NTSB Identification: LAX96LA207.
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Accident occurred Tuesday, May 28, 1996 in THERMAL, CA
Probable Cause Approval Date: 08/20/1996
Aircraft: McDonnell Douglas MD-600, registration: N600RN
Injuries: 1 Uninjured.

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 flight was part of an engineering test flight series to complete the Part 27 certification for a new rotorcraft. The specific test point was part of a flight strain survey and involved cyclic control reversals. The pilot had set the parameters and executed the cyclic control inputs as planned. Almost simultaneous with the aft movement of the cyclic there was a loud noise and immediate vibrations in the aircraft and the controls. A pilot in the chase aircraft informed the pilot that a main rotor blade had struck and severed the tail boom. A power off autorotation was accomplished without the tail rotor system. The resultant hard landing was onto a pile of dry brush which was ignited by the hot engine exhaust. The brush fire destroyed the aircraft.

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

inadequate design of the stress limits for cyclic control of the helicopter.

Full narrative available

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