Aviation Accident Summaries

Aviation Accident Summary LAX88FA140

FREMONT, CA, USA

Aircraft #1

N5692P

ENSTROM 280C

Analysis

WHILE WORKING IN THE TRAFFIC PATTERN ON A LOCAL INSTRUCTIONAL FLIGHT, THE CFI NOTICED THE MAIN ROTOR RPM WAS BELOW THE GREEN ARC. HE ENTERED AN AUTOROTATION AND TRIED UNSUCCESSFULLY TO GET THE ROTOR RPM BACK INTO THE GREEN ARC. THE HELICOPTER COLLIDED WITH THE GROUND DURING THE ATTEMPTED AUTOROTATION WITH A LOW MAIN ROTOR SPEED. INVESTIGATION REVEALED THAT THE ENGINE DRIVE PULLEY WAS WORN BEYOND THE FACTORY ESTABLISHED LIMIT, WHICH ALLOWED THE DRIVE BELT TO SLIP. THE MINIMUM SERVICEABLE WEAR LIMIT FOR THE DRIVE PULLEY WAS NOT PUBLISHED IN THE FACTORY MAINTENANCE PROCEDURES.

Probable Cause and Findings

FAILURE OF THE ENGINE TO MAIN ROTOR DRIVE SYSTEM DUE TO A DRIVE BELT SLIPPAGE CAUSED BY A DRIVE PULLEY WORN BEYOND ITS SERVICE LIMIT. CONTRIBUTING TO THE ACCIDENT WAS THE INADEQUATE FACTORY MAINTENANCE MANUALS WHICH DID NOT PROVIDE THE SERVICEABLE LIMITS FOR THE DRIVE BELT PULLEYS.

 

Source: NTSB Aviation Accident Database

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