What happened
On July 5, 2014, at 14:40 UTC, a Cessna A150M, registration PT-UUU, departed from the Goiânia National Aerodrome (SWNV) bound for Minaçu (SWIQ) for a private flight. The aircraft was carrying a pilot and one passenger.
During the climb to cruise altitude, once the aircraft surpassed 6,400 feet, the pilot identified engine power loss and torque oscillations. After coordinating with air traffic control, the pilot requested a return to the origin aerodrome. As the aircraft descended, the torque oscillations became more frequent. While passing through 4,000 feet, the pilot determined that the intermittent power loss necessitated an immediate emergency landing. The pilot opted to land on the GO-330 highway, between the cities of Petrolina de Goiás and Ouro Verde. Both occupants of the aircraft were uninjured, and the aircraft sustained no damage.
The investigation
CENIPA investigators examined the engine and propulsion components immediately following the landing. Initial inspections and subsequent maintenance ground runs at a certified workshop failed to replicate the torque oscillations or the power loss.
Because the aircraft had not flown for fourteen days prior to the incident, the investigation focused on the fuel system. The aircraft was carrying approximately 100 liters of Avgas. Although the pilot performed a fuel drain at all five sampling points (wing tanks, collector tanks, and fuel filter) and laboratory analysis of the samples by the National Agency of Petroleum (ANP) showed the fuel met all quality standards, investigators considered the possibility of water contamination.
Technical literature, including FAA Airworthiness Directives and Cessna Service Information Letters, highlights the risk of water entering the fuel tanks of Cessna 100/200/300 series aircraft during exposure to rain or washing. These documents mandate a specific, rigorous draining procedure—including tilting the aircraft and rocking the wings—to ensure water is removed. Because the laboratory samples were collected prior to such a specialized procedure, investigators could not rule out that water contamination might have occurred and subsequently cleared during the pilot's standard pre-flight drain.