On July 29, 1998, at 2248 hours Pacific daylight time, a Bell 222B Helicopter, N911RA, was destroyed when it landed hard and rolled over while landing at a makeshift landing spot near Tranquility, California (approximately 25 statute miles southwest of Fresno). The helicopter was owned and operated by Rogers Helicopters of Clovis, California, and was on a positioning flight under 14 CFR Part 91 for an aeromedical evacuation mission when the accident occurred. The commercial pilot and two flight nurses were not injured. Some minor damage to farm equipment at the landing zone was incurred. Night visual meteorological conditions prevailed and a company VFR flight plan was filed. According to statements from the pilot and the flight medical personnel onboard, the purpose of the flight was to air-evac two victims of an automobile crash on a local highway. Responding ground units to the traffic accident from the Fresno County Sheriff and the California Department of Forestry fire department set up a landing zone in a farmyard. The pilot and ground witnesses described the landing zone as a confined dirt lot roughly 150 feet square surrounded by silos, power lines, trees, and buildings. Emergency vehicles were using their headlights to illuminate the landing area and a fire person was functioning as a ground guide for the landing. The pilot stated that he made three high recon orbits around the landing site prior to making the landing approach. The pilot and the medical personnel onboard said that as the helicopter neared touchdown it was "engulfed in a large cloud of dust very quickly" to the point where visual contact with the ground was lost. The pilot tried to focus on the ground through the chin bubble window and added collective in an attempt to climb out of the dust; however, the right wheel touched down and the helicopter rolled over. The flight nurse seated in the rear cabin reported that the helicopter touched down once, climbed up, and then began a drift to the right before contacting the ground again and rolling over. A deputy sheriff 60 feet from the landing spot said that as the helicopter descended from 15 to 3 feet above the ground a dust cloud began to form, which thickened until the only thing he could see of the aircraft was the landing lights and the front wheel. The helicopter suddenly dropped to the ground and bounced on its wheels and then the deputy heard the engine noise increase in pitch and sound. It rose about 3 feet off the ground, drifted to the right about 6 feet, and then rolled over. A Safety Board computer program was used to compute the location and illumination percentage of the moon at the time, coordinates, and altitude of the accident. For the longitude, latitude, and elevation of the accident site, the end of astronomical twilight occurred at 2153 hours. At the time of the accident, the moon was 10.9 degrees above the horizon on a magnetic bearing of 239.5 degrees, with 38 percent of the disk illuminated.