NTSB Identification: DEN03LA020.
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Accident occurred Monday, December 02, 2002 in Monticello, UT
Probable Cause Approval Date: 03/02/2004
Aircraft: Aerospatiale AS-350BA, registration: N20840
Injuries: 1 Minor.

NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

According to the pilot, he had moved approximately 80 bags of seismic sensor cable earlier that morning with no problems. At approximately 1120, the pilot stopped operations to change lines. He proceeded to pick up five bags and was en route to the drop off point. During the approach to the north, the pilot "noticed that the Nr (rotor rpm) was high at roughly 400 rpm as [he] turned to the west." As the pilot slowed down, he added collective to reduce the rotor speed. The rotor rpm began to slow, at which point the pilot lowered the collective and applied forward cyclic to maintain forward airspeed. The rotor speed continued to decrease and the "low rotor speed warning horn" sounded. The pilot lowered the collective and flared, at which point the bags contacted the ground. The pilot then "noticed that the Nr was low" at approximately 320 rpm. The pilot "zeroed the airspeed, pumped the collective once[,] trying to slow the rate of decent and pulled up on the collective," just before impacting the ground. The helicopter settled onto the load beneath it, and subsequently rolled over on its right side causing substantial damage. An examination of the helicopter revealed no anomalies.

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

the pilot's failure to maintain rotor rpm. A related factor was the presence of an object in the path during the touchdown.

Full narrative available

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