Robinson Helicopter R22 BETA N2548S accident near Hillsboro, Oregon

Probable cause

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

NTSB analysis

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.

Text from the NTSB. Open the NTSB docket for WPR10LA298 for the full record.