EMER; OFF ARPT FORCED LNDG PERFORMED BY INSTRUCTOR PLT IN A C-172 AFTER EXPERIENCING FUEL STARVATION.

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AFTER A 2 HR FLT FROM LOUISVILLE; I DECIDED TO FLY LOW OVER EAGLE CREEK TO DETERMINE THE FEASIBILITY OF LNDG. THEY WERE RPTING FROM UNICOM A XWIND OF 30 MPH; SO I DOUBTED WE COULD LAND THERE. (WE HAD JUST CANCELED IFR WITH IND APCH.) AT 150 FT; I ADDED PWR FOR THE GAR; AND THE ENG BEGAN VIOLENT PWR SURGES IN EXCESS OF 500 RPM. I WAS USING RWY 21 WHICH HAS ONLY TREES AT THE DEP END; SO I CHKED ALL THE GAUGES (INCLUDING PWR INSTS) AND INSTS WHILE MAINTAINING A GRADUAL CLB. AFTER THAT; I SQUAWKED 7700 AND XMITTED A MAYDAY ON 121.5; WITH NO RESPONSE. I PLANNED ON GOING STRAIGHT INTO INTL (IND); WHICH REQUIRED NO TURNS UNTIL FINAL. HOWEVER; ABOUT 1 MIN LATER; I SAW A FIELD ( I WAS 400 FT AGL); CUT OFF THE FUEL; DUMPED THE FLAPS; AND TURNED INTO THE WIND. I LANDED WITH NO PROBS. THE ACFT AND MY STUDENT UNHARMED. I FEEL I COULD HAVE DONE A FEW THINGS BETTER: OPEN DOORS BEFORE LNDG; CONTACT IND APCH RATHER THAN 121.5. I WAS BOTHERED WITH THE FACT THAT WHEN I CALLED IND APCH ON THE GND THAT THEY SEEMED UNAWARE OF THE PROB; BUT THEY HELPED SEND THE POLICE TO FIND ME. THEIR PRIMARY RADAR WAS OTS; SO THEY WERE USING CTR RADAR (NOBODY SAW 7700 AT 400 FT AGL). HAD MY LNDG BEEN BAD; THE ONLY WAY EMER TEAMS WOULD HAVE KNOWN OF MY SIT WOULD HAVE BEEN FROM LCL OBSERVERS. THE PROB WITH THE ACFT TURNED OUT TO BE A CONGREGATION OF A FILAMENT TYPE OF SUBSTANCE BLOCKING FUEL TO THE CARB. NONE OF OUR OTHER ACFT HERE AT EAGLE CREEK HAVE THAT PROB; AND I GOT 22 GALLONS IN STANDIFORD FIELD. THE FACT THAT I DID SUMP THE TANKS BEFORE TKOF AT STANDIFORD MAKES THE MECHS THINK THERE MIGHT BE SOMETHING IN THE SYS; BUT THE SOURCE OF THE BLOCKAGE HASN'T YET BEEN DETERMINED.