What happened
On March 12, 2012, a Pioneer 200, registration CS-UPK, was conducting a recreational flight from Torres Vedras to Coimbra. While cruising at approximately 400 feet, the engine began to fail, exhibiting intermittent power delivery that fluctuated with throttle adjustments before eventually losing responsiveness.
The pilot identified a suitable landing site in a field near Pé da Pedria, Alcanede, and performed an emergency landing. Although the touchdown was smooth, the uneven terrain caused the nose gear to collapse. The impact damaged the propeller, deformed the engine mount, and caused abrasions to the underside of the left wing. Both occupants escaped the incident without injury.
The investigation
The GPIAAF examined the aircraft's engine and fuel system. While the engine functioned normally when fueled directly via the carburetor, it failed once the fuel supply was drawn from the tanks. Investigators discovered a significant amount of solid debris at the bottom of an auxiliary fuel tank, which had obstructed the fuel pickup tube.
The investigation also noted that the aircraft featured an auxiliary 17-liter tank that lacked a fuel quantity indicator and a drain valve, making it difficult to detect contaminants or monitor fuel levels. Furthermore, the aircraft had recently undergone an extensive engine overhaul, but the fuel system had not been thoroughly inspected following the period of inactivity.
Findings
- Fuel contamination caused the engine power loss, as solid deposits in the auxiliary tank blocked the fuel flow.
- The collapse of the nose gear was caused by the irregularities of the landing terrain.
- The pilot's decision to land with flaps retracted (per procedure) resulted in a higher approach speed, which contributed to the nose gear failure upon hitting the uneven ground.
- Inadequate maintenance or refueling practices allowed contaminants to accumulate in the fuel system.
- The auxiliary tank design lacked necessary features, such as a drain valve or quantity gauge, to facilitate fuel management and contamination removal.