NTSB Identification: DFW05LA180.
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Nonscheduled 14 CFR
Accident occurred Monday, July 11, 2005 in
Probable Cause Approval Date: 02/28/2006
Aircraft: Bell 430, registration: N430CV
Injuries: 3 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 17,291-hour commercial helicopter pilot was on short final approach to a helipad on an offshore platform when he heard and felt a "bump" in the flight controls, followed by vibrations in the tail rotor pedals and a loss of tail rotor effectiveness. The pilot immediately landed the helicopter and preformed a normal engine cool-down. Inspection of the helipad found no evidence of a tail rotor strike. A post-accident inspection of the studs, that hold the tail rotor gearbox to the tail boom, revealed signs of low-cycle bending fatigue. Additional inspection under a microscope of the studs, showed evidence of high loads during bending. The 90-degree tail rotor gear-box teeth, displayed typical wear pattern and did not show any sign of misalignment. One of the tail-rotor blades was heavily damaged and missing a portion of the outer blade. The remaining end of the blade was slightly torn and contained gray paint or material at the leading edge. The material was later examined, and found to contain a high concentration of zinc. Examination of paint chips in the impact area on the vertical fin showed no zinc in the paint. The object that impacted the tail rotor blade could not be identified or located during the course of the investigation.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: The helicopter's tail rotor blade's contact with an unknown object during landing. Full narrative available
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