Accident Overview
On the day of the accident, N69BS, a general aviation aircraft, was conducting an approach to a non-towered airport. Witnesses observed the flight enter a downwind leg for runway 30 after completing a published approach to runway 12, with a circle-to-land maneuver. The aircraft had been seen below the clouds, which had jagged ceilings estimated at 400 to 500 feet above ground level by a commercial pilot among the witnesses.
Witness Observations
As the aircraft proceeded downwind, it momentarily entered a cloud. Upon exiting the cloud, the airplane turned left, initially with an estimated 30-degree bank. The bank angle rapidly increased to an estimated 70 to 80 degrees. Witnesses saw the tail rise and the aircraft impact the ground nose-first. Several pilots at the airport heard a radio transmission from N69BS on the UNICOM frequency. The transmission included the pilot stating that he had broken out at 2,200 feet, followed by "N69BS turning base," and then exclamations of "lookout" and "oh ...." All eye witnesses agreed that the engine sound remained constant and no engine problems were observed or heard throughout the sequence.
Approach and Flight Path
The published approach in use was the GPS (Global Positioning System) Runway 12 approach. The pilot made an initial approach to Runway 12, then broke off to the right and entered a right downwind for a landing on Runway 30. Published circling minimums for the approach specified a minimum descent altitude (MDA) of 4,800 feet, with a height above terrain (HAT) of 869 feet. Visibility requirements were 1 mile for an approach speed of 90 knots and 1 1/4 miles for 120 knots. The field elevation was 3,931 feet. The approach profile for the GPS Runway 12 approach describes a course from the Jesee waypoint (IAF) at 7,000 feet on a 204-degree heading to the Dezzi waypoint. From Dezzi, the course changes to 114 degrees with a descent to 5,600 feet to the Sophi waypoint. After Sophi, descent to 4,800 feet continues to the missed approach point at the Ruste waypoint. The distance from Dezzi to Ruste is 10 miles.
Probable Cause
The official probable cause of the accident was the pilot's failure to maintain control of the airplane while turning to base leg. Contributing factors were low ceilings, clouds, and the pilot's failure to adhere to both the published approach procedures and the published minimum descent altitude.