CASTROVILLE, CA, USA
N5374V
HILLER UH12E
THE ACFT LANDED HARD AND ROLLED OVER AFTER THE LNDG SKID FAILED IN A FORCED LNDG. THE PLT SAID HE WAS CRUSING AT 500 FT AGL OVER AN OPEN FIELD WHEN HE HEARD A LOUD BANG. THE HELICOPTER BEGAN TO VIBRATE SEVERELY AND SPIRAL TO THE RIGHT. THE PLT LOST GROUND REFERENCE IN THE PRE-DAWN DARKNESS WHEN HE TURNED ON THE LIGHTS. NOT WANTING TO LAND TOO HARD HE ELECTED TO LEAVE THE ENG RUNNING AND NOT AUTO-ROTATE. INVESTIGATION INDICATED THAT ONE TAIL ROTOR BLADE HAD SEPARATED AT THE TENSION TORSION STRAP ATTACH BOLT HOLE. THIS IS THE TRANSITION AREA WHERE THE BLADE ROOT CASTING AND SHEET METAL BLADE SKIN ARE JOINED. THE FRACTURE SURFACE OF THE CASTING APPEARED TO BE OVERLOADED WITH NO APPARENT INDICATION OF FATIGUE. THE OUTBOARD BLADE SECTION SHOWED NO INDICATION OF FOREIGN OBJECT CONTACT. ALL COMPONENTS OF THE HELICOPTER WERE LOCATED IN THE IMPACT AREA EXCEPT ONE TAIL ROTOR BLADE.
Source: NTSB Aviation Accident Database
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