What happened
On November 24, 2008, a Socata TB 200, registration CS-DEG, operated by Academia Aeronáutica de Évora, was conducting a dual-instruction flight near Évora, Portugal. The flight, commanded by an instructor pilot and a student pilot, was part of a planned mission between Évora and Arraiolos.
During the approach phase, while the aircraft was on the base leg of the landing pattern, the instructor pilot reported a partial loss of engine power to the tower, stating that the aircraft would be unable to reach the runway. The instructor took control of the aircraft, executed a shortened pattern to the final approach, and followed the appropriate emergency procedures. The crew successfully performed an emergency landing in an open field parallel to the runway. There were no injuries to the two occupants, and the aircraft sustained no damage.
The investigation
The GPIAAF investigation examined the engine, the flight conditions, and the crew's actions. Ground testing of the Lycoming IO-360 engine revealed no mechanical defects or power deficiencies. The investigation focused on environmental factors and operational procedures during the descent from 4,000 feet to the circuit altitude.
Investigators analyzed the meteorological conditions, noting that the cloud base was at 4,000 feet and the air temperature at that altitude was approximately 5°C. The investigation also considered the impact of significant tailwinds and the aircraft's configuration during the descent.
Findings
- The aircraft was flying in conditions conducive to ice formation in the fuel filter, as the temperature at the cloud base was near the threshold for icing.
- There was a high probability of spark plug fouling due to excessive use of low power settings during the descent.
- The presence of moderate to strong winds (gusting up int 20-25 knots) increased the aircraft's ground speed, which may have influenced the crew's decision-making regarding the descent profile.
- The investigation noted that the crew's approach to the base leg should have been anticipated earlier to account for the wind direction and intensity, which might have allowed for a runway landing even with partial power loss.