What happened
During the early morning hours, an aircraft was performing an arrival procedure approximately 22 miles from the destination airport. While positioned at 8,500 feet, the pilot requested an ILS runway 26 approach. At the time of the request, the automated weather information indicated visibility of only 1/8 mile due to dense fog, which was significantly below the required 3/4 mile minimum for the approach.
Air traffic control provided vectors that resulted in the aircraft intercepting the localizer at the outer marker at an angle of 35 degrees, exceeding the maximum permitted intercept angle of 30 degrees. This maneuver placed the intercept point approximately 3 miles closer to the airport than the required distance. Additionally, the aircraft was positioned 650 feet above the established glideslope at the outer marker.
Rather than initiating a missed approach, the pilot proceeded with the ILS. While attempting to descend and intercept the glideslope from a higher altitude, the aircraft entered a high rate of descent and descended through the glideslope. During efforts to arrest this descent, the aircraft struck level terrain roughly 1,000 feet before reaching the runway. There were no survivors reported in the crash.
Findings
Investigation into the sequence of events identified that the pilot's decision to continue the approach despite being outside of established parameters was a critical factor. The aircraft was flying at an improper intercept angle and an altitude that exceeded the glideslope parameters at the outer marker, all while operating in visibility conditions that were below the published minimums.