Accident Narrative
The pilot was engaged in low-level surveillance operations. He extended flaps to 10 degrees, descended to approximately 1,400 feet mean sea level, set engine power at about 18 inches of manifold pressure, trimmed the aircraft, and began a grid search of the area. Upon reaching the end of the search area, he banked the aircraft 180 degrees to a northerly, downwind direction, added power, and initiated another pass.
During the pass, the pilot felt the controls become "mushy" and the airplane began to settle. He added a small amount of power but noticed "no response" to the aircraft controls. He then applied full power and attempted to turn the airplane into the wind. However, directional control continued to deteriorate, and it became evident that he was in a "stall situation." Subsequently, the airplane impacted trees and came to rest inverted on the ground.
Findings
The aircraft was being operated at low altitude with flaps extended and engine power set to 18 inches of manifold pressure during the grid search. The pilot performed a turn to a downwind direction, after which control response degraded, leading to a stall. No specific cause for the loss of control is stated in the source material.