PVT PLT OF A SMA SEL WAS FORCED TO MAKE AN OFF ARPT FORCED LNDG DUE TO ENG FAILURE.

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MY WIFE AND I DEPARTED WATERBURY-OXFORD ARPT IN CENTRAL CT IN THE MORNING AFTER TOPPING OF THE TANKS WITH 5 GALLONS OF 100LL FUEL AND COMPLETING A FULL PREFLT INSPECTION ON ACFT. A PIPER WARRIOR PA28-151; RENTED TO ME BY (FBO X). I WAS PIC. THE FLT TO NEW CASTLE COUNTY ARPT IN DE WAS UNEVENTFUL AND WE LANDED AND TAXIED TO (FBO Y); WHERE I WATCHED AN EMPLOYEE FILL THE AIRPLANE WITH 15.3 GALLONS OF 100LL FUEL. EACH TANK TOOK APPROX 7.65 GALLONS. I THEN SECURED THE ACFT WITH CHOCKS AND LEFT THE ARPT. I RETURNED TO THE ACFT WITH MY BROTHER-IN- LAW. I PERFORMED ANOTHER FULL PREFLT INSPECTION AND FOUND NOTHING UNUSUAL. BOTH FULL FUEL TANKS WERE SUMPED AND I OBSERVED A BLUE COLOR AND NO VISIBLE CONTAMINANTS IN THE FUEL. THE ACFT HAD APPROX 6.5 QUARTS OF OIL AND THE FORWARD FUEL DRAIN WAS SUMPED. PRIOR TO DEP; A MAGNETO CHK AND CARB HEAT CHK RESULTED IN RPM DROPS WITHIN THE ACCEPTABLE RANGE AND NO NOTICEABLE ENG PROBS. I DEPARTED NEW CASTLE COUNTY ARPT. AFTER 1.2 HRS OF FLYING WE WERE COMPLETING A LOW ORBIT WHEN I ATTEMPTED TO CLB FROM 700 FT AGL. DESPITE FULL THROTTLE AND FULL-RICH MIXTURE THE RPM'S NEVER INCREASED ABOVE 2000 FT. I ACTIVATED CARB HEAT; SWITCHED TANKS; CHKED MAGNETOS; FUEL PUMP SWITCH AND ENG PRIMER. THIS FAILED TO INCREASE ENG RPM. I DETERMINED THE HDG TO THE NEAREST ARPT (SUMMIT) USING A GPS RECEIVER AND PROCEEDED ON COURSE. AFTER A COUPLE OF MINS; THERE WAS A LOUD NOISE FROM IN FRONT OF THE FIREWALL AND THE ENG DROPPED TO 1400 RPM. AT THIS POINT I WAS UNABLE TO MAINTAIN ALT. I IDENTED A LNDG SIGHT; CALLED MAYDAY ON 121.5 AND 122.7 MHZ; PREPARED THE CABIN FOR AN OFF-FIELD LNDG BY INSTRUCTING MY PAX TO CHK HIS SEATBELT AND CRACK OPEN THE CABIN DOOR; AND BEGAN MY APCH. CONCURRENT WITH MY APPLICATION OF THE 1ST FLAP SETTING THERE WAS ANOTHER LOUD ENG NOISE AND THE ENG RACED TO 3000 RPM. THE PLANE BEGAN TO SHAKE VIOLENTLY AND I IMMEDIATELY PULLED THE MIXTURE; PULLED THE THROTTLE; SHUT-OFF THE ELECTRICAL AND MAGNETO SYS AND TURNED THE FUEL SELECTOR TO THE OFF POS. I THEN LANDED THE AIRPLANE IN A SOYBEAN FIELD WITHOUT INJURIES OR DAMAGE TO THE ACFT. I CONTACTED THE FAA; I THEN CALLED THE LCL POLICE. UPON RETURNING TO THE PLANE THAT EVENING; I HAND TURNED THE PROP AND COULD NOT COMPLETE A REVOLUTION. AT AN APPROX POS OF 3 O'CLOCK; THE PROP WOULD BIND AND WOULD NOT TURN. I ENLISTED THE HELP OF A LCL FARMER AND WE PROCEEDED TO TOW THE AIRPLANE TO A HELPFUL CITIZEN'S BACKYARD. ON SUNDAY; I RETURNED TO THE AIRPLANE WHERE I MET WITH THE OWNER OF THE FBO WHERE I RENTED THE PLANE AND AN FAA INSPECTOR; FROM AEA-FSDO-17. WE TOOK FUEL SAMPLES FROM EACH WING WHICH HAVE BEEN SENT FOR ANALYSIS AND REMOVED THE SPARK-PLUGS FROM THE 2 FORWARD CYLINDERS. AS THE PROP WAS ROTATED IT WAS OBSERVED THAT THE CYLINDERS DID NOT MOVE. FAA INDICATED THAT PRELIMINARY INVESTIGATION SUGGESTED THAT THE FORCED LNDG HAD BEEN CAUSED BY 'COMPLETE AND CATASTROPHIC ENG FAILURE;; AND THAT THE PIC WAS NOT CULPABLE FOR THE FAILURE. IT IS IMPORTANT TO STRESS THAT THE FAA HAS CLASSIFIED THIS EVENT AS AN INCIDENT SINCE THERE WERE NO INJURIES OR DAMAGE TO THE ACFT. IT IS VERY DIFFICULT TO ASSESS THE CAUSES OF THE ENG FAILURE PRIOR TO THE RETURN OF THE FUEL SAMPLES AND THE TEAR-DOWN OF THE ENG. IT IS SUSPECTED THAT A CONNECTING ROD FROM A PISTON FAILED; RESULTING IN ADDITIONAL DAMAGE TO THE CRANKCASE COMPONENTS WHICH EVENTUALLY RENDERED THE ENG INOP. AS INDICATED; PREFLT EXAMINATION DETECTED NO NOTICEABLE MECHANICAL PROBS OR LAPSES IN SCHEDULED MAINT. ASIDE FROM COMPONENT FATIGUE AND SUBSEQUENT FAILURE OF THE CONNECTING ROD; ANOTHER SUSPECTED CAUSE IS FUEL CONTAMINATION. AN IMPROPER OCTANE OR FUEL MIXTURE COULD RESULT IN DETONATION WHICH IS A KNOWN CAUSE OF ENG FAILURE. FUEL FROM FBO AND THE AIRPLANE HAVE BEEN COLLECTED AND SUBMITTED FOR ANALYSIS.