What happened
The flight was initially destined for Sioux Falls. As the aircraft approached that airport, the pilot received weather reports indicating conditions were below minimums. Consequently, the pilot initiated a diversion. While passing over Sioux Falls, the pilot observed that Mitchell, South Dakota, appeared to have clear weather and elected to land there instead.
The weather conditions remained visually acceptable until the aircraft was established on short final approach for landing at Mitchell. At this point, with the landing light illuminated, the pilot lost visual references to the runway environment. The pilot turned off the landing light, which allowed the runway lights to become visible again at approximately 20 feet above ground level.
As the aircraft continued its descent, the runway lights became barely visible. The pilot flared the aircraft at an angle toward the runway edge. Realizing the aircraft was headed for the side of the runway, it was too late to correct the trajectory or execute a go-around. The aircraft touched down with approximately half of the main gear on the runway and half off.
After traveling about 20 feet through snow that was approximately six inches deep, the nose gear failed.
The investigation
The investigation focused on the mechanical failure of the landing gear following the excursion. The primary finding was the structural failure of the nose gear after it impacted the ground and snow outside the paved runway surface.
Findings
Contributing factors included the loss of visual references during the final approach due to weather conditions and lighting configuration. The pilot's decision to land in deteriorating or obscured visibility led to a misaligned touchdown. The subsequent impact with the snow-covered ground off the runway edge caused the mechanical failure of the nose gear.
Safety message
Pilots should be aware that turning off landing lights during final approach can significantly reduce situational awareness if visual references are already marginal. Maintaining positive visual contact with the runway environment is critical for a safe landing, especially when weather conditions are below minimums or visibility is poor.