Accident Details
On June 18, 2010, at approximately 2045 Pacific daylight time, a Robinson R-22 Beta helicopter, registration N2548S, impacted terrain during an autorotational landing about half a mile south of Portland-Hillsboro Airport in Hillsboro, Oregon. The private pilot and passenger were not injured. The helicopter, owned and operated by Hillsboro Aviation, sustained substantial damage to its rotor system and fuselage.
The flight was conducted under 14 Code of Federal Regulations Part 91 as a personal pleasure flight, operating in visual meteorological conditions. No flight plan was filed. The helicopter had departed Portland-Hillsboro Airport approximately 38 minutes prior to the accident.
Pilot Report
According to the pilot, while executing a visual flight rules (VFR) approach to the airport, approximately one mile from the helicopter landing pad, the engine rpm suddenly began fluctuating between 60 and 100 percent. The pilot lowered the collective and rolled on the throttle, which initially appeared to help. However, the condition resumed with rpm fluctuating to even lower levels, triggering the rotor low rpm warning horn and light.
Realizing he could not reach the landing pad, the pilot elected to perform an autorotational landing to a nearby open field. The helicopter initially touched down on its skids but subsequently rolled onto its side, and the rotating main rotor blades struck the terrain.
Previous Maintenance Issue
The pilot reported that earlier the same day, the helicopter had been written up for fluctuating engine rpm. However, Hillsboro Aviation maintenance personnel were unable to determine the cause of the fluctuation or reproduce the reported problem.
Post-Accident Inspection
An inspection of the engine and rotor control system was directed and monitored by the Federal Aviation Administration (FAA). The magnetos and engine rpm governor were sent for further inspection and analysis. The inspection and testing process did not find any evidence of an anomaly or malfunction that would have prevented the engine and rotor from producing and maintaining 100 percent rpm.