On August 12, 1992, a DE Havilland DHC-2 (registration N8190Y) operated by Alaska West Air Service, Inc. was involved in an aviation accident near Crescent Lake, AK. Investigators recorded the probable cause as: The pilot's misjudgment of altitude during the final approach due to flat lighting and glassy water conditions, which resulted in a premature hard landing and subsequent sinking of the aircraft. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
A pilot lost depth perception due to flat lighting and glassy water conditions, resulting in a premature hard landing that sank the aircraft immediately upon impact with the lake surface.
What happened
The flight was proceeding toward a planned water landing on a large body of water. Approximately five seconds after the pilot leveled the wings during the final approach phase, the aircraft encountered a hard, premature touchdown. The impact caused the floats to separate from the airframe, leading to the immediate sinking of the airplane.
The investigation
Post-accident analysis focused on the circumstances surrounding the loss of depth perception. The pilot reported that flat lighting conditions combined with the reflective nature of the water surface created a "glassy water" scenario. These visual factors caused the pilot to significantly misjudge his altitude relative to the water.
Findings
The primary factor contributing to the accident was the pilot's inability to accurately gauge height above the water due to environmental conditions. The pilot stated that upon impact, he believed the aircraft was still 70 to 80 feet above the surface, indicating a severe disconnect between visual perception and actual position during the final moments of the approach.
Probable cause
The pilot's misjudgment of altitude during the final approach due to flat lighting and glassy water conditions, which resulted in a premature hard landing and subsequent sinking of the aircraft.