Incident Description
According to the official investigation, the flight conditions for the air ambulance trip consisted of a clear, moonless, dark night. The destination airport was in a mountain valley, with the only ground reference lights being those of the town adjacent to the airport. The aircraft was seen by witnesses to overfly the town and the airport at pattern altitude, then head out over a lake north of the airport.
Witness Accounts
Approximately 1 mile from the runway, witnesses observed the aircraft suddenly pitch up, roll inverted, and dive straight down into the lake, identified as Bridgeport Reservoir. The aircraft was heading away from the only ground reference lights and was over a reflective body of water near the base turn point when the accident occurred. Witnesses also reported hearing increased engine or propeller noise before impact.
Wreckage and Occupants
Examination of the wreckage revealed evidence of power at impact. Both occupants, a pilot and a nurse, were killed.
Pilot Duty Schedule
The shifts for the pilots in the operation consisted of 4 days on, 2 days off, with alternating day and night shifts. The accident pilot was on the 4th night of the current shift cycle and was also giving flight instruction during the days.
Probable Cause
The official findings list two occurrences. Occurrence #1: loss of control in flight during the approach phase, specifically on the base leg or base to final. Findings include: light condition (dark night), inadequate visual lookout by the pilot in command, inadvertent use of flight controls, failure to maintain proper altitude, impaired visual or aural perception, spatial disorientation, fatigue due to circadian rhythm, fatigue due to flight and ground schedule, and insufficient standards or requirements by the company or operator management. Occurrence #2: in-flight collision with terrain or water during an uncontrolled descent, with the finding that the descent was uncontrolled by the pilot in command.