What happened
On November 1, 2022, a Cessna TU206G, registration HK3072, was operating a non-scheduled passenger flight from El Refugio Aerodrome in La Macarena, Colombia. After departing from runway 35, the aircraft experienced significant fluctuations in engine RPM during the initial climb. The pilot attempted several troubleshooting steps, including switching fuel tanks and using the fuel pump, but the engine instability persisted.
To avoid a more dangerous situation, the pilot executed a controlled forced landing in an unprepared field ahead of the aircraft. During the deceleration phase, the aircraft encountered irregular terrain, which caused the nose gear to fracture and the aircraft to overturn. All four occupants (the pilot and three passengers) were able to evacuate the aircraft on their own and escaped without injuries.
The investigation
The GRIAA investigation focused on the mechanical failure of the engine components and the maintenance history of the propeller governor. Investigators examined the propeller governor, which had been installed on the engine on August 30, 2022. Post-incident testing revealed that the component was improperly calibrated; it failed to reach the required oil pressure of 290 psi, peaking at only 200 psi, and could not achieve the required 2,850 RPM, reaching only 2,600 RPM.
Furthermore, the investigation scrutinized the maintenance practices of the operator. It was determined that during the installation of the governor, non-standard maintenance practices were used, specifically an unnecessary adjustment of the regulation screw. The investigation also identified weaknesses in the operator's quality control and maintenance supervision.
Findings
- The forced landing was necessitated by significant engine RPM fluctuations during the initial climb.
- The propeller governor malfunctioned due to an erroneous calibration of the engine revolutions and insufficient oil pressure delivery.
- Maintenance personnel utilized non-standard practices, including an unnecessary adjustment of the component's regulation screw.
- There were deficiencies in the operator's oversight and quality control regarding maintenance services.