What happened
The accident occurred during a night arrival at an airport in Quincy, Illinois. The pilot had been cleared for an Instrument Landing System (ILS) approach to Runway 4. At the time of clearance, weather conditions were marginal, with a measured ceiling of 200 feet overcast and visibility of one-half mile in fog. Wind was from 080 degrees at 17 knots. The minimums for the approach required a 200-foot ceiling and one-half mile visibility.
The pilot was cleared to begin the descent from a seven-mile Distance Measuring Equipment (DME) arc. As the aircraft descended on the final approach path, radar contact with air traffic control was lost. The pilot was instructed to switch to Quincy Radio for further instructions. When the pilot reported passing the Quincy VOR, which was located just short of the ILS outer marker and the final approach fix, a Flight Service Station specialist advised him that visibility had deteriorated further to three-eighths of a mile.
After reporting passage of the outer marker, radio contact was lost, with only the sound of a keyed microphone audible. The aircraft subsequently impacted trees well to the left of the ILS centerline, approximately three-tenths of a mile west from the approach end of Runway 4.
The investigation
Examination of the wreckage and review of operational data revealed no pre-accident malfunction or failure of the aircraft systems. Additionally, there was no evidence of malfunction or failure in the ILS facility that would have contributed to the accident.