What happened
Simmons Airlines Flight 1746 was conducting an arrival at Phelps Collins Airport when it received weather information from Wurtsmith Air Force Base Approach Control. The initial report indicated that visibility was one-half mile with light drizzle and fog, and the ceiling was at 100 feet overcast. Despite this, the flight continued its instrument landing system approach. However, a special weather observation taken shortly before showed that visibility had dropped to three-eighths of a mile, which was below the required minimums. This critical update did not reach the approach controller in time due to delays in the non-automated weather reporting system.
The pilots were unable to clearly see the runway lights during the first attempt and executed a missed approach. They then elected to try a second instrument landing system approach. By this time, another special observation confirmed that visibility had further decreased to one-quarter of a mile. The station manager at Alpena attempted to contact the flight with this information but was unsuccessful. Approximately 20 minutes after the initial weather report, the aircraft struck trees about one and a half miles short of Runway 1. Evidence indicated that the flight continued below the instrument landing system glide slope and decision height without obtaining visual reference to the runway.
The investigation
The investigation focused on the sequence of events leading to the crash and the condition of the aircraft. Investigators examined the weather data available to air traffic control and the airline station manager. They reviewed the communication logs between Wurtsmith Air Force Base Approach Control and the flight, as well as the attempts by the Alpena station manager to relay updated weather information. The physical evidence at the crash site was analyzed to determine the flight path and impact point relative to the runway.
Findings
The primary factors contributing to this accident were the deteriorating weather conditions and a failure in the communication of critical weather updates. The visibility dropped below minimums, but the information was not relayed to the approach controller or the flight crew in a timely manner due to the slow, non-automated weather reporting system. The pilots continued the second approach below the decision height without visual reference to the runway, leading to controlled flight into terrain.
Safety message
This accident highlights the critical importance of timely and accurate weather information dissemination to both air traffic control and flight crews, especially during low-visibility operations. Delays in reporting significant changes in visibility can have fatal consequences when pilots are operating below decision height.