What happened
On June 26, 2020, at approximately 17:50 UTC, a Diamond DA20 C1, registration SP-KPX, was conducting an instructor flight training (FI) mission following a route between EPMO, EPBC, EPPT, and EPMO. During the flight, the crew performed a simulated engine failure and emergency landing in an unprepared field. Following the exercise, the instructor commanded a go-around. However, as the pilot advanced the throttle, the engine failed.
The crew executed an emergency landing in a field situated between two rows of trees. The aircraft traveled across the soft ground, losing speed without any tendency to capsize. The crew applied the brakes, bringing the aircraft to a stop approximately 10 meters from the trees. There were no injuries to the crew, and the aircraft sustained no damage.
At the time of the incident, the aircraft was descending from approximately 1,50 and ended at 500 ft AGL. During the descent, the engine was at idle, the fuel mixture was set to rich, and the electric pump was active.
The investigation
The investigation examined the engine, a Continental IO-240-B with low-pressure fuel injection, and performed a 100-hour inspection, which revealed no mechanical malfunctions or abnormal operating parameters.
Meteorological data from the period showed that the temperature and dew point were both 18°C, indicating 100% humidity. The flight took place shortly after a brief but intense thunderstorm. The investigation focused on how these atmospheric conditions interacted with the engine's intake system during the descent phase.
Findings
- The engine failure occurred specifically when the throttle was moved to the maximum position during the descent.
- High humidity and 100% saturation created conditions highly conducive to icing.
- Throttle icing in the intake system likely occurred due to the condensation and freezing of water vapor near the throttle plate, a phenomenon that can occur even at relatively high temperatures (around 20°C) when the throttle is partially closed.
- The accumulation of ice on the throttle plate restricted airflow; when the pilot attempted to increase power, the restricted intake caused the engine to stall.