NTSB Identification: NYC04FA197.
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Accident occurred Sunday, August 29, 2004 in Northport, NY
Probable Cause Approval Date: 04/25/2006
Aircraft: Robinson R-22, registration: N871CL
Injuries: 2 Fatal.

NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.

The flight instructor and the pilot departed on an instructional flight, and about 45 minutes later, witnesses observed the helicopter flying along a beach between 100 and 200 feet agl. One witness reported that the helicopter contacted a kite. Immediately thereafter, witnesses heard a loud "cracking" or "popping" noise, and the main rotor separated. The helicopter subsequently entered an uncontrolled descent and impacted the water. Examination of the main rotor mast fracture surfaces revealed signatures consistent with overload. The cockpit also exhibited damage consistent with main rotor contact. No evidence of any pre-impact mechanical malfunction or failure was noted. According to the pilot's operating handbook for the helicopter, "Pushing the cyclic forward following a pull-up or rapid climb, or even from level flight, produces a low-G (weightless) flight condition..." and "...mast bumping can occur. Severe in-flight mast bumping usually results in main rotor shaft separation and/or rotor blade contact with the fuselage."

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

An improper maneuver by the flightcrew while attempting to avoid a kite, which resulted in mast bumping, the separation of the main rotor system, and a subsequent uncontrolled descent into water.

Full narrative available

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