What happened
On August 1, 2019, at approximately 09:35 LMT, a Letov ST-4 Aztek, registration SP-SPIM, departed from an airfield in Kłobuck with the intention of flying to Konopiska. The purpose of the flight was to familiarize a passenger with the aircraft's flight characteristics.
While the flight initially proceeded normally, the engine began to operate irregularly approximately seven minutes into the flight. The engine RPM first fluctuated between 4,000 and 6,000 RPM before dropping to a range of 3,000 to 5,000 RPM. As the engine power further decreased to between 2,000 and 3,000 RPM, the aircraft began to descend at a rate of approximately 2 m/s. In response to the loss of power, the pilot decided to perform a precautionary landing in an unprepared field near Wyrazów, near Częstochowa.
During the landing maneuver, the propeller struck vegetation—specifically protruding stalks that were not visible from the air—resulting in damage to the propeller.
The investigation
The investigation focused on the sequence of engine performance degradation and the circumstances of the landing. The investigation established that the pilot held the necessary licenses for the flight and that there were no injuries to the pilot or the passenger.
Findings
- The primary cause of the incident was improper engine operation (engine malfunction).
- The aircraft was equipped with a non-certified ROTAX 582 engine.
- The propeller sustained damage due to contact with ground vegetation during the forced landing.