NTSB Identification: CEN09LA198
14 CFR Part 91: General Aviation
Accident occurred Monday, March 02, 2009 in Galliano, LA
Probable Cause Approval Date: 07/28/2009
Aircraft: BELL 206, registration: N410RL
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 commercial pilot was starting the single-engine helicopter's engine when he heard a loud bang and vibration. He immediately shut down the engine and exited the helicopter. Examination of the helicopter revealed that the tail rotor driveshaft and coupling had severed just forward of the gearbox, which resulted in substantial damage to the tail boom. The helicopter had undergone recent maintenance to the tail rotor gearbox input seal which included the removal of the tail rotor drive shaft from the coupling. When the two components were reattached, the mechanic only hand-tightened the bolts, figuring additional maintenance was still planned for the gearbox. He then installed the tail rotor drive shaft shaft cover. The mechanic moved on to another project and did not make a logbook entry of the work that he had completed or that the bolts were only hand-tightened. Another mechanic later performed additional maintenance to the gearbox, but the bolts were not checked since the maintenance manual did not require the removal of the tail rotor driveshaft cover. A .2-hour maintenance flight check was conducted and the helicopter was returned to service. The accident occurred on first engine start after it had been returned to service.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: The failure of the tail rotor driveshaft and coupling during engine start due to the mechanic's failure to properly reattach the tail rotor driveshaft and coupling during maintenance. Full narrative available
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