENGINE LOST POWER TO 1800 RPM. I TRIED SWITCHING MAGS, CONFIRMED FUEL ON, AND TRIED ALTERNATE AIR/CARB HEAT. ABOUT 30 SECONDS LATER, THE RPM DROPPED TO 1050-1100 WHICH WAS NOT ENOUGH TO STAY AIRBORNE. I SELECTED A LNDG SITE ON A LOGGING ROAD. AS THE ENGINE STOPPED, I POSITIONED THE ACFT ON FINAL AND EXECUTED A PWR OFF LNDG. ON ROLL-OUT THE OUTBOARD RIGHT WINGTIP STRUCK A SMALL TREE AND THE ACFT SUSTAINED MINOR DAMAGE. POSTFLT INSPECTION OF THE FUEL INITIALLY DID NOT SHOW ANY CONTAMINATION. ADDITIONALLY, THE ENGINE WAS STARTED AND RUN AT FULL PWR FOR FIVE MINUTES. A MECHANIC WAS CONSULTED AND COULD NOT INITIALLY FIND ANY PROBLEM. HOWEVER, AFTER RUNNING THE ENGINE ABOUT 10 MORE MINUTES AT FULL PWR IT STARTED TO LOSE PWR AND QUIT. FURTHER INVESTIGATION REVEALED THE CARBURETOR CLOGGED WITH SOLID CONTAMINANTS. I AM NOT SURE OF THE SOURCE OF THE BAD FUEL. THE ACFT IS 49 YEARS OLD AND TALKING TO OTHER OWNERS INDICATES CONTAMINANTS MAY FORM IN THE FUEL TANK AND BE WASHED INTO THE ENGINE. ALSO, I HAVE THE STC FOR AUTOGAS AND HAVE BEEN USING IT OFF AND ON DURING THE PAST YEAR. HOWEVER, I HAVE BEEN CAREFUL TO FILTER ALL FUEL ADDED TO THE ENGINE FINALLY, I HAVE BEEN FLYING THE ACFT MORE OFTEN SINCE THE FIRST OF THIS YEAR AND HAVE BEEN GETTING FUEL AT VARIOUS ARPTS. ON PREFLT, I CHECKED THE FUEL DRAIN AND DID NOT SEE ANY INDICATION OF BAD OR CONTAMINATED FUEL. ALSO, AN FAA INSPECTOR TOOK A FUEL SAMPLE AT THE TIME OF THE FORCED LNDG AND DID NOT FIND ANYTHING WRONG WITH THE FUEL. IT SHOULD BE NOTED WE HAD TO RUN THE ENGINE ALMOST 10 MINUTES AFTER THE FORCED LNDG BEFORE THE ENGINE STARTED TO LOSE PWR. THE A&P MECHANIC COULD NOT FIND ANYTHING WRONG IN THE FUEL SYSTEM UNTIL HE OPENED THE CARBURETOR. FUEL SAMPLES SHOWED GOOD DURING THE POST-FLT.

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