What happened
The pilot was conducting an instrument approach to the airport at Rochester using a coupler autopilot system. Shortly after passing the middle marker, the aircraft encountered turbulence. During this time, substantial deflections were observed on both the OBS (Omni-Bearing Selector) and GS (Glideslope) indicators.
Despite these indications, the aircraft collided with the terrain approximately 4,000 feet from the runway. A crosswind of 17 knots, oriented 50 degrees to the runway heading, was present during the approach phase.
The investigation
The investigation focused on the flight path and environmental conditions at the time of the accident. The primary mechanical observation involved the significant deflections noted on the navigation instruments during the encounter with turbulence.
Findings
The presence of a crosswind component perpendicular to the runway heading contributed to the difficulty in maintaining the correct approach path. The turbulence encountered shortly after the middle marker likely caused the substantial instrument deflections and loss of control or situational awareness leading to the collision.