What happened
On July 29, 2021, a Fisher Flying Horizon 1 ultralight aircraft, registration OK-ZUE 25, crashed in a meadow near the village of Jablonná, approximately 6.5 km north of Příbram (LKPM). The pilot, who had built the aircraft over a four-year period, was flying the aircraft for the first time since a two-year hiatus from flying and specifically for the first time in a tailwheel configuration.
Following takeoff from a private airstrip, the aircraft was pushed slightly to the right by the wind. The pilot leveled the aircraft at an altitude of approximately 100 meters. While attempting to return to the departure site, the aircraft entered a sharp right-hand turn. During this maneuver, the aircraft abruptly pitched nose-down and entered a right-hand spin, impacting the ground and resulting in the fatal death of the pilot at the scene. The aircraft was destroyed in the crash.
The investigation
The ÚZPLN investigation examined the aircraft's construction, the pilot's flight experience, meteorological conditions, and the mechanical state of the fuel system. Investigators analyzed wreckage, witness statements, and conducted fuel flow tests. The investigation focused on why the aircraft entered the spin and whether engine performance was compromised during the critical phase of flight.
Testing revealed that the fuel system was contaminated with a granular absorbent (Absodan Plus) and that certain fuel lines were found in a kinked state. These factors significantly restricted fuel flow, reducing it to approximately one-third of its normal capacity. The investigation also noted that some engine and fuel system components showed signs of being reused.
Findings
- The pilot was performing his first flight in a tailwheel-configuration aircraft and lacked recent experience, having logged only 24 hours of flight time in the preceding two years.
- The aircraft's fuel delivery was likely compromised by contamination from a granular absorbent and kinked fuel lines, which restricted the engine's power.
- Wind conditions, specifically a southwest wind of approximately 12–14 knots, negatively impacted the aircraft's handling during the final right-hand turn.
- The pilot's decision to fly the aircraft after a long period of inactivity, combined with the lack of familiarity with the tailwheel characteristics, contributed to the loss of control.