Piper PA 23-250 N54857 accident near Elko, Nevada

Probable cause

The pilot's inadequate preflight weather planning, which resulted in the flight over mountainous terrain into forecast instrument meteorological conditions, icing, and mountain wave, and resulted in an uncontrolled descent and collision with terrain.

NTSB analysis

The commercial pilot departed on the cross-country flight in night visual meteorological conditions over mountainous terrain. About 3 hours after takeoff, the pilot reported to an air traffic controller that he was encountering clouds and was going to turn around to avoid icing conditions. The controller provided the pilot with information for the nearest airport, which was about 40 miles north. The pilot replied that it was "getting super turbulent" and that he was going to "head over" to the airport. Communication and radar contact with the airplane were lost shortly thereafter. Examination of the wreckage revealed no evidence of any preimpact mechanical malfunctions or failures that would have precluded normal operation.

Radar and GPS data revealed that the airplane was flying east when it crossed less than 900 ft above the ridgeline of a high mountain peak and turned toward the downwind (or leeward) side of the ridge, where the airplane began to descend and its speed decayed. The accident site was found near the end of the radar track on the east side and near the summit of the peak, at an elevation about 10,090 ft mean sea level. Review of weather information indicated that the accident site was located in an area favorable for mountain wave conditions with downdrafts as strong as 1,200 ft per minute, and that icing conditions were likely present at the accident site at the time of the accident. It is likely that the downdrafts exceeded the airplane's climb capability and resulted in its descent into terrain.

Although the pilot filed a visual flight rules flight plan, a search of multiple official weather briefing sources revealed that the pilot did not request an official weather briefing before the accident flight. The area of the accident site at the altitude at which the airplane was flying was included in AIRMET's for moderate icing and moderate turbulence. Additionally, winds aloft forecasts near the accident site indicated favorable wind conditions for the development of mountain wave; however, since the pilot did not obtain a weather briefing before the flight, it is likely that he was unaware of these weather conditions along his route, and the hazards that they posed to the flight.

Text from the NTSB. Open the NTSB docket for WPR18FA073 for the full record.