On October 26, 2003, approximately 1215 Pacific standard time, a Hughes 269C helicopter, N7452F, registered to and being operated/flown by a commercially rated flight instructor, sustained substantial damage during a nose down event following a low altitude auto-rotation landing at the Stark's Twin Oaks Airpark, Hillsboro (7S3), Oregon. Both the flight instructor and the pilot under instruction were uninjured. Visual meteorological conditions existed and no flight plan had been filed. The flight, which was instructional, was operated under 14CFR91, and originated from the Hillsboro airport (HIO), Hillsboro, Oregon, at 1145 on the morning of the accident. The instructor reported to an inspector assigned to the Hillsboro Federal Aviation Administration's Flight Standards District Office that he was in control of the helicopter, which was moving forward in a hover at a "brisk walk." He initiated a demonstration of an auto-rotation while in the forward hover to a grassy area slightly east of the runway environment and upon touchdown, the helicopter's skids encountered soft terrain and dug in and the helicopter rocked forward up onto the toes of the skids. Immediately thereafter, the main rotor blades contacted the ground and the helicopter came to rest on the forward skid toes and the main rotor mast. The instructor reported that there was no mechanical malfunction with the helicopter at the time of the event and the terrain at the selected site for the auto-rotation was soft.