PVT PLT ON CONVENTIONAL GEAR ACFT CHK OUT PULLS FUEL SHUTOFF TO 'OFF' INSTEAD OF CARB HEAT 'ON.' ENG FAILURE ON TKOF.

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ACFT: SMA TAIL DRAGGER. INSTRUCTOR 14000 HR ATP. STUDENT 1195 HR PRIVATE PLT. INSTRUCTIONAL FLT TO PROVIDE RECURRENT TRAINING IN SMA ACFT. STUDENT PLT HAD PREVIOUSLY CHKED OUT IN THIS TYPE ACFT AT NEARBY ARPT. AFTER PREFLT BRIEFING; FLT DEPARTED HVN TO AN AREA OUTSIDE THE ATA FOR AIR WORK. AFTER APPROX 20 MINS; FLT RETURNED TO HVN TO PRACTICE TKOF AND LNDGS. 2 NORMAL LNDGS (FULL STALL; 3 POINT) WERE ACCOMPLISHED. ON DOWNWIND FOR 3RD LNDG; INSTRUCTOR REMINDED STUDENT TO APPLY CARB HEAT PRIOR TO REDUCING PWR. STUDENT HAD DONE SO PROPERLY ON 2 PREVIOUS LNDGS BUT APPARENTLY FORGOT TO DO SO ON 3RD LNDG. 3RD LNDG WAS NORMAL; BUT AT APPROX 250 FT AGL AFTER TKOF; THE ENG FAILED. INSTRUCTOR ASSUMED CTL OF ACFT AT THAT TIME. AT THE POINT OF ENG FAILURE; ONLY 800-900 FT OF RWY REMAINED. WITH NO SUITABLE FORCED LNDG SITE AVAILABLE BEYOND THE ARPT BOUNDARY (HOUSES; PWRLINES; HWY; ETC); INSTRUCTOR SLIPPED ACFT TO MAX AMOUNT POSSIBLE IN AN EFFORT TO LAND ON REMAINING RWY. ACFT TOUCHED DOWN IN A DISPLACED THRESHOLD AREA WITH APPROX 200 FT OF ASPHALT REMAINING. ACFT RAN OFF THE END OF RWY INTO A GRASSY AREA; WHERE INSTRUCTOR INTENTIONALLY GND-LOOPED THE ACFT TO AVOID HITTING THE ARPT SECURITY FENCE. ACFT HAD STRUCK A FRANGIBLE RWY LIGHT UPON LEAVING THE ASPHALT RWY; BREAKING THE LIGHT AND CAUSING A 6 INCH RIP IN THE FABRIC OF THE L MAIN GEAR FAIRING. NO FURTHER DAMAGE WAS DONE. THE ACFT WAS NOT DAMAGED IN ANY WAY BY THE INTENTIONAL GND-LOOP. NEITHER OCCUPANT WAS INJURED. UPON INVESTIGATION IT WAS REVEALED THAT THE STUDENT PLT SITTING IN THE FRONT SEAT HAD PULLED THE FUEL SHUTOFF VALVE TO THE 'OFF' POSITION; INSTEAD OF PULLING THE CARB HEAT 'ON' AS INSTRUCTED BY THE INSTRUCTOR. THE FUEL SHUTOFF VALVE IS NOT READILY VISIBLE TO THE INSTRUCTOR SITTING IN THE BACK SEAT. THE CARB HEAT KNOB IS ALSO DIFFICULT FOR THE INSTRUCTOR TO SEE IF THE PERSON IN FRONT IS A RELATIVELY LARGE PERSON; AS THIS STUDENT WAS. UNFORTUNATELY; THE OP OF BOTH KNOBS IS A FORE AND AFT MOTION; AND COLORATION IS SIMILAR. HOWEVER; THE FUEL SHUTOFF VALVE ON THIS PARTICULAR ACFT IS QUITE STIFF; AND MUCH MORE DIFFICULT TO PULL THAN THE CARB HEAT CTL. MY OBSERVATION: A STUDENT WILL GO TO GREAT DIFFICULTY TO TRY TO KILL YOU. THE FACT THAT THE STUDENT HAD ACTIVATED THE CARB HEAT CTL PROPERLY DURING THE PREVIOUS 2 LNDGS; AND ALSO SEVERAL TIMES DURING THE AIR WORK PERIOD;ONLY MAKES IT MORE DIFFICULT TO UNDERSTAND THIS MENTAL LAPSE IN THIS CASE. FORTUNATELY THERE WAS JUST ENOUGH ROOM LEFT TO LAND THE ACFT AND AVOID A COMPLETE DISASTER; AND EVEN THE INTENTIONAL GND LOOP MANEUVER WORKED OUT MUCH BETTER THAN ONE WOULD EXPECT.