Incident Overview
The pilot reported that all preflight checks, engine start, run-up, taxi, and takeoff proceeded normally. During the initial climb after takeoff, at an altitude approximately 1,000 to 1,500 feet above ground level, the engine experienced a gradual power reduction. The pilot described the event as a smooth spool down, similar to a loss of torque or the propeller moving to feather. A forced landing was executed in a field, where the aircraft nosed over and came to rest inverted.
Examination Findings
Post-accident examination of the engine and propeller assembly revealed that the propeller-reversing lever was installed on the incorrect side of the reversing lever guide pin. Additionally, the reversing linkage carbon block was missing and had separated from the aircraft. Review of maintenance records indicated that the carbon block had been replaced during a 100-hour inspection conducted approximately 5 flight hours before the accident. The misinstallation—placing the reversing lever on the wrong side of the guide pin—led to improper seating and accelerated wear of the carbon block.
According to the engine manufacturer, any disconnection in the propeller control linkage allows the propeller governor beta control valve to extend, driving the propeller into feather. This mechanism explains the loss of thrust experienced during the climb.
Probable Cause
The official probable cause is the incorrect installation of the propeller reversing lever and carbon block assembly, which resulted in a loss of propeller thrust.