AN SMA INSTRUCTOR PLT RAN A FUEL TANK DRY AND LANDED IN A CORN FIELD. HE CHANGED TO ANOTHER TANK; RAN UP THE ENG; AND RETURNED TO HIS HOME BASE.

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SMA FUEL EXHAUSTION FORCED LNDG FROM 800 FT AGL. I WAS CHKING A NEW PRIVATE PLT OUT IN HER HUSBAND'S SMA. I DID NOT PREFLT THE PLANE; BUT DID LOOK IN THE MAIN TANKS. LOOKING IN THE TANKS; I COULD SEE THE FUEL WAS DOWN 2-3 INCHES. AT THAT POINT THE ENG QUIT. I HAD THE PLT SWITCH TANKS AND START DUMPING THE WOBBLE PUMP. WHEN THE ENG STILL DIDN'T RESTART AND WE CONFIRMED THE GEAR WAS DOWN WE HAD NO CHOICE BUT TO FLARE AND LAND. AFTER STOPPING THE ENG WAS RUNNING. THE FUEL WAS NOW ON THE L TANK AND THE GAUGE SHOWED OVER 1/2 FULL. TAXIED TO THE END OF THE FIELD. TESTED IT AGAIN AT FULL PWR; AND DECIDED IT WAS SAFE TO TKOF. THE MECH FOUND THE R BLADDER HAS A RIDGE BUCKLED UP FROM THE BOTTOM HOLDING THE SENDER FLOAT UP AND TRAPPING FUEL. A LOOSE CONNECTION GAVE FALSE FUEL LEVEL READINGS. HOW PROBLEM AROSE; CONTRIBUTING FACTORS; THIS SITUATION HAD THE CLASSIC CHAIN OF EVENTS WHICH LED TO THE ENG FAILURE; AND COULD HAVE BEEN AVOIDED AT ANY POINT IN THE CHAIN. I WAS CHKING OUT MY WIFE (NEW PLT) IN THE PLANE. THE ACFT WAS FLOWN 1:15 MINS ON MM/DD/92 AND WAS NOT REFUELED BECAUSE THE FBO WAS OUT OF FUEL. THE ACFT WAS ANNUALED; THEN TEST FLOWN ON MM/DD/92 AND WAS NOT REFUELED AGAIN BECAUSE THE FBO WAS OUT OF FUEL; (THE SECOND TIME). THIS IS UNUSUAL FOR THIS FBO. VISUAL INSPECTION OF THE FUEL BY MYSELF (CFI) SHOWED THE FUEL IN THE MAINS TO BE DOWN 2-3 INCHES. MISUNDERSTANDING BTWN THE HUSBAND; WIFE (OWNERS) AND CFI ABOUT HOW OFTEN THE PLANE WAS FLOWN SINCE THE LAST FILL-UP; AND HOW MUCH TIME REMAINED IN EACH TANK. MISUNDERSTANDING/POOR COMS ENRTE ON WHICH TANK TO CRUISE ON. SAME PROBLEM SWITCHING TANKS ENTERING THE PATTERN; AND AGAIN ON TKOF. AN INTERCOM WAS NORMALLY USED EXCEPT ON THIS FLT. IT WAS NOT IN THE PLANE AFTER THE ANNUAL INSPECTION. FAILURE OF THE CFI (MYSELF) TO VISUALLY CONFIRM WHICH TANK WE HAD SWITCHED TO BECAUSE THE SELECTOR IS LOCATED UNDER HER L THIGH AND CANNOT BE SEEN BY THE PLT IN THE R SEAT WITHOUT UNBUCKLING THE SEAT BELT AND GETTING UP OUT OF THE SEAT. AN INSPECTION OF THE EXHAUSTED TANK'S BLADDER AND SENDING UNIT SHOWED THE BLADDER BUCKLED UP 1 1/4 INCH WHICH HELD THE FLOAT UP AND PERHAPS TRAPPED SOME FUEL BEHIND THE RIDGE; AND A LOOSE/POOR CONNECTION ON THE FUEL SENDER CAUSED THE GAUGE TO SHOW OVER HALF FULL. I HAVE MADE A FUEL DIPSTICK FOR MANY OF THE PLANES THAT I FLY REGULARLY BY DRAINING THE TANK; AND ADDING 2 GALLONS AT A TIME; AND MARKING THE STICK UNTIL THE TANK IS FULL. THIS PLANE DOES NOT HAVE ONE YET. I BELIEVE THIS SHOULD BE PROVIDED FOR ALL TYPES OF ACFT AND I HAVE ALWAYS BEEN AMAZED THAT THE MANUFACTURER DOES NOT MAKE ONE. OF THE 65 DIFFERENT MODELS-TYPES OF PLANES I'VE FLOWN IN THE PAST 15 YRS; THE ONLY PLANE I'VE SEEN WITH A DIPSTICK PROVIDED BY THE MANUFACTURER WAS A NEW SMA PLANE.