Incident Summary
Shortly after takeoff, the pilot of a Mitsubishi MU-2 advised air traffic control of a need to return to the airport. When asked about the problem, the pilot requested a moment to stand by. Approximately 30 seconds later, while on a left downwind for runway 35R, the pilot declared an emergency, stating that an engine had been shut down and requesting emergency equipment. The controller and witnesses observed the airplane on the base leg, then overshoot the final approach to runway 35R.
Loss of Control
After the overshoot, the controller cleared the pilot to runway 28, but received no response. The controller then observed the airplane's landing lights turn toward the terrain, and the MU-2 was lost from view. A witness reported seeing the airplane make an immediate sharp left bank and descend, impacting the ground at an angle just less than 45 degrees, nose first.
Flight Path and Performance Analysis
A performance study indicated that while on the downwind leg, the airplane began banking left at a constant angle of about 24 degrees as it turned to base. Twenty-three seconds later, the bank angle increased further during the turn to final, overshooting the runway. At that point, the angle of attack reached a stall angle of approximately 17 degrees. The flight path angle then decreased by 22 to 25 degrees, calibrated airspeed dropped by 40 to 70 knots, and vertical speed indicated a descent rate of 3,000 feet per minute just before impact.
Post-Impact Examination
Examination of the airframe revealed that the flaps were set at 20 degrees and the landing gear was retracted. According to the airplane flight manual, on base leg the flaps should be at 5 degrees with gear extended; when landing is assured, flaps should be extended to 20 degrees while maintaining 125 knots calibrated airspeed (KCAS) on final and 110 KCAS over the runway. The airplane's minimum controllable airspeed (Vmc) is 99 KCAS.
Engine and Propeller Examination
At impact, the left propeller was found feathered and the right propeller in the normal operating range. Examination of the left engine revealed static witness marks on several internal components, with no anomalies that would have precluded normal operation. The reason for the precautionary shutdown of the left engine was not determined. Examination of the right engine showed rotational scoring and metal spray deposits on several internal components. Four vanes of the oil pump transfer tube were separated and missing. The gearbox oil-scavenge pump was not free to rotate and was disassembled, revealing one separated oil pump transfer tube vane inside. Pitting and wear damage were noted on all roller bearing elements and the outer bearing race of the propeller shaft roller bearing. No additional anomalies were found.