Narrative:

On the morning of 01/xx/90, I was conducting a flight lesson at 2500' MSL. (Note: prior to flight, I conducted a normal preflight inspection [demonstrated for student's first flight, including draining each wing sump twice and draining fuel sump/engine twice. Fuel level indicated half tanks each side. No water or contamination.) executing medium turns, turns to a heading, and climbing turns and dscnts, approximately 50 mins into the flight, I had my student performing a descending turn to an assigned heading. Power was reduced to 2000 RPM and a cruise descent was made to an altitude of 2000' MSL. I then instructed my student to increase power to full power and climb back up to 2500'. As he applied full throttle I noticed no increase in engine power and the engine began to run rough. (Note: at the full power setting I was only able to maintain 2000 RPM.) I immediately applied carburetor heat and took command of the aircraft and leveled out at approximately 2300' (radio contact with columbus approach was initiated 14 mi northeast of practice area). As I applied carburetor heat I noticed a normal reduction in RPM's, indicating that heat was being applied to the carburetor inlet. The engine can't run rough and I noticed I was slowly losing RPM's. Now was down to 1500-1600 RPM's and altitude approximately 1800' MSL and descending. (Note: throttles position was still at full power.) engine roughness now became more acute and I reduced the throttle/power setting (approximately 1') and an increase of 300 RPM was indicated. RPM's now stabilized at 1800 RPM. Any increase I made in the throttle setting brought back acute engine roughness and further loss in RPM's. I then proceeded to execute the emergency procedures checklist. As I proceeded through the checklist I pushed the carburetor heat back in and gained an additional 75-100 RPM's. (Engine now running slightly rough, and RPM's fluctuating between 1800 and 1950.) my altitude was now down to approximately 1500' and I was working with columbus approach on obtaining a landing site when the engine suddenly began to run acutely rough again and RPM's fell to approximately 1100'. Unable to gain any power over 1100 RPM's, I executed the emergency landing checklist told columbus approach I was unable to make the field and selected a suitable field and set the aircraft down with no damage to the aircraft or persons aboard. Conclusion: after landing a fuel sample was taken from the left wing sump and a small amount of water was found. Investigators assumed due to the intense cold WX in the area, water in the left tank had frozen, sow when a fuel sample was taken prior to flight, no water contamination had shown. While in flight, the ice in the left tank broke up/crystals and was able to work its way into the fuel line, partially blocking fuel flow and crystal/water that was in the line melted, contaminating fuel flow.

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Original NASA ASRS Text

Title: INSTRUCTOR AND STUDENT ON FIRST FLT LESSON EXPERIENCE ENGINE ROUGHNESS AND POWER LOSS ON SMA, FORCED LNDG RESULTS.

Narrative: ON THE MORNING OF 01/XX/90, I WAS CONDUCTING A FLT LESSON AT 2500' MSL. (NOTE: PRIOR TO FLT, I CONDUCTED A NORMAL PREFLT INSPECTION [DEMONSTRATED FOR STUDENT'S FIRST FLT, INCLUDING DRAINING EACH WING SUMP TWICE AND DRAINING FUEL SUMP/ENG TWICE. FUEL LEVEL INDICATED HALF TANKS EACH SIDE. NO WATER OR CONTAMINATION.) EXECUTING MEDIUM TURNS, TURNS TO A HDG, AND CLBING TURNS AND DSCNTS, APPROX 50 MINS INTO THE FLT, I HAD MY STUDENT PERFORMING A DSNDING TURN TO AN ASSIGNED HDG. PWR WAS REDUCED TO 2000 RPM AND A CRUISE DSCNT WAS MADE TO AN ALT OF 2000' MSL. I THEN INSTRUCTED MY STUDENT TO INCREASE PWR TO FULL PWR AND CLB BACK UP TO 2500'. AS HE APPLIED FULL THROTTLE I NOTICED NO INCREASE IN ENG PWR AND THE ENG BEGAN TO RUN ROUGH. (NOTE: AT THE FULL PWR SETTING I WAS ONLY ABLE TO MAINTAIN 2000 RPM.) I IMMEDIATELY APPLIED CARB HEAT AND TOOK COMMAND OF THE ACFT AND LEVELED OUT AT APPROX 2300' (RADIO CONTACT WITH COLUMBUS APCH WAS INITIATED 14 MI NE OF PRACTICE AREA). AS I APPLIED CARB HEAT I NOTICED A NORMAL REDUCTION IN RPM'S, INDICATING THAT HEAT WAS BEING APPLIED TO THE CARB INLET. THE ENG CAN'T RUN ROUGH AND I NOTICED I WAS SLOWLY LOSING RPM'S. NOW WAS DOWN TO 1500-1600 RPM'S AND ALT APPROX 1800' MSL AND DSNDING. (NOTE: THROTTLES POS WAS STILL AT FULL PWR.) ENG ROUGHNESS NOW BECAME MORE ACUTE AND I REDUCED THE THROTTLE/POWER SETTING (APPROX 1') AND AN INCREASE OF 300 RPM WAS INDICATED. RPM'S NOW STABILIZED AT 1800 RPM. ANY INCREASE I MADE IN THE THROTTLE SETTING BROUGHT BACK ACUTE ENG ROUGHNESS AND FURTHER LOSS IN RPM'S. I THEN PROCEEDED TO EXECUTE THE EMER PROCS CHKLIST. AS I PROCEEDED THROUGH THE CHKLIST I PUSHED THE CARB HEAT BACK IN AND GAINED AN ADDITIONAL 75-100 RPM'S. (ENG NOW RUNNING SLIGHTLY ROUGH, AND RPM'S FLUCTUATING BTWN 1800 AND 1950.) MY ALT WAS NOW DOWN TO APPROX 1500' AND I WAS WORKING WITH COLUMBUS APCH ON OBTAINING A LNDG SITE WHEN THE ENG SUDDENLY BEGAN TO RUN ACUTELY ROUGH AGAIN AND RPM'S FELL TO APPROX 1100'. UNABLE TO GAIN ANY PWR OVER 1100 RPM'S, I EXECUTED THE EMER LNDG CHKLIST TOLD COLUMBUS APCH I WAS UNABLE TO MAKE THE FIELD AND SELECTED A SUITABLE FIELD AND SET THE ACFT DOWN WITH NO DAMAGE TO THE ACFT OR PERSONS ABOARD. CONCLUSION: AFTER LNDG A FUEL SAMPLE WAS TAKEN FROM THE LEFT WING SUMP AND A SMALL AMOUNT OF WATER WAS FOUND. INVESTIGATORS ASSUMED DUE TO THE INTENSE COLD WX IN THE AREA, WATER IN THE LEFT TANK HAD FROZEN, SOW WHEN A FUEL SAMPLE WAS TAKEN PRIOR TO FLT, NO WATER CONTAMINATION HAD SHOWN. WHILE IN FLT, THE ICE IN THE LEFT TANK BROKE UP/CRYSTALS AND WAS ABLE TO WORK ITS WAY INTO THE FUEL LINE, PARTIALLY BLOCKING FUEL FLOW AND CRYSTAL/WATER THAT WAS IN THE LINE MELTED, CONTAMINATING FUEL FLOW.

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.