Summary
A commercial pilot was operating an airplane on a local flight when the airplane rolled inverted, descended, and struck a river in a nose-down attitude. The pilot reported feeling a shudder and recalling being inverted, but could not recall further events. The pilot thought the airplane may have stalled.
Flight History
Before the accident flight, another pilot had flown the same airplane on a local flight and reported no mechanical issues with the airframe or engine. Subsequently, a certificated commercial pilot boarded the airplane for a flight. The first pilot observed the airplane take off to the north, level off, and then lost sight of it.
Witness Observations
Witnesses reported seeing the airplane bank left and right, followed by the airplane rolling upside down. Once inverted, the airplane began a gradual descent, which then transitioned into a near vertical descent. The airplane impacted a river in a nose-down attitude.
Pilot Statement
The second pilot stated that he banked left to depart the traffic pattern. He thought he observed another airplane in close proximity and banked back to the right. The pilot felt the airplane shudder and recalled being inverted, but could not recall anything after that point. The pilot further stated that he thought the airplane had stalled.