GLIDER TOW PLT OF PA25 STARTS FULL POWER TKOF ROLL WHILE LINE TO GLIDER IS STILL SLACK. SUBSEQUENT EMERGENCY BRAKING CAUSES TOW PLANE TO NOSE OVER DAMAGING PROP; ENGINE AND TOW APPARATUS.

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AS A TOW PLT FOR A GLIDERPORT; I WAS PREPARING FOR THE 8TH LAUNCH OF A FAIRLY BUSY AFTERNOON. THE TOW ROPE (ABOUT 200 FT) NORMALLY REMAINED ATTACHED TO THE TOW PLANE THROUGH ALL PHASES OF THE OP. FOR EFFICIENCY; I HAD TAXIED THE TOW PLANE TO POS THE GLIDER'S END OF THE TOW ROPE WITHIN EASY REACH FOR HOOK-UP TO THE GLIDER. I THEN TAXIED FORWARD; LINING UP IN FRONT OF THE GLIDER AND POSITIONING THE TOW PLANE FAR ENOUGH AWAY TO MINIMIZE THE PROP WASH BLOWING THE 2 MEN WHO WOULD BE IN THE GLIDER. IT APPEARED THAT THE 'RIDE PLT' WAS ASSISTING THE CUSTOMER GETTING SETTLED INTO THE FRONT SEAT. I LEFT A SIGNIFICANT AMOUNT OF SLACK IN THE ROPE TO ALLOW FOR GLIDER HOOK-UP AND/OR TO PRECLUDE MOVING THE GLIDER FORWARD BEFORE THEY WERE IN AND READY. I THEN OCCUPIED MYSELF WITH THE PRETKOF CHKLIST. A FEW MINS LATER I SAW IN THE TOW PLANE'S MIRROR THAT THE GLIDER'S CANOPY WAS CLOSING AND THE WING WAS BEING RAISED BY THE 'WING RUNNER.' THE WING RUNNER WAS A BOY LOOKING TO BE 8-10 YRS OLD. HE ACTED UNCERTAIN; CONFIRMING TO ME THAT I WOULD RELY ON SIGNALS FROM THE GLIDER; NOT JUST HIM. THE RUDDER ON THE GLIDER FANNED A FEW TIMES AND THE BOY CONFIRMED WITH THE CIRCULAR WAVE 'LAUNCH' SIGNAL. I QUICKLY SCANNED THE PATTERN AND RWY FOR CONFLICTS AND RESPONDED BY FANNING THE TOW PLANE RUDDER. THIS CONFIRMED THAT I WAS ABOUT TO TAKE OFF. I APPLIED FULL PWR AND CHKED THE ENG GAUGES. AS THE TOW PLANE ACCELERATED; I GLANCED AT THE GLIDER IN THE MIRROR. INSTEAD OF SEEING THE GLIDER'S START; I SAW THE ROPE QUICKLY MOVING AS THE REMAINING SLACK WAS TAKEN UP. I IMMEDIATELY PULLED THE THROTTLE BACK AND APPLIED THE BRAKES HEAVILY. THE NOSE PITCHED DOWNWARD AND THE PROP CUT INTO THE GRASS RWY. THE ENG STOPPED IN ABOUT 10-15 REVOLUTIONS. IN THE NEXT FEW MOMENTS; THE TAIL CAME BACK DOWN WITH A THUD. NO ONE WAS HURT. I WAS UNINJURED. I TURNED OFF THE ACFT'S ELECTRICAL SWITCHES; MAGNETOS AND SHUT OFF THE FUEL. I GOT OUT; GLANCED AT THE DAMAGE; AND WALKED BACK TO CHK THE PEOPLE IN THE GLIDER. THEY AND THE BOY WERE PHYSICALLY UNAFFECTED. SINCE THE TOW PLANE STOPPED BEFORE THE ROPE'S SLACK WAS ENTIRELY TAKEN UP; THE GLIDER NEVER MOVED. DAMAGE TO THE TOW PLANE: TO THE NAKED EYE; THE PROP WAS WORN AND 1 BLADE WAS BENT. ENG DAMAGE IS UNKNOWN AT THE TIME OF THIS WRITING. 2 LEAVES OF THE TAILWHEEL SPRINGS BROKE. THE 'TOST'-STYLE TAIL HOOK ASSEMBLY WAS BENT UPWARD; CONTACTING AND DAMAGING THE RUDDER. WHOSE FAULT: ALTHOUGH THE GLIDER PLT AND WING RUNNER HAD GIVEN THE SIGNAL TO TAKE OFF; THE RESPONSIBILITY TO ASSURE THE SLACK WAS REMOVED WAS CLRLY MINE. SOMEHOW I MISSED IT. WHY/WHAT WOULD HAVE HELPED? POSSIBLE CONTRIBUTING FACTORS: POOR SLEEP; HEAT-RELATED FATIGUE (APPROX 90 DEGS F); MODERATE DEHYDRATION; AND HUNGER. DIFFERENCES WHICH COULD HAVE PREVENTED OR MITIGATED THE EVENT: EXPERIENCED RELIABLE ASSISTANCE PERSONNEL (WING RUNNER). THE ADDITION OF A RED FUNNEL NEAR THE GLIDER'S END OF THE TOPE ROPE (THE RAISING OF THE FUNNEL OFF THE GND HAD BEEN A DEFINITE TELLTALE OF SLACK REMOVED WHEN USED IN THE PAST). BETTER LARGER NON-VIBRATING MIRRORS INSTALLED ON THE TOW PLANE. PLT HAND POSITIONED ON OR NEAR TOW ROPE RELEASE LEVER AFTER SETTING FULL PWR.