What happened
On September 18, 2020, a Cessna 152, registration PR-FFE, was conducting a flight training mission departing from Bacacheri Aerodrome (SBBI) in Curitiba, Brazil. The aircraft was occupied by a flight instructor and a student pilot. During the climb to approximately 4,500 feet, the engine experienced a significant power loss, with RPM dropping from normal levels to approximately 1,600 RPM.
In response to the power loss, the instructor took control and declared an emergency. The crew identified an open field in Colombo, Paraná, for an emergency landing. To facilitate the approach, the crew deployed flaps to 30 degrees and opened the aircraft doors. The landing site was an uphill terrain with trees in the approach path, prompting the instructor to execute a sideslip to manage the descent rate. While the initial touchdown occurred, the aircraft bounced and subsequently caps/flipped (capotou) upon a second impact. The aircraft sustained substantial damage, but both occupants emerged uninjured.
The investigation
The investigation conducted by CENIPA focused on the mechanical failure of the Lycoming O-235-L2C engine and the maintenance practices of the flight school. Technical analysis of the engine by the Institute of Aeronautics and Space (IAE) revealed that the engine had been operating at high temperatures, evidenced by light-colored deposits in the combustion chambers of cylinders 1 and 2, indicating pre-ignition and detonation. Furthermore, the engine was found to be operating with a lean air-fuel mixture.
Investigators also examined the maintenance records of the operator. It was discovered that a 100-hour inspection had been performed at a hangar in Curitiba that was not certified for such maintenance activities, and the maintenance organization lacked the required authorization to perform services away from its primary base. Additionally, the investigation noted organizational flaws, including communication gaps between instructors and maintenance staff, and inadequate supervision of maintenance activities.
Findings
- The primary cause of the power loss was the fatigue failure of the intake valve in cylinder 3, which resulted in the valve becoming loose.
- The engine was operating under high thermal stress, likely due to a lean fuel mixture or improper ignition timing.
- Maintenance of the aircraft was performed at an unauthorized location without specific regulatory permission.
- Organizational culture and management supervision contributed to the incident, specifically regarding the lack of oversight in maintenance and communication failures within the flight school.