What happened
During the initial stages of the flight, the pilot attempted an Instrument Landing System (ILS) approach. While performing this first approach, the aircraft drifted through the localizer course. Although the pilot successfully realigned the aircraft with the final approach path, the plane remained approximately 500 feet above the required altitude at the decision height. Consequently, the pilot initiated a missed approach and was provided with radar vectors to facilitate a second ILS approach.
While flying inbound on this second attempt, an observer noted the aircraft at an altitude of roughly 150 feet above the ground. At that moment, the plane was in a steep 80-degree right bank with a 60-degree nose-low attitude. The aircraft struck the ground approximately 2,150 feet west of the runway threshold and 720 feet north of the extended centerline. Post-impact inspections of the airframe, engines, and propellers showed no evidence of mechanical failure or anomalies prior to the crash.
Findings
Investigation into the flight data revealed that the calibrated airspeed was approximately 130 knots during the final approach. However, in the 20 seconds leading up to the loss of radar contact, the airspeed dropped to between 95 and 100 knots. At the time of the accident, the aircraft's flaps were set to the 5-degree position. Given the aircraft's weight, the wings-level power-off stall speed was approximately 91 knots. The investigation noted that the flight profile for a 5-degree flap landing requires a minimum Vref airspeed of 115 knots, and the observed loss of airspeed brought the aircraft dangerously close to its stall threshold.