NTSB Identification: CHI91LA097.
The docket is stored on NTSB microfiche number 43088.
Accident occurred Wednesday, February 20, 1991 in NORTH MANKATO, MN
Probable Cause Approval Date: 10/08/1992
Aircraft: HUGHES 269C, registration: N8955F
Injuries: 2 Serious,1 Minor.

NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

THE PILOT REPORTED THAT DURING THE AERIAL OBSERVATION FLIGHT HE HEARD A LOUD NOISE FROM THE BACK OF THE HELICOPTER. THE HELICOPTER THEN BEGAN ROTATING CLOCKWISE AND DESCENDED TO IMPACT WITH THE TERRAIN IN A WOODED AREA. POST ACCIDENT IMSPECTION REVEALED A FATIGUE FAILURE OF THE TAIL BOOM SUPPORT STRUT CLUSTER FITTING (LEFT SIDE). AN AIRWORTHINESS DIRECTIVE ISSUED IN 1976 CALLED FOR A DAILY VISUAL INSPECTION AND A 200 HOUR DYE PENETRANT INSPECTION OF THE FITTING. A LOGBOOK ENTRY DATE AUGUST 15, 1990, STATED ALL AD'S HAD BEEN COMPLIED WITH.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

THE FATIQUE FAILURE OF THE TAIL BOOM SUPPORT STRUT ATTACHMENT CLUSTER AND THE IMPROPER INSPECTION OF THE CLUSTER ATTACHMENT.

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