What happened
During the initial climb phase following takeoff, the pilot of the aircraft experienced a gradual loss of airspeed. Although the pilot initially believed the throttles had been inadvertently moved to a lower power setting, engine instrumentation confirmed that takeoff power was being maintained. Recognizing that the aircraft lacked the performance to return to the departure airfield, the pilot identified a suitable area for an emergency descent and maneuvered the plane between two trees.
The pilot, who was the only person on board, sustained serious injuries during the impact.
Findings
Post-accident analysis determined that both propellers were positioned at or near a feather pitch angle at the moment of impact, despite the engines being under power. The investigation focused on recent maintenance performed on both engines immediately preceding the flight. During this maintenance, the ground idle stops had been adjusted, with the left engine configured to follow the settings of the right engine.
The mechanical failure was attributed to a misrigging of the right engine. Because the system relied on a squat switch located on the right landing gear, the extension of the right strut during takeoff caused oil pressure to vent from the domes. This pressure loss allowed the propeller cylinder springs to drive the propellers toward the feathered position.