A C172 TRAINING FLT GOES OFF THE END OF A SHORT RWY WHILE CFI AND STUDENT ARE PRACTICING A SHORT FIELD TKOF AT 1K4; OK.

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MYSELF AND THE STUDENT PERFORMED MANEUVERS 2 MI S OF 1K4 (D J PERRY ARPT) AT 3500 FT MSL FOR 20 MINS. WE DECIDED TO PERFORM A SIMULATED ENG FAILURE OVER D J PERRY. ONCE WE KNEW WE HAD THE FIELD; WE DID A GAR FROM RWY 17. WHILE STAYING IN A L PATTERN FOR RWY 17; WE CAME BACK FOR A SHORT FIELD LNDG. ONCE WE HAD COME TO A FULL STOP; WE BACK TAXIED ON RWY 17 TO PERFORM A SHORT FIELD TKOF. WE FOLLOWED THE CHKLIST TO PERFORM A SHORT FIELD TKOF. ACCORDING TO THE POH; THE GND ROLL DISTANCE FOR THE ABOVE GIVEN WX CONDITIONS WAS 1300 FT AND THE TKOF DISTANCE FOR A 50 FT OBSTACLE CLRNC WAS 1720 FT. RWY 17/35 AT 1K4 ARPT IS 1803 FT LONG; THEREFORE; WE DECIDED TO PERFORM A SHORT FIELD TKOF. HOWEVER; WITH FULL TANKS AND INCREASING DENSITY ALT; THE ENG WAS UNABLE TO PRODUCE THE NEEDED PWR TO ACHIEVE THE ROTATION SPD OF 48 KTS. ON THE GND ROLL AFTER PASSING THE INTXN OF RWY 13/31 (REFER TO THE ARPT DIAGRAM) WE WERE AT 42 KTS. AT THIS POINT WE DECIDED TO ROTATE BECAUSE THERE WAS NOT ENOUGH RWY TO ABORT THE TKOF; THINKING THAT WE WOULD ACHIEVE THE SPD NEEDED IN GND EFFECT. UNFORTUNATELY AFTER ROTATION; THE STALL WARNING HORN SOUNDED AT ABOUT 10 FT. WE BROKE THE STALL; AND AT THIS POINT WE DID NOT HAVE ENOUGH DISTANCE TO CLB AND CLR THE OBSTACLES THAT WERE LOCATED AT THE DEP END OF RWY 17. THEREFORE; WE DECIDED TO CUT THE PWR; AND LAND THE PLANE. IN ADDITION; WE ALSO CUT THE MIXTURE IN ORDER TO STOP THE ENG TO AVOID DAMAGE TO THE PROP FROM THE GRAVEL NEAR THE GRASS. AT THIS POINT WE BELIEVED THAT THERE WAS SOME RWY AND HARD GRASS SURFACE TO STOP THE PLANE. UNFORTUNATELY; THE BRAKES DID NOT CATCH THE WET GRASS; CAUSING US TO SLIDE INTO THE PLOWED FIELD 200 FT S OF RWY 17. THE PLANE CAME TO REST ABOUT 10 FT INTO THE PLOWED FIELD ON A HDG OF 160 DEGS. WE PERFORMED THE EMER CHKLIST FOR SHUTTING THE ENG DOWN COMPLETELY AND THEN EXITED THE AIRPLANE. THERE WERE NO INJURIES; HOWEVER; THERE WAS MINOR DAMAGE TO THE NOSEWHEEL; DUE TO THE REMAINING INERTIA WHILE IT CAME TO A STOP IN THE PLOWED FIELD. WE UNDERSTAND THAT THIS INCIDENT WAS A RESULT OF POOR DECISION-MAKING. HOWEVER; WE DID WHAT WE BELIEVED WAS APPROPRIATE FOR THE GIVEN SIT. I DO NOT DOUBT MY OR THE STUDENT'S ABILITY TO MAKE THE RIGHT DECISION OR JUDGEMENT. I THINK WE DID A GOOD JOB IN MAKING THE CORRECT DECISION IN THE FEW SECONDS THAT WE HAD BEFORE THE INCIDENT OCCURRED. IN MY OPINION; IF WE HAD TRIED TO KEEP IT IN THE AIR THE OUTCOME PROBABLY WOULD HAVE BEEN MUCH WORSE. HOWEVER; WE DO AGREE THAT THERE WERE SOME ERRORS IN OUR JUDGEMENT. THE DENSITY ALT WAS SIGNIFICANTLY HIGHER THAN IT HAS BEEN IN THE LAST SEVERAL MONTHS KEEPING THE HIGH DENSITY ALT IN MIND; THE ONE THING THAT WE COULD HAVE DONE TO PRODUCE MORE PWR IS GND LEANED THE MIXTURE FOR TKOF. FINAL COMMENT: MANY INSTRUCTORS LIKE TO USE D J PERRY TO ADD REALISM TO FLT TRAINING. PERFORMING SHORT FIELD TKOFS AND LNDGS FROM A STRIP THAT IS A FEW THOUSAND FT DOES NOT GIVE THE SAME PERSPECTIVE AS PERFORMING THE SAME PROC OUT OF AN 1800 FT STRIP. I HAVE DONE SEVERAL TKOFS AND LNDGS ON RWY 17/35 AT D J PERRY IN THE PAST 4 1/2 YRS; BUT WHAT I SAW AND EXPERIENCE ON THE TKOF ROLL THIS DAY WAS UNUSUAL AND DIFFERENT.