BELL 407Rogers Helicopters

The commercial pilot of the helicopter air ambulance flight, which was operating under visual flight rules, departed in night visual meteorological conditions (VMC) to transport a patient from Porterville, California, to a hospital in Bakersfield, California; a flight nurse and a paramedic were also aboard the helicopter. GPS data indicated that, after takeoff, the helicopter proceeded on a southerly course paralleling a highway and ascended to a maximum GPS altitude of 1,554 ft with groundspeeds varying between 124 and 144 mph. About 13 minutes after takeoff, the helicopter began to descend; 20 seconds later, the helicopter entered a left descending turn with groundspeeds that initially increased and then decreased. According to the last 6 seconds of GPS data, the descent rate of the helicopter was about 2,210 ft per minute. Although both the departure airport and an airport near the helicopter's intended destination reported VMC shortly after the accident flight began, no recorded weather observation stations were located along the route of flight. Meteorologists at the National Weather Service field office nearest to the accident site indicated that the conditions at the time and the location of the accident were conducive to fog. They also referenced a Twitter post from an individual that observed fog in the area of McFarland, however the Twitter post was unavailable. The pilot of the helicopter that located the wreckage about 1 hour, 51 minutes after the accident reported ground fog in the area. In addition, that pilot stated that he encountered heavy rainfall in the general search area. Thus, it is likely that the accident pilot encountered an area of reduced visibility due to rain or fog. Examination of the accident site indicated that the helicopter impacted open, sparsely populated, unlit, and hilly terrain in a descending left turn. Postaccident examination of the helicopter structure, systems, and engine revealed no evidence of any anomalies that would have precluded normal operation. The operator used two Bell 407 helicopters for helicopter air ambulance operations; one was equipped with an advanced (glass cockpit) instrument display system (the accident helicopter), and one was equipped with analog instruments. A review of the pilot's logbook and company records revealed that the pilot had primarily flown the Bell 407 helicopter that was equipped with analog instruments. The pilot's commercial pilot certificate included an instrument helicopter rating, so he most likely had the operational skills necessary to safely conduct a flight in a familiar helicopter. However, during the almost 7 months preceding the accident, the pilot had 11.2 hours of total flight experience in the accident helicopter that included 2.3 hours of night flight time, of which 2 hours comprised of night flight training and night vision goggles (NVG) training about 4 months before the accident. The pilot had logged .3 hours of night time in the accident helicopter 48 hours prior to the accident.  Thus, the pilot lacked recent nighttime experience with the accident helicopter's advanced avionics, which may have increased his susceptibility to spatial disorientation or loss of control during maneuvering flight.