NTSB Identification: LAX04IA133.
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Nonscheduled 14 CFR
Incident occurred Thursday, February 19, 2004 in Las Vegas, NV
Probable Cause Approval Date: 01/31/2006
Aircraft: Eurocopter AS 350B, registration: N358NT
Injuries: 6 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.
The helicopter experienced an in-flight loss of tail rotor control due to the fatigue fracture and failure of the tail rotor pitch change lever (SN MA 3671). The purpose of this part is to translate forward and aft movement from the tail rotor controls to change the pitch of the tail rotor. The operator had removed the component from the helicopter prior to the arrival of Federal Aviation Administration inspectors, and so the condition of the part as installed could not be determined. Following the incident, the operator discovered a crack on an additional lever (SN MA 3010) in their fleet. The Safety Board Materials Laboratory determined that the fatigue cracks in the two levers were not due to material or manufacturing defects, but were caused by improper installation of the component on the tail rotor gear box. Service Bulletin (SB) No. 65.00.42 was issued in response to cracks found in other levers where the cracks were determined to have been caused by improper installation of the tail rotor gear box pitch control lever bolt. The condition of the incident lever and the second one were found to be identical to the prior cases that triggered the issuance of the service bulletin. The tail rotor gearbox assembly had 3,148.5 hours. The lever is an on-condition part, which is inspected during overhaul of the tail rotor gear box. The overhauls are completed at a normal interval of 3,000 hours; the manufacturer allows a tolerance of 10 percent over the recommended overhaul schedule. When the tail rotor gearbox assembly was submitted for overhaul, a tail rotor pitch change lever different from the one involved in the incident was submitted for inspection. There are no tracking requirements on this part and the time and history of the tail rotor pitch change lever involved in the incident could not be determined.
The National Transportation Safety Board determines the probable cause(s) of this incident to be: the tail rotor pitch change lever failed in fatigue due to improper installation by company maintenance personnel. Full narrative available
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