NTSB Identification: CEN09IA032
14 CFR Part 91: General Aviation
Incident occurred Sunday, October 19, 2008 in Amherst, TX
Probable Cause Approval Date: 08/13/2009
Aircraft: MD Helicopter Inc MD 900, registration: N902NM
Injuries: 4 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.

While in cruise flight, the helicopter experienced a hard right yaw and subsequent pitching moment up and down. The pilot was able to regain control of the helicopter and land without further incident. Examination revealed that the left vertical stabilizer control system adapter had failed. Metallurgical examination revealed that the failure mode was reverse bending fatigue. The vertical stabilizer control system adapter has been replaced with an improved design. Further, the Federal Aviation Administration has issued an Airworthiness Directive (AD) requiring all MD900 helicopter operators with the old VSCS tube adapters to comply with airspeed and autopilot restrictions. If an operator replaces the old VSCS tube adapter with the new design, the AD is not applicable.

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

The failure of the vertical stabilizer control adapter due to reverse bending fatigue.

Full narrative available

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