NTSB Identification: WPR10LA298
14 CFR Part 91: General Aviation
Accident occurred Friday, June 18, 2010 in Hillsboro, OR
Probable Cause Approval Date: 04/07/2011
Aircraft: ROBINSON HELICOPTER R22 BETA, registration: N2548S
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.

As the pilot was approaching the destination airport after a local flight, the helicopter's engine rpm began to fluctuate between 100 percent and 60 percent. Although lowering the collective and manipulating the throttle temporarily increased the rpm, it began to fluctuate again, with the rpm decreasing. After the low rotor rpm warning horn and light activated, the pilot made the decision to perform an autorotation to a nearby open field. The helicopter touched down on the skids and subsequently rolled over onto its side. Prior to the accident, the helicopter's engine had been reportedly experiencing rpm fluctuations. A postaccident examination was performed on the engine and the magnetos and governor underwent further analysis. No evidence was found of an anomaly or malfunction that would have prevented the engine from producing normal power.

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

A partial loss of engine power while on approach for undetermined reasons.

Full narrative available

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