What happened
Following a period of waiting for a thunderstorm and rain to pass, the pilot attempted takeoff from a gravel airstrip. During the initial climb, the aircraft encountered a downdraft that caused it to descend and touch down on a sandbar in a river adjacent to the airstrip.
The aircraft managed to begin climbing again, but was subsequently forced down by a second downdraft. This resulted in a touchdown on another sandbar. After a third attempt to regain altitude, the aircraft was forced into the river, where it nosed over. The pilot noted that while witnesses observed little to no wind and heard a normal-sounding takeoff, the engine sound quickly diminished, as if the throttle had been pulled back.
The investigation
In a written statement provided after the accident, the pilot indicated that there appeared to be a mysterious loss of power during the event.