Narrative:

Engine quit while executing the RNAV approach at the ZZZ airport. A forced landing was made into a farmer's field without any injury or damage to the aircraft or property. The event occurred at the leveloff at the minimum descent altitude on the approach. The reason the engine quit was due to fuel line icing which cut off the fuel flow from the right tank. After 3.5 hours of flight time the left tank went dry even though the tank gauge was at 1/4 tank which is a whole other issue to be addressed. The right tank showed 1/3 of a tank and the fuel selector was turned to right tank position during the forced landing without any sign of the engine restarting. The event occurred rather fast since the aircraft was only 500 ft AGL at the time of the occurrence. Investigating the situation on the ground; the right tank had 10 usable gallons and the left tank was dry. When I checked the drain sump on the right tank; I noticed ice crystals in the sump cup; therefore; concluded the right tank must have froze up at the tank screen inside the tank. The reason the tank had water in it was due to a tank repair that was done the day before the flight. The tank had been welded on prior to this flight to fix a small crack in the tank. The welding process requires filling the tank with water in order to keep any fumes in the tank from igniting. The maintenance staff thought they rid the tank of any water by sloshing fuel through it several times. After maintenance; the plane was brought back to its cold storage hangar. Aware of a possible water issue; the plane was brought back to be heated at the maintenance hangar 45 mins prior to the flight. The right tank had been checked twice for water contamination with no visual sign of contamination. The temperature the night before was in the teens and it could therefore be concluded that there must have been frozen ice particles in the fuel and the 45 mins prior to the flight was not long enough for the water to come out of suspension in the fuel. To conclude; it was unfortunate that we were not able to remove the water vapor from the fuel prior to the flight. It was also unfortunate that we were 3 mi shy of the airport where we planned to stop and refuel at.

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Original NASA ASRS Text

Title: C172 ENGINE QUIT ON APPROACH. PLT EXECUTED AN EMERGENCY LANDING WITHOUT HARM TO PERSONS OR THE AIRCRAFT.

Narrative: ENG QUIT WHILE EXECUTING THE RNAV APCH AT THE ZZZ ARPT. A FORCED LNDG WAS MADE INTO A FARMER'S FIELD WITHOUT ANY INJURY OR DAMAGE TO THE ACFT OR PROPERTY. THE EVENT OCCURRED AT THE LEVELOFF AT THE MINIMUM DSCNT ALT ON THE APCH. THE REASON THE ENG QUIT WAS DUE TO FUEL LINE ICING WHICH CUT OFF THE FUEL FLOW FROM THE R TANK. AFTER 3.5 HRS OF FLT TIME THE L TANK WENT DRY EVEN THOUGH THE TANK GAUGE WAS AT 1/4 TANK WHICH IS A WHOLE OTHER ISSUE TO BE ADDRESSED. THE R TANK SHOWED 1/3 OF A TANK AND THE FUEL SELECTOR WAS TURNED TO R TANK POS DURING THE FORCED LNDG WITHOUT ANY SIGN OF THE ENG RESTARTING. THE EVENT OCCURRED RATHER FAST SINCE THE ACFT WAS ONLY 500 FT AGL AT THE TIME OF THE OCCURRENCE. INVESTIGATING THE SITUATION ON THE GND; THE R TANK HAD 10 USABLE GALLONS AND THE L TANK WAS DRY. WHEN I CHKED THE DRAIN SUMP ON THE R TANK; I NOTICED ICE CRYSTALS IN THE SUMP CUP; THEREFORE; CONCLUDED THE R TANK MUST HAVE FROZE UP AT THE TANK SCREEN INSIDE THE TANK. THE REASON THE TANK HAD WATER IN IT WAS DUE TO A TANK REPAIR THAT WAS DONE THE DAY BEFORE THE FLT. THE TANK HAD BEEN WELDED ON PRIOR TO THIS FLT TO FIX A SMALL CRACK IN THE TANK. THE WELDING PROCESS REQUIRES FILLING THE TANK WITH WATER IN ORDER TO KEEP ANY FUMES IN THE TANK FROM IGNITING. THE MAINT STAFF THOUGHT THEY RID THE TANK OF ANY WATER BY SLOSHING FUEL THROUGH IT SEVERAL TIMES. AFTER MAINT; THE PLANE WAS BROUGHT BACK TO ITS COLD STORAGE HANGAR. AWARE OF A POSSIBLE WATER ISSUE; THE PLANE WAS BROUGHT BACK TO BE HEATED AT THE MAINT HANGAR 45 MINS PRIOR TO THE FLT. THE R TANK HAD BEEN CHKED TWICE FOR WATER CONTAMINATION WITH NO VISUAL SIGN OF CONTAMINATION. THE TEMP THE NIGHT BEFORE WAS IN THE TEENS AND IT COULD THEREFORE BE CONCLUDED THAT THERE MUST HAVE BEEN FROZEN ICE PARTICLES IN THE FUEL AND THE 45 MINS PRIOR TO THE FLT WAS NOT LONG ENOUGH FOR THE WATER TO COME OUT OF SUSPENSION IN THE FUEL. TO CONCLUDE; IT WAS UNFORTUNATE THAT WE WERE NOT ABLE TO REMOVE THE WATER VAPOR FROM THE FUEL PRIOR TO THE FLT. IT WAS ALSO UNFORTUNATE THAT WE WERE 3 MI SHY OF THE ARPT WHERE WE PLANNED TO STOP AND REFUEL AT.

Data retrieved from NASA's ASRS site as of May 2009 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.