LAX04FA076 · Agusta A109A

Following an encounter with night instrument meteorological conditions, the emergency medical services (EMS) helicopter collided with rising hilly terrain while attempting to reverse course in a narrow mountain valley near Redwood Valley, California. The purpose of the flight was to pickup a patient at a rural hospital in a mountainous area for transport to a larger medical facility. When weather conditions would not permit reaching the rural hospital, common practice for the operator's flight crews was to fly to an intermediate airport with an instrument approach where the helicopter could meet ground transport of the patient and continue the evacuation. Prior to departure from home base, the pilot received a weather briefing from DUATS, which indicated that areas along the route of flight would experience light rain showers, as well as cloud layers that ranged from 1,500 feet above ground level (agl) to 6,000 feet agl ,and visibilities between 3 to 5 statute miles (sm). The pilot filed an instrument flight rules flight plan from his home base to the intermediate airport. An employee of another EMS operator based at the intermediate airport said that there was rain and reduced visibilities at the airport, and that she told the accident medical crew by radio that they should come inside and wait for the ambulance to get to the airport because of the weather. Once the accident helicopter arrived at the intermediate airport, the helicopter was not shut down, the flight nurses got out and got back in, and helicopter departed the airport. Communications between a fire department dispatcher and the accident medical crew indicated that the accident flight was attempting to fly to the fire department's helipad located between the intermediate airport and the hospital. Recorded company communications indicated that a few minutes after the conversation with the fire department dispatcher, the accident flight was diverting back to the intermediate airport. There were no further communications with the accident crew. Witnesses in the area of the accident site all reported heavy rain and wind and poor visibilities due to a heavy fog in the area. Another witness about 2 miles south of the accident site reported hearing the helicopter flying very low over her house, just above the 100-foot tall treetops, about 12 minutes before the accident. The charge nurse at the rural hospital indicated that the weather was poor, and she had indicated to the operator's dispatch that the rural hospital would transport the patient to the intermediate airport. The accident area was located in a narrow valley with mountain peak elevations ranging up to 2,000 feet on either side of a major highway that ran in a north/south direction. The airframe and engines were inspected with no preimpact mechanical anomalies noted.

Verbatim NTSB analysis and probable cause from the NTSB dataset