Incident Overview
On March 2, 2009, at 0720 central daylight time, a Bell 206L-3 helicopter, registration N401RL, sustained damage when the tail rotor drive shaft and coupling severed while the aircraft was sitting on the ramp with the engine running. The helicopter was operated by and registered to Rotorcraft Leasing Company, LLC, of Broussard, Louisiana. The commercial pilot was not injured. Visual meteorological conditions prevailed and no flight plan was filed for the ferry flight conducted under 14 Code of Federal Regulations Part 91.
Sequence of Events
According to the operator, the pilot heard a loud bang and vibration shortly after starting the engine. He immediately shut down the engine and exited the helicopter. Examination revealed that the tail rotor drive shaft and coupling had severed just forward of the gearbox, resulting in substantial damage to the tail boom.
Maintenance History
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, anticipating that additional maintenance was still planned for the gearbox. He then installed the tail rotor drive shaft cover. The mechanic moved on to another project and did not make a logbook entry of the work completed or that the bolts were only hand-tightened.
Another mechanic later performed additional maintenance to the gearbox, but the bolts were not checked because the maintenance manual did not require the removal of the tail rotor drive shaft cover. A 0.2-hour maintenance flight check was conducted, and the helicopter was returned to service. The incident occurred upon the first engine start after it had been returned to service.