What happened
On April 7, 2010, an Aeroboero AB-115, registration PP-GBW, was conducting a touch-and-go training flight at the Porto Nacional Aerodrome (SBPN) in Brazil. The flight was operated by Aeroclube de Porto Nacional with an instructor and a student on board.
During the climb following the second go-around, the crew heard a loud noise from the engine, which was immediately followed by a significant drop in RPM and a loss of engine power. As the aircraft lost altitude rapidly, the instructor took control and attempted an emergency landing on a nearby dirt road. During the final approach and maneuvering to avoid people present in the landing area, the left wing of the aircraft struck a low-voltage utility pole. The impact caused severe damage to the aircraft's wings, propeller, engine, and landing gear, and the left wing partially detached from the fuselage.
The investigation
CENIPA investigators examined the engine and the maintenance history of the aircraft. The investigation revealed that the lower spark plug of cylinder number 04 had become detached from the cylinder, held only by its ignition cable. This was caused by a failed bushing (thread repair) that was not authorized or prescribed by the engine manufacturer's overhaul manual.
Furthermore, the investigation found that the fuel filter was operating without its filtering element. The investigators also noted that the instructor was unable to declare the emergency to the local radio station because the microphone was set to the internal intercom function at the time of the failure. The investigation also highlighted a lack of maintenance traceability and oversight within the flight school's management.
Findings
- Unauthorized engine repair: The primary cause of the engine failure was a non-standard bushing service on the cylinder spark plug, which failed under internal pressure, leading to a loss of compression.
- Inadequate maintenance oversight: The flight school's management failed to properly supervise maintenance activities, allowing unauthorized repairs and the operation of the aircraft with a missing fuel filter element.
- Emergency maneuvering: The collision with the utility pole was a result of the pilot maneuvering to avoid people located on the intended landing strip.
- Personnel: The instructor and student sustained minor injuries.