Approach and Instructions
The pilot contacted Des Moines approach control for landing instructions. Approach control directed the pilot to fly inbound on the extended centerline for runway 23 before turning onto a left downwind for runway 31L. Air traffic control tower (ATCT) then instructed the pilot to turn left on downwind for runway 31L at mid-field.
Request for Alternate Runway
Two minutes later, the pilot contacted the tower and asked if he could land on runway 31R. The tower controller told the pilot to keep the turn tight and inquired if the pilot could turn base from his current position. The pilot replied that he could.
Witness Observations
Witnesses on the ground observed the airplane in a constant bank, starting from downwind until rolling wings level on final approach. The airplane's wings were level only for a moment before the airplane sharply rolled into a 90-degree bank angle and impacted the ground.
Post-Accident Examination
An examination of the airplane revealed no pre-impact anomalies.