A C172 CFI WITH A STUDENT LAND LONG AND FAST WITH PWR STILL ON RESULTING IN THE ACFT SLIDING OFF THE END OF THE RWY AND A BLOWN TIRE.

Narrative

AFTER PRACTICING UNEVENTFUL TKOFS AND LNDGS AT OTTAWA ARPT; MY PRE-SOLO STUDENT AND I DEPARTED FOR OUR HOME FIELD AT JOHNSON COUNTY EXECUTIVE FOR A FULL STOP LNDG. WE WERE INSTRUCTED BY ATC TO ENTER A R DOWNWIND FOR RWY 18. AFTER NOTICING THAT WE WERE SLIGHTLY HIGH ON BASE; I CALLED FOR A PWR REDUCTION AND LOWERING OF THE NOSE. OUR DSCNT ANGLE WAS SLIGHTLY STEEP AND WE WERE GAINING SOME AIRSPD. AFTER FLARING ON THE CTRLINE OF THE RWY; WE FLOATED UNUSUALLY LONG AND EVENTUALLY TOUCHED DOWN. AS THE STUDENT APPLIED BRAKES THE TIRES STARTED TO SKID. IT WAS THEN THAT I REALIZED THAT THE THROTTLE WAS NOT ALL THE WAY BACK TO IDLE AND WE WERE ATTEMPTING TO STOP WITH PWR ON. I SUGGESTED A GAR; HOWEVER; THE STUDENT REMAINED ON THE BRAKES WITH THE TIRES SKIDDING. AT THIS MOMENT; I TOOK THE CTLS. DUE TO INSUFFICIENT RWY REMAINING; I REASSESSED THE SIT AND WITH THE THROTTLE FULLY OUT TO IDLE; I ATTEMPTED A TURN ONTO THE TXWY AT THE END OF THE RWY. OUR MOMENTUM WAS TOO FAST TO STOP; RESULTING IN A BLOWN TIRE AND THE ACFT SKIDDING ONTO THE GRASS. NO ADDITIONAL DAMAGE OCCURRED. THE PROPER CORRECTIVE ACTION COULD HAVE BEEN TO INITIATE A GAR AFTER MISSING THE FIRST 1/3 OF THE RWY.