NTSB Identification: CHI00FA110.
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Accident occurred Saturday, April 08, 2000 in LEMONT, IL
Probable Cause Approval Date: 09/26/2001
Aircraft: Hughes 369D, registration: N5070J
Injuries: 1 Minor,1 Uninjured.

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 muddy terrain following an auto rotation while conducting power line maintenance. The autorotation was executed from a hover altitude of 100 feet agl. Review of the helicopter's height velocity diagram indicated that the operation was conducted within the "cross hatched" area. Operation within the "cross hatched" area may not allow enough time for the critical transition from powered flight to autorotation. Examination of the airframe, engine and related components revealed no anomalies.

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

the loss of engine power for undetermined reasons. A factor was the operation within the cross "hatched area" of the helicopter's height/velocity curve by the company.

Full narrative available

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