Approach and Initial Events
The airplane was conducting an instrument landing system (ILS) approach under instrument meteorological conditions. The captain initially stated that the aircraft was on the approach with engine power set at flight idle. Approximately 300 feet above ground level and between one-quarter and one-half mile from the runway threshold, the captain reported making visual contact with the runway.
Engine Anomaly and Stall
The captain stated that the left engine then surged, causing the airplane to yaw right and drift left. At this point, the aircraft was in visual conditions, on glideslope, with airspeed decreasing through 106 knots. The captain aligned the airplane with the runway and attempted a go-around, but reported that the throttles were difficult to move. The airplane began to stall, prompting the captain to lower the nose. Subsequently, the airplane struck terrain approximately 500 feet before the runway.
Pilot Statements and Amendments
After being informed that engine power should not be at flight idle during the approach, the captain amended his statement, indicating that the approach power setting was at 1,000 lbs of torque. The co-pilot initially reported the engine anomaly occurred while at flight idle but later amended his statement, stating the anomaly occurred as power was being reduced toward flight idle, not at flight idle.
Examination Findings
Examination of the left engine revealed no pre-impact mechanical malfunctions. Inspection of the airplane's cockpit showed no anomalies with the throttle levers.
Flight Manual Guidance
Review of the flight manual for the make and model of the accident airplane indicated that during a normal landing, 1,100 lbs of torque should be set prior to turning base leg. The manual further stated to reduce the power levers approximately 30 feet above ground level and initiate a gentle flare.
Weather Conditions
The reported weather at the airport approximately five minutes before the accident included visibility of 3/4 mile in mist and an overcast ceiling at 100 feet. About seven minutes after the accident, reported weather included visibility of 1/4 mile in freezing fog and an overcast ceiling at 100 feet.
Procedure Review
Review of the terminal procedure for the respective ILS approach revealed that the decision height was 200 feet above ground level, and the required minimum visibility was 1/2 mile.