NTSB Identification: CHI94LA287.
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Accident occurred Thursday, August 18, 1994 in CUSTER, SD
Probable Cause Approval Date: 01/25/1995
Aircraft: HUGHES 369HS, registration: N74AW
Injuries: 2 Uninjured.

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 PILOT WAS PRACTICING AUTOROTATIONS IN HIS HELICOPTER. DURING HIS SECOND AUTOROTATION THE HELICOPTER'S SKID COLLIDED WITH A ROCK CAUSING THE HELICOPTER TO ENTER GROUND RESONANCE. THE PILOT SAID THE HELICOPTER'S ROTOR BLADES BEGAN '...GYRATING OUT OF THE NORMAL PATH...' STRIKING THE AIRFRAME NUMEROUS TIMES. THE PILOT SAID THE ROCK HIS AIRCRAFT COLLIDED WITH WAS OBSCURED BY GRASS AND THAT HE DID NOT SEE IT. HE SAID HE DID SEE OTHER ROCKS OUT IN FRONT OF HIS AIRCRAFT AS IT DESCENDED.

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

the pilot's selection of unsuitable terrain on which to perform an autorotation. A factor in this accident was the hidden obstruction.

Full narrative available

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