What happened
On February 21, 2015, a CAP-4 aircraft, registration PP-HGB, was conducting a flight training mission departing from Bragança Paulista (SBBP), Brazil. The flight was intended to follow a route toward São João da Boa Vista before returning to the origin. On board were an instructor and a student pilot.
Approximately one hour into the flight, the instructor attempted to switch the fuel selector from the lower tank to the "both" position. Immediately following this maneuver, the engine experienced a significant power loss, followed by a drop in RPM. The engine subsequently ceased operation. The crew initiated a glide procedure and attempted an in-flight restart, but the engine failed to relight. The instructor performed an emergency landing in a sugarcane field. During the landing, the aircraft struck the crops and overturned, resulting in substantial damage to the airframe. Both occupants escaped the accident uninjured.
The investigation
CENIPA investigators focused on the fuel system to determine the cause of the power loss. During the inspection, fuel collected from the filter bowl exhibited a different color than standard aviation gasoline, suggesting possible water contamination.
Laboratory analysis conducted by the Institute of Aeronautics and Space (IAE-DCTA) confirmed that while the engine oil and the fuel in the lower tank met established standards, the sample taken from the filter bowl consisted almost entirely of water. The investigation revealed that the refueling equipment at the Bragan_ça Paulista aerodrome had undergone maintenance, including system cleaning and pump maintenance, on February 20, 2015—just one day prior to the accident. It was determined that this maintenance work likely introduced water into the stored fuel.
Findings
- Water contamination in the fuel filter bowl caused the engine failure during the fuel selector change.
- Maintenance performed on the aerodrome's refueling system the previous day likely introduced the contaminant.
- Airport infrastructure was a contributing factor.