NTSB Identification: CHI99FA285.
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Accident occurred Tuesday, August 10, 1999 in CUSTER, SD
Probable Cause Approval Date: 01/24/2001
Aircraft: Bell 206B, registration: N67JJ
Injuries: 2 Fatal,2 Serious,1 Minor.

NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.

The helicopter impacted trees and terrain while maneuvering during a sightseeing flight over a national park. The helicopter was in a descending left turn and a high angle of bank with decreasing main rotor rpm. A low rpm warning horn was heard several seconds prior to impact with the trees. An acoustical analysis of a video tape taken by a passenger shows a decrease in the engine gear box and planetary speeds along with a steady state engine speed several seconds prior to the end of the video tape. The end of the video tape recorded the initial impact with the trees. Examination of the engine and airframe revealed no anomalies.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

The pilot's failure to maintain adequate altitude/clearance from the trees. Contributing to the accident was the pilot's inadvertent settling with power.

Full narrative available

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