Flight and Approach Information
A twin-engine turboprop cargo airplane was conducting a localizer DME back course approach to runway 36 during a night cargo flight under instrument flight rules (IFR). The minimum visibility for the approach was one mile, and the minimum descent altitude (MDA) was 460 feet msl (338 feet agl). Prior to leaving cruise altitude, the first officer listened to the Automatic Terminal Information Service (ATIS) which included an altimeter setting of 29.30 inHg. No other altimeter information was received until the crew reported they were inbound on the approach.
Communication and Altimeter Setting
At that time, tower personnel told the crew that the visibility was one mile in light snow, the wind was from 040 degrees at 22 knots, and the altimeter setting was 29.22 inHg. The crew did not reset the airplane altimeters from 29.30 to 29.22.
Descent and Final Moments
At the final approach fix, 5 miles from the runway, the captain began a descent to the MDA. Thirty-six seconds before impact, the first officer cautioned the captain about the airplane's high airspeed. Due to strong crosswinds, the captain disconnected the autopilot 22 seconds before impact. He said he pushed the altitude hold feature on the flight director at the MDA. Eighteen seconds before impact, the airplane leveled off at about 471 feet indicated altitude, but then descended again 9 seconds later. The descent continued until the airplane collided with the ground, 3.5 miles from the runway.
Crew Observations and Equipment
Both crew members reported that neither the airport nor the snow-covered terrain was observed before impact. The crew reported that the landing lights were off. The airplane was not equipped with a ground proximity warning system (GPWS).