GOLDEN, CO, USA
N7411N
HILLER UH-12E
THE INSTRUCTOR (CFI) & DUAL STUDENT WERE PRACTICING PINNACLE APCHS. THE CFI WAS FLYING THE HELICOPETER AS AN APCH WAS MADE TO A 6318' PINNACLE FROM THE SOUTHEAST. ACCORDING TO THE STUDENT, THE WIND WAS FROM THE EAST AT 8 TO 10 KTS. AS THE CFI FLEW TO A 4' HOVER, THERE WAS A LOSS OF TAIL ROTOR CONTROL & THE HELICOPTER BEGAN AN UNCOMMANDED RIGHT TURN. THE CFI MADE A HOVERING AUTOROTATION, BUT THE HELICOPTER TOUCHED DOWN ON AN OUTCROPPING OF ROCK & ROCKED BACKWARD. SUBSEQUENTLY, THE TAIL STINGER & TAIL ROTOR BLADES STRUCK THE TERRAIN & THE HELICOPTER WAS DAMAGED. LATER, THE CFI SAID HE BELIEVED THE TAIL ROTOR CONTROL CABLES HAD UNSPOOLED FROM THE DRUM & RESULTED IN THE LOSS OF CONTROL. HOWEVER, A POST-ACDNT EXAM FAILED TO REVEAL EVIDENCE OF A PRE-ACDNT FAILURE OR MALFUNCTION. DENSITY ALT WAS APRX 8600'. APRX 7 MIEAST AT JEFFCO ARPT, THE WIND WAS FROM 140 DEG AT 10 KTS.
IMPROPER IN-FLIGHT PLANNING/DECISION BY THE CFI WHICH RESULTED IN LOSS OF TAIL ROTOR EFFECTIVENESS AND LOSS OF DIRECTIONAL CONTROL. CONTRIBUTING FACTORS WERE HIGH DENSITY ALTITUDE, TAILWIND, AND ROUGH/UNEVEN TERRAIN.
Source: NTSB Aviation Accident Database
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