North American AT-6D N49961 accident near Oshkosh, Wisconsin

Probable cause

The pilot’s failure to maintain airspeed while maneuvering, which resulted in the exceedance of the airplane’s critical angle of attack and an aerodynamic stall/spin.

NTSB analysis

The pilot and passenger departed on a local flight and climbed to an altitude of about 3,900 ft mean sea level (msl) while turning to overfly a local lake. After leveling off, the airplane made a turn to the right, followed by a turn to the left. Performance calculations based on ADS-B and winds aloft data showed that, during the turns, the airplane decelerated, and the calculated load factor increased. The airplane slowed to a speed consistent with its published accelerated stall speed, then entered a rapid descent. A witness reported seeing the airplane in a flat spin to the right that continued until the airplane impacted the water.

The airplane was destroyed when it impacted the water. Examination of the airplane, engine, and related systems did not reveal any preimpact anomalies that would have precluded normal operation.

Based on the available information, the pilot likely failed to maintain adequate airspeed while maneuvering and exceeded the airplane’s critical angle of attack, which resulted in an inadvertent aerodynamic stall/spin.

Text from the NTSB. Open the NTSB docket for CEN23FA332 for the full record.