What happened
On December 8, 2006, a Cessna 182H (registration D-EFVU) departed from Santarém Aerodrome for a 15-minute training flight intended to familiarize a pilot with the aircraft type. The flight was accompanied by an instructor. Shortly after takeoff, at an altitude of approximately 50 feet, the engine began to malfunction.
The instructor immediately took control of the aircraft and initiated a gentle right turn, attempting to reach a nearby cornfield for an emergency landing. During this maneuver, the instructor repeatedly operated the fuel injection pump to maintain power, but the engine continued to run erratically before eventually failing completely.
Unable to reach the intended landing site, the aircraft lost altitude and struck the right bank of the Tagus River at an elevation of approximately five meters. The aircraft impacted a dense cluster of willow trees, which cushioned the impact and prevented the plane from sliding into the river, though the tail section became submerged in the water. Both occupants escaped the wreckage uninjured.
The investigation
The GPIAAF investigation focused on the engine failure and the condition of the fuel system. While the aircraft had undergone a 100-hour annual inspection and a successful ground run a week prior, the investigation revealed that the aircraft had been parked for 42 days during a period of heavy rainfall.
During the pre-flight inspection on the day of the accident, the pilot noted that significant amounts of water were drained during the fuel sump checks. As a precaution, the engine was run for 10 minutes without any apparent issues, leading the crew to deem the aircraft airworthy for the flight. However, post-accident analysis of the wreckage uncovered that the left wing fuel tank cap was damaged, allowing rainwater to enter the tank. Further inspection of the carburetor bowl revealed the presence of water, and the entire fuel system was found to be contaminated with water.