What happened
On July 16, 2008, at approximately 13:00 UTC, a TL-30 and00 Sirius ultralight aircraft, registration OK-NUA 22, crashed into a field southwest of Hradec Králové airport (LKHK). The aircraft was being operated by TL-ULTRALIGHT, s.r.o.
Witnesses observed the aircraft flying at an altitude of approximately 250 to 300 meters. The flight transitioned from level flight into a climb with the engine at idle power. Following a significant reduction in airspeed, the aircraft entered a state of rotation, described by witnesses as either a spin or a steep spiral. The rotation became increasingly intense until the aircraft impacted the ground. There were no visible signs of structural failure prior to the impact, and the pilot did not attempt to deploy the aircraft's ballistic parachute system. The impact was followed by a post-crash fire that completely destroyed the aircraft and caused damage to nearby crops. The pilot sustained fatal injuries.
The investigation
The ÚZPLN investigation examined the aircraft's flight characteristics, the pilot's actions, and the aircraft's configuration. Technical analysis by the Brno University of Technology assessed the aerodynamic stability of the TL-3000 Sirius, noting that distinguishing between a spin and a steep spiral can be extremely difficult even for experienced pilots.
Investigators also reviewed the aircraft's maintenance and regulatory status. It was noted that the aircraft had not yet undergone the required procedures for official flight authorization by the LAA ČR, and no insurance had been arranged for this specific flight. Furthermore, the investigation found that the transport lock on the GRS 6/473SD Speedy ballistic parachute system had not been removed following its installation.
Findings
- The primary cause of the accident was the unauthorized entry into a flight regime (spin/steep spiral) at a low altitude and the subsequent failure to recover the aircraft.
- The pilot likely failed to clearly distinguish between a spin and a steep spiral, rendering recovery techniques potentially ineffective.
- Performing such maneuvers at an altitude of only 300 meters was considered irresponsible, especially given the unverified flight characteristics of the aircraft.
- The ballistic parachute system would have failed to deploy even if activated because the transport lock remained in place.
- The aircraft was being operated without the necessary flight authorization or insurance.