Accident Overview
On a local flight from Minneapolis-St Paul International Airport, a Northwest Airlines aircraft (registration NC93037) departed at 0946LT for a six-month instrument competency check. The check involved Captain John R. Galt under the supervision of Captain Ray Render, a company check pilot. On board were also CAA air carrier agent William H Solomon on the jump seat and three CAA personnel from the Minneapolis Control Tower—E. Bergstrom, R. Olsen, and B. Erickson—sitting in the main cabin. The aircraft carried 800 gallons of fuel, weighing 32,943 pounds, within its 38,000-pound maximum. Weather was clear with unlimited visibility.
Sequence of Events
After takeoff, the crew conducted two simulated instrument landing system approaches. At 1025LT, they radioed the control tower that this phase was completed, marking the last known contact. The aircraft was first sighted near Center City, Minnesota, 43 miles northwest of Minneapolis, executing a steep left turn at an estimated 4,000–5,000 feet with landing gear down. After the turn, it began a shallow climb, with engines sounding normal. The witness then looked away; upon returning, the aircraft was partially inverted in a steep dive. It lost approximately 2,500 feet before recovering to level flight and continuing northeast.
Shortly afterward, the aircraft made two or three pitching oscillations, losing about 400 feet per oscillation, accompanied by engine surge noises. It continued northeast, then, two miles south of Almelund, made a shallow 270-degree right turn, returning to a northwestern heading. Gradually losing altitude, the right propeller was observed turning slowly. Near Almelund, at 500–600 feet above ground, the aircraft initiated a steep right turn, lost altitude rapidly, and after roughly 90 degrees of turn, the right wing struck the ground. Five of the six occupants were killed at impact; the sixth died days later without regaining consciousness. The aircraft was demolished.
Investigation
The official investigation determined the probable cause: unwanted reversal of the right propeller during flight, preventing crew control. Supporting findings included a malfunctioning fuel feed valve in the right engine, the right propeller found at 7–10 degrees reverse thrust, and evidence from a similar occurrence indicating dangerous flight characteristics with a reversed propeller. Additionally, retracted wing flaps may have contributed to uncontrollability at speeds below 140 miles per hour.