JANESVILLE, WI, USA
N117M
MBB BK-117A-1
THE PILOT STATED THAT HE AND A COMPANY MECHANIC WERE IN CRUISE FLIGHT AT 2,000 FEET MSL ON A MAINTENANCE FLIGHT TEST, WHEN HE HEARD A NOISE, 'OBSERVED DEBRIS IN ALL DIRECTIONS FROM THE MAIN ROTOR...(AND) SEVERE VIBRATION WAS EXPERIENCED.' THE PILOT MADE AN EMERGENCY LANDING IN A SNOW-COVERED FIELD. POST-ACCIDENT EXAMINATION REVEALED THAT THE ENGINE COWLING ON THE LEFT SIDE OF THE AIRCRAFT HAD SEPARATED WHILE IN FLIGHT, CONTACTING AND DAMAGING THE MAIN ROTOR BLADES. SEVERAL PIECES OF THE SEPERATED COWLING WERE RECOVERED AND INSPECTED. THE LATCHES SHOWED NO MALFORMATION/STRETCHING, AND APPEARED TO BE CAPABLE OF NORMAL OPERATION.
THE PILOT-IN-COMMAND FAILED TO ENSURE THAT THE ENGINE COWLING LATCHES WERE PROPERLY SECURED PRIOR TO DEPARTING ON THE MAINTENANCE TEST FLIGHT; THE COWLING CAME LOOSE DURING FLIGHT, AND CONTACTED THE MAIN ROTOR BLADES BEFORE IT SEPARATED FROM THE HELICOPTER.
Source: NTSB Aviation Accident Database
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