HISTORY OF FLIGHT On September 22, 2001, at 2006 Pacific daylight time, an Aerospatiale AS350BA helicopter, N911NT, collided with trees after an aborted landing, and came to rest on its side at a ballpark in Butte Meadows, Chico, California. The helicopter, owned and operated by the Enloe Medical Center, was destroyed in the impact sequence. The commercial pilot was fatally injured; one flight nurse sustained serious injuries; and the other flight nurse was not injured. Visual meteorological conditions prevailed for the flight that had departed the Enloe Medical Center at 1947 as a positioning flight under the provisions of 14 CFR Part 91 to pickup a traffic accident victim for transport to the hospital. A company visual flight rules (VFR) flight plan had been filed. The flight was scheduled to terminate at the hospital. According to dispatch records from the hospital, a call came into the hospital at 19:42:29, concerning an automobile accident. At 19:43:15, the flight crew went on standby page, and at 19:43:23, the flight crew received a "go" page. The flight departed from the hospital at 19:47:59, and arrived on scene at the ballpark at 20:05:04. Ground witnesses, who were assisting with landing, stated that the helicopter's approach appeared normal. About 30 feet above ground level (agl), their vision became obscured due to dust and dirt kicked up by the main rotor blades of the helicopter. Witnesses reported that because of the dirt and dust they did not see the impact sequence. However, they heard the engine power up, and depart towards the east, and then heard the impact. The witnesses stated that prior to the dirt/dust storm they did not see or hear any deficiencies with the helicopter. During the engine power up and go-around, the witnesses did not hear any problems with the engine. The National Transportation Safety Board investigator interviewed one of the flight nurses. The flight nurse stated that he was sitting behind the pilot using a pair of handheld Night Vision Goggles (NVG) to assist in making sure that the landing area was clear. He indicated that the approach was normal and there were no discrepancies with the helicopter or engine that he could identify. About 10-12 feet above ground level (agl), during the flare for landing, their vision became obscured by a dirt/dust storm (brown out) initiated by the main rotor blades. The flight nurse stated that he kept asking the pilot if he could see anything, but did not receive a response. He heard the engine power up, with no problem, and then remembers hitting trees. In the operator's statement (NTSB Form 6120.1/2; Pilot/Operator Aircraft Accident Report), the crew made an unsuccessful attempt to contact the incident commander on the ground. The pilot circled the intended landing site two times and then setup for an approach from west to east. The landing zone was in a confined area, and a steep angle approach was made. In the written report, the incident commander indicated that he lost sight of the accident helicopter about 25-30 feet above the ground due to dust kicked up by the main rotor blades. The flight nurses reported that the helicopter became engulfed in the dust and they estimated that the pilot started to pull pitch "somewhere around 12-15 feet above the ground." The operator stated that the intent was to do a "vertical go around." The flight nurses stated that the helicopter drifted 85-90 feet south of the intended landing site. One flight nurse stated that she saw a tree coming into the window prior to the impact. According to the operator, the helicopter came to rest on the front right side, upside down. The landing area was mountainous with large ponderosa pines and cedar trees. The elevation at the landing zone was 4,200 feet mean sea level. The landing zone area was 300 x 100 yards in size, and the operator had been utilizing the landing zone since 1985, with a total of 76 landings at the site. PERSONNEL INFORMATION A review of Federal Aviation Administration (FAA) airman records revealed the pilot held a commercial pilot certificate with ratings for airplane single engine land and multiengine land, rotorcraft-helicopter, and instrument airplane and helicopter. He also held a mechanic certificate with ratings for airframe and power plant. The pilot held a second-class medical certificate issued on November 16, 2000. It had the limitations that the pilot shall possess glasses that correct for near and intermediate vision. According to the Pilot/Operator Aircraft Accident Report, the operator reported the pilot's flight time as 17,163 hours total time, with 1,398 total hours in make and model helicopter. The operator indicated that the pilot had logged 87.6 hours in the last 90 days, and 26.9 hours in the last 30 days, and 1.7 hours in the last 24-hour period. According to American Eurocopter, the pilot had completed factory training on September 11, 2001, at their facilities in Grand Prairie, Texas. Training was conducted in an Aerospatiale AS350 helicopter. According to the operator's training records, the pilot completed Night Vision Goggle (NVG) training on June 15, 2001. AIRCRAFT INFORMATION The helicopter was an Aerospatiale AS350BA, serial number 1556. A review of the helicopter's logbooks revealed a total airframe time of 7,786.9 hours on September 21, 2001, the day before the accident. On June 8, 2001, an annual/500-hour inspection was conducted; the airframe total time was reported as 7,438.1 hours. The last 100-hour inspection was conducted on September 5, 2001, at an airframe total time of 7,742.3 hours. The helicopter was equipped with a Turbomeca Arriel 1B engine, serial number 4836. Total time on the engine on September 21, 2001, was 4,762.1 hours; at the annual inspection the engine total time was 4,413.9 hours. Examination of the helicopter's logbooks revealed no unresolved maintenance discrepancies against the helicopter prior to departure. MEDICAL AND PATHOLOGICAL INFORMATION According to the Butte County Coroner's office, the pilot was pronounced deceased at 2143 at the Enloe Medical Center by the trauma surgeon due to full cardio arrest and massive trauma. An autopsy and toxicological analysis were not conducted. The FAA Civil Aeromedical Institute, Oklahoma City, Oklahoma, did not conduct a toxicological analysis due to a lack of specimens. ADDITIONAL INFORMATION According to the Operations Specifications approved by the FAA for Enloe Medical Center, the flight nurses are considered to be crewmembers and wear night vision goggles. An approved training program is in place.