What happened
Shortly after takeoff, the pilot of a Mitsubishi MU2 notified air traffic control of the need to return to the airport for landing. While established on a left downwind for runway 3 and 5R, the pilot declared an emergency, stating that an engine had shut down. During the transition from the base leg to final approach, witnesses and air traffic controllers observed the aircraft overshoot the final approach for runway 35R. Following this, the controller cleared the pilot for runway 28, but received no response. An observer noted the aircraft's landing lights turning toward the terrain, followed by a sharp left bank and a nose-first descent into the ground. A performance study indicated that while the aircraft was on downwind, it maintained a constant left bank of approximately 24 degrees. As the aircraft turned to final approach, the bank angle increased, the angle of attack reached a stall angle of about 17 degrees, and the airspeed decreased by 40 to 70 knots. Just before impact, the vertical speed showed a descent rate of 3,000 feet per minute. There were 0 fatalities reported in the provided text.
The investigation
Examination of the airframe showed the landing gear was retracted and the flaps were in the 20-degree position. According to the flight manual, flaps should remain at 5 degrees during the base leg, with extension to 20 degrees occurring only once landing is assured. At the time of impact, the left propeller was feathered while the right propeller was in its normal operating range. Investigation of the left engine showed internal witness marks but no anomalies that would have prevented normal operation; the reason for the pilot's precautionary shutdown of this engine was not determined. However, the right engine exhibited rotational scoring and metal spray deposits on internal components. The oil pump transfer tube was found to have four missing vanes, and the gearbox oil-scavenge pump was unable to rotate. Disassembly of the pump revealed one of the missing vanes inside the unit. Additionally, pitting and wear damage were identified on all roller bearing elements and the outer bearing race of the propeller shaft roller bearing.