Accident Overview
An emergency medical services (EMS) airplane operating under Part 135 as a commercial air ambulance departed eastward from a high-altitude airport (elevation 6,814 ft msl) in dark night visual conditions. The flight was intended to transport a 15-month-old patient between hospitals. Witnesses observed the airplane turn left to the north and disappear shortly after takeoff.
Accident Sequence
Satellite tracking data showed the airplane at 6,811 ft msl, a ground speed of 115 knots, and a heading of 072 degrees. The airplane subsequently impacted terrain at an elevation of 6,860 ft msl about 4 miles southeast of the departure airport. The debris path indicated a heading away from the destination airport. Initial impact occurred with trees at 6,860 ft, and wreckage was scattered over 1,100 ft down a 4.5-degree slope on a magnetic heading of 141 degrees. The computed descent angle was 13 degrees, with an impact angle of 8.5 degrees. A post-impact flash fire was evident.
Investigation Findings
All six occupants—pilot, flight nurse, paramedic, patient, and the patient's mother—sustained fatal injuries. The aircraft was not equipped with a flight data recorder or cockpit voice recorder, and none were required by federal regulations. Examination of the engines and propellers revealed signatures consistent with power in a mid to high range. The flaps and landing gear were retracted, indicating no attempt to land. Flight control continuity was established, with control cable and push rod breaks showing overload signatures. No pre-impact mechanical malfunction was found.
The pilot had 2,775 total flight hours, with 23 hours in the accident airplane. Toxicology testing detected chlorpheniramine (an over-the-counter antihistamine known to cause impairment at typical doses) and acetaminophen (a pain reliever often combined with chlorpheniramine). Because no blood was available, the time of last use and extent of impairment during the flight could not be determined.
The impact damage, dark night conditions, pilot experience level, and anomalous flight path are consistent with spatial disorientation.
Probable Cause
The National Transportation Safety Board determined the probable cause of this accident was failure to maintain clearance from terrain due to spatial disorientation.