NTSB Identification: ATL07LA045.
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Accident occurred Saturday, February 24, 2007 in Bethlehem, GA
Probable Cause Approval Date: 03/31/2008
Aircraft: Hiller UH-12A, registration: N8180H
Injuries: 2 Fatal.
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 attempted a downwind departure at or about maximum gross weight in a very tight landing zone with high obstacles, forcing the pilot to use rotor energy to gain altitude which would have slowed rotor RPM below safe operating limits. With a tailwind the engine had insufficient power for the helicopter to reach transitional lift. Once the pilot determined that he could not regain rotor speed, he would have selected an area in the woods to try and descend. Rotor RPM would have continued to decay and the pilot would have initiated an Auto-Rotation. The pilot closed the throttle as noted by the crushed throttle linkage. The tail-rotor descended into the trees as evidenced by impact marks to the leading edge of the tail-rotor blades. The engine was still developing power to the rotor system as observed in the twisting of the tail-rotor drive shaft aft of the tail-rotor universal joint. The helicopter descended through the trees vertically and nosed down when the main rotor blades exited the helicopter. The metal strip on the main rotor blades contacted the tail boom at the rear universal joint of the tail rotor drive shaft. The helicopter impacted the ground. The transmission and rotor system crushed the flight deck. Examination of the helicopter found no preimpact mechanical failure or malfunctions that would have prevented the helicopter from operating properly.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: The pilot's failure to maintain adequate rotor rpm, which resulted in an attempted autorotation and in-flight collision with trees. Contributing to the severity of the accident was the pilot exceeding the helicopters takeoff capability. Full narrative available
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