A HELI PLT DAMAGED HIS TAIL ROTOR.

Narrative

I WAS INSTRUCTING MR. X; A STUDENT FROM THE FBO. WE HAD LANDED ON RWY 3L AFTER PRACTICING PATTERN WORK. I RADIOED PRESCOTT TWR REQUESTING PERMISSION TO RELOCATE FROM 3L BACK TO FBO. THE TWR GRANTED PERMISSION TO CROSS RWY 3R; AND LAND BACK AT FBO. I INSTRUCTED MR. X TO PROCEED. HE LIFTED OFF VERTLY AND PROCEEDED DOWN RWY HDG; GAINING SPD AND ALT. TO MY SURPRISE; AT APPROX 7-10 FT; MR X APPLIED R CYCLIC; PUTTING US IN A DOWNWIND POS. THE WIND HAD BEEN OUT OF THE NW APPROX 17 TO 20 KTS; GUSTING TO 25 KTS; THUS PUTTING US IN AN ALMOST DIRECT XWIND DEPARTING ON RWY 3. AS I REACHED FOR THE CTLS ATTEMPTING TO RECOVER FROM MR X'S DOWNWIND TURN; I CONTINUED TO MY R TO COMPLETE A 270 DEG TURN BACK INTO THE WIND. AT APPROX 45 DEGS TO 90 DEGS; INTO THE TURN; I VISUALLY NOTICED ENG AND ROTOR RPM DECAYING FROM 3100 TO 2900 RPM AND DROPPING; EXPERIENCING PARTIAL ENG FAILURE. I RESPONDED BY LOWERING THE COLLECTIVE AND ADDING THROTTLE. THE ENG CONTINUED TO CUT OUT; NOT ALLOWING ADEQUATE ROTOR RPM. I REFED MY ROTOR RPM DECAY BELOW THE ALLOWABLE MINIMUM ROTOR RPM; AT WHICH POINT I EXECUTED AN AUTO ROTATION OVER THE IMMEDIATE AREA IN WHICH WE HAD ADVANCED BTWN RWY 3L AND RWY 3R; THUS PERFORMING A FORCED LNDG IN A ROCKY RAVINE. AS I WAS MAKING MY VERT DSCNT; IT WAS NECESSARY TO USE EXCESSIVE ACFT CYCLIC TO ZERO OUT MY AIRSPD DUE TO THE STRONG WINDS OUT OF THE NW. IN THE PROCESS OF FLARING THE HELI; MY TAIL ROTOR CAME IN CONTACT WITH THE ROCKS BELOW. AS WE CAME TO REST AT THE BOTTOM OF THE RAVINE; I RADIOED THE TWR TO NOTIFY THEM OF THE INCIDENT. THEY RESPONDED BY ASKING IF EVERYONE WAS ALRIGHT AND TOLD ME THEY HAD ALREADY SENT THE TRUCKS. I HAD A CHOICE OF PERFORMING A RUN-ON LNDG OR A VERT DSCNT. I CHOSE NOT TO DO A RUN-ON LNDG SIMPLY BECAUSE I RAN THE RISK OF ROLLING THE HELI DUE THE ROUGH TERRAIN WHICH MOST LIKELY WOULD HAVE CAUSED INJURY TO MY STUDENT AND MYSELF ALONG WITH DESTROYING THE HELI.