Narrative:

During a training flight, I was with a student pilot practicing maneuvers. During a 'turns around a point' maneuver the engine faltered, losing approximately 600-700 RPM. As we were low level (1200 ft AGL), I immediately decided to make an emergency landing. As we rolled out of the turn, the landing area I spotted was a large sandbank along the river. I made one mayday call on the unicom frequency that I was monitoring with no reply. I then transmitted a mayday call on 121.5 prior to making the forced landing, while expediting normal emergency procedures. I used what little power I had to make it to my landing destination and as it was to be sand, a soft field landing was appropriate. The engine had 2 power surges prior to landing. A safe forced landing was accomplished with slight damage to the propeller. Moisture in the air might have provided carburetor icing, however because of the large power loss, I believe that the cause was fuel related. However, post incident inspection revealed no fuel contamination or problems. It seems rather a mystery.

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Original NASA ASRS Text

Title: EMER FORCED OFF ARPT LNDG WHEN ACFT EQUIP PROBLEM CAUSES ENG SURGES AND LOSS OF PWR.

Narrative: DURING A TRAINING FLT, I WAS WITH A STUDENT PLT PRACTICING MANEUVERS. DURING A 'TURNS AROUND A POINT' MANEUVER THE ENG FALTERED, LOSING APPROX 600-700 RPM. AS WE WERE LOW LEVEL (1200 FT AGL), I IMMEDIATELY DECIDED TO MAKE AN EMER LNDG. AS WE ROLLED OUT OF THE TURN, THE LNDG AREA I SPOTTED WAS A LARGE SANDBANK ALONG THE RIVER. I MADE ONE MAYDAY CALL ON THE UNICOM FREQ THAT I WAS MONITORING WITH NO REPLY. I THEN XMITTED A MAYDAY CALL ON 121.5 PRIOR TO MAKING THE FORCED LNDG, WHILE EXPEDITING NORMAL EMER PROCS. I USED WHAT LITTLE PWR I HAD TO MAKE IT TO MY LNDG DEST AND AS IT WAS TO BE SAND, A SOFT FIELD LNDG WAS APPROPRIATE. THE ENG HAD 2 PWR SURGES PRIOR TO LNDG. A SAFE FORCED LNDG WAS ACCOMPLISHED WITH SLIGHT DAMAGE TO THE PROP. MOISTURE IN THE AIR MIGHT HAVE PROVIDED CARB ICING, HOWEVER BECAUSE OF THE LARGE PWR LOSS, I BELIEVE THAT THE CAUSE WAS FUEL RELATED. HOWEVER, POST INCIDENT INSPECTION REVEALED NO FUEL CONTAMINATION OR PROBLEMS. IT SEEMS RATHER A MYSTERY.

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