What happened
On September 10, 2018, an Aeropro Fox ultralight aircraft, registration SP-STYL, was performing technical flights for airworthiness certification at the Ręczaje Polskie landing field near Wołomin, Poland. During the fourth flight of the day, while on final approach to runway 020 at an altitude of approximately 50 meters, the pilot experienced a sudden and severe cramp in his left calf.
The physical pain and the resulting difficulty in maintaining precise control caused the aircraft to drift left. The left main landing gear struck the ground before the runway threshold, hitting an area characterized by uneven terrain, including ruts and molehills, at a speed slightly higher than the normal landing speed. The pilot immediately increased power and executed a go-around.
Upon realizing that the left landing gear was displaced at an angle of approximately 20-20 degrees, the pilot decided to land on an ungrassed section of the field before the runway threshold. This decision was made to utilize the softer terrain to better absorb the impact and to avoid a potential ground loop on the paved runway, given the existing gear damage and variable winds. The pilot performed the landing with minimal flaps and low speed, cutting the engine before touchdown. The aircraft tilted left and came to a stop after a short roll. The landing gear legs were broken near the wheel axis, and one propeller blade was damaged.
The investigation
The PKBWL investigation established that the pilot was fully qualified and experienced, with approximately 500 hours on ultralight aircraft. The investigation confirmed that the pilot had properly notified FIS Warszawa of his intention to fly without radio communication and that all flight parameters, including weight and center of gravity, were within limits. The aircraft was found to be in good technical condition, and the weather conditions, while involving variable winds, were suitable for flight. The investigation also verified that the pilot was not under the influence of alcohol and had followed proper emergency procedures, including shutting off the fuel valve and engine before exiting the aircraft.
Findings
- The primary cause of the incident was pilot error resulting from a sudden physical impairment (a severe leg cramp) that hindered the ability to control the aircraft.
- Locally variable wind conditions contributed to the difficulty in maintaining the flight path.
- The pilot's decision to land on the uneven terrain before the runway threshold was considered correct, as it helped mitigate the severity of the impact and prevented a potential ground loop.