NTSB Identification: NYC88IA186.
The docket is stored on NTSB microfiche number 40448.
Incident occurred Tuesday, July 12, 1988 in MANHATTAN, NY
Probable Cause Approval Date: 03/25/1991
Aircraft: MBB BK-117, registration: N135CP
Injuries: 1 Uninjured.

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

AS THE PLT OF AN S-76 HELICOPTER WAS HOVERING TO PARK NEXT TO A PARKED MBB BK 117 HELICOPTER, N135CP, THE MAIN ROTOR BLADES OF N135CP BEGAN FLAPPING. SUBSEQUENTLY, ONE BLADE FAILED FROM DOWNWARD OVERLOAD, ABOUT 29 INCHES FROM THE MAIN RETAINING PIN CENTER.

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

FAILURE OF THE MAIN ROTOR BLADE APPEARS TO BE THE RESULT OF A STATIC DOWNWARD BENDING OVERSTRESS, CAUSED BY ANOTHER HELICOPTER HOVERING OVER OR VERY CLOSE TO THE MAIN ROTOR BLADE AS IT WAS IN A STATIC/STOPPED POSITION.

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