This April 2009 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.
Aircraft: Maule M-4-220C. Injuries: 1 Fatal. Location: Hungry Horse, Mont. Aircraft damage: Destroyed.
What reportedly happened: The private pilot’s logbooks revealed that he had a history of flying in marginal weather conditions. He had performed multiple Special VFR takeoffs and landings. The pilot, who did not have an instrument rating, departed for a short local flight in visual meteorological conditions. He proceeded to climb to the northeast, through a mountain pass, and then to the south, paralleling the shore of a frozen, snow-covered reservoir. The flight continued for about 20 miles. Analysis of radar and recorded GPS data showed that the airplane then experienced large fluctuations in ground speed while still on the same approximate track. While performing a 180° left turn, the Maule crashed. GPS data, airplane instrumentation, and ground scars indicated that the airplane was in a descending left turn when it hit the ground.
All major sections of airplane were accounted for at the accident site, and the post-accident examination of the engine and airframe revealed no obvious anomalies that would have precluded normal operation. Mountain obscuration and occasional precipitation were forecast for the area. Additionally, weather observation stations and local pilot reports indicated that moderate snow showers were in the vicinity of the site at the time of the accident. The white surface of the frozen lake, in conjunction with the snow and limited visibility, would have provided the pilot limited external visual references, and could have resulted in him becoming spatially disoriented or affected by a visual illusion.
Probable cause: The pilot’s improper decision to continue flight into an area of reduced visibility and snow showers during cruise flight, which resulted in spatial disorientation and subsequent loss of aircraft control.
For more information: NTSB.gov