Narrative:

Engine stopped, made off airport landing, amount of fuel was marginal, 1 1/2 inches in right tank, left tank empty -- checked after emergency landing. Student had preflted plane when I arrived at the beginning of lesson, student indicated tanks were 1/2 full and that plane had been flown earlier. We proceeded to practice area for slow flight, then to L39 for touch-and-goes. On departing L39 for return to see student reported an engine sputter. I did not notice it. I did note gas gauge reading showing left tank empty and almost 1/4 tank in right tank. Problem caused by 1 of the tanks running empty before the other 1 and letting air in the system. This was new information to me. I thought if 1 had gas in 1 tank it would run into the engine. Not true. You have to have gas in both tanks when they are tied together.

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Original NASA ASRS Text

Title: EMER OFF ARPT LNDG PERFORMED BY INSTRUCTOR PLT ON A TRAINING FLT AFTER ENG CUTS OUT DUE TO FUEL STARVATION EXHAUSTION.

Narrative: ENG STOPPED, MADE OFF ARPT LNDG, AMOUNT OF FUEL WAS MARGINAL, 1 1/2 INCHES IN R TANK, L TANK EMPTY -- CHKED AFTER EMER LNDG. STUDENT HAD PREFLTED PLANE WHEN I ARRIVED AT THE BEGINNING OF LESSON, STUDENT INDICATED TANKS WERE 1/2 FULL AND THAT PLANE HAD BEEN FLOWN EARLIER. WE PROCEEDED TO PRACTICE AREA FOR SLOW FLT, THEN TO L39 FOR TOUCH-AND-GOES. ON DEPARTING L39 FOR RETURN TO SEE STUDENT RPTED AN ENG SPUTTER. I DID NOT NOTICE IT. I DID NOTE GAS GAUGE READING SHOWING L TANK EMPTY AND ALMOST 1/4 TANK IN R TANK. PROBLEM CAUSED BY 1 OF THE TANKS RUNNING EMPTY BEFORE THE OTHER 1 AND LETTING AIR IN THE SYS. THIS WAS NEW INFO TO ME. I THOUGHT IF 1 HAD GAS IN 1 TANK IT WOULD RUN INTO THE ENG. NOT TRUE. YOU HAVE TO HAVE GAS IN BOTH TANKS WHEN THEY ARE TIED TOGETHER.

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.