Aviation Accident Summary LAX91LA249

HURON, CA, USA

Aircraft #1

N507HA

HILLER UH-12E

Analysis

THE PILOT COMPLETED AN AERIAL APPLICATION FLIGHT AND WAS RETURNING TO THE LOADING AREA WHEN THE HELICOPTER SUSTAINED A TOTAL LOSS OF POWER. DURING THE SUBSEQUENT AUTOROTATION THE PILOT ATTEMPTED TO SIDESLIP THE HELICOPTER BETWEEN THE ALMOND TREES BUT WAS UNABLE TO DO SO. THE ENGINE AND SUBSEQUENT METALLURGICAL EXAMINATION DISCLOSED THE NO. 3 CYLINDER CONNECTING ROD BOLT FAILED DUE TO FATIGUE. COMPANY MAINTENANCE PERSONNEL REPORTED THAT THE FATIGUE WAS CAUSED BY CONSISTENT ENGINE OVERSPEED POWER SETTINGS BY THE PILOTS FLYING THE HELICOPTER.

Probable Cause and Findings

THAT UNKNOWN PILOT(S) IMPOPERLY USED THE THROTTLE CONTROL WHICH CAUSED AN OVERSPEED CONDITION. CONTRIBUTING TO THIS ACCIDENT WAS THE CONNECTING ROD BOLT FATIGUE FAILURE.

 

Source: NTSB Aviation Accident Database

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