McCook-Ben Nelson

The airplane had just departed for a cross-country flight when witnesses observed it flying nose-high but descending. The airplane’s nose pitched downward before the airplane rolled sharply left, consistent with an aerodynamic stall, and collided with trees. Examination of the airframe and engine found no preimpact anomalies. Flight data from the airplane’s onboard engine monitoring system showed that several engine parameters advanced normally for the takeoff portion but then gradually reduced during the takeoff roll and continued to decrease as the airplane began to climb away from the runway. The data stopped seconds before the accident. Estimated weight and balance calculations for the accident flight showed that the airplane was being operated about 550 pounds over its maximum gross weight and 0.5 inches outside of its aft center of gravity (cg) limit. The airplane’s throttle quadrant friction lock was found in the full aft position (disengaged) after the accident. The throttle and condition levers appeared full forward and the propeller level was near mid-travel. Pilot-rated friends who had flown with the pilot reported that he would “ease into the power and not go to full torque.” Accordingly, although the recorded gradual reduction in power was consistent with the engine controls moving during takeoff and rotation, which commanded a reduction in engine power, the reason for the airplane’s reduction in power could not be determined. Toxicology results indicated that the pilot had used the sedating medication zolpidem and may have been experiencing some associated impairing effects at the time of the accident. However, the timing and dosage of the pilot’s last zolpidem use, whether he may have been impaired by it, or whether he may have been experiencing impairing effects from an underlying sleep disturbance that was being treated with zolpidem could not be determined. The pilot’s decision to take off with the airplane loaded about 550 lbs over its maximum gross weight, and outside of its aft cg limit, combined with the gradual reduction in engine power, would have significantly degraded the airplane’s controllability. The pilot subsequently exceeded the airplane’s critical angle of attack during the initial climb, resulting in an aerodynamic stall from which he could not recover.

The part 135 on-demand air taxi flight departed Denver, Colorado, with a destination of Columbus, Nebraska. Weather forecasts were for icing conditions along the entire route of flight. While en route, ATC advised the pilot of reported icing ahead. The pilot was cleared to climb to 19,000 feet to get on top of the clouds. The pilot reported 'some alternator problems,' and requested to divert to North Platte, Nebraska. He then elected to divert to McCook, Nebraska, due to the weather at North Platte. ATC lost communication with the pilot during the diversion. Witnesses reported the airplane circled the McCook Airport twice. According to them, the airplane entered a bank of about 45°, then stalled. Subsequently, it traveled about 190 feet through a stand of trees before coming to rest. Witnesses reported the airplane was covered with ice. One-half inch of mixed ice was found on a piece of windshield. Both alternators had one phase in the stator winding shorted.