What aircraft was involved and where did it happen?

The accident on 2006-09-03 involved a Straton D8, registration OK-YUU, at 1 km N Chornice, CZ.

What was the probable cause of the accident?

The accident was caused by the pilot's inability to maintain sufficient airspeed and control during the transition to a glide following an engine failure, compounded by the decision to perform a turning maneuver at an altitude too low to recover from the resulting stall.

Fatal engine failure leads to ultralight crash near Chornice

A pilot died following the engine failure and subsequent stall of a Straton D8 ultralight aircraft during a climb near Chornice, Czech Republic.

What happened

On September 3, 2006, at approximately 12:50 UTC, an amateur-built Straton D8 ultralight aircraft, registration OK-YUU, crashed approximately 1 km north of Chornice, Czech Republic. The pilot had recently completed engine and propeller installation on the aircraft. During a ground test prior to takeoff, the pilot noted insufficient engine cooling and performed minor adjustments to the spark plug mounting.

Following takeoff from an unapproved grass strip, the aircraft entered a climb at a 20-degree angle. At an altitude of approximately 30 to 40 meters, the engine suddenly failed. In response to the power loss, the pilot initiated a right-hand turn, likely attempting to return to the departure site. During this maneuver, the aircraft entered a steep bank and a rapid descent. The right wingtip struck the ground, causing the aircraft to impact the terrain at a steep angle. The impact resulted in the destruction of the cockpit and the separation of the wing. The pilot was extricated from the wreckage by witnesses but succumbed to fatal injuries during medical transport to a hospital in Brno.

The investigation

An investigation by the ÚZPLN, in cooperation with the LAA ČR, focused on the engine's condition and the pilot's maneuvers. Investigators examined the engine, which had been assembled from used parts and modified to increase displacement. Post-accident analysis of the engine revealed that cylinder number 2 had partially seized, causing the total engine failure. Additionally, the investigation found that the ignition grounding for cylinder number 1 was interrupted. The aircraft was found to have an expired technical certificate and lacked valid insurance at the time of the accident.

Findings

The pilot failed to recognize that the engine's performance, following amateur modifications, did not meet operational requirements for flight.
The pilot attempted to fly the aircraft despite having observed engine irregularities during ground testing.
The engine failure was caused by the partial seizure of cylinder number 2, with the engine likely operating on only one cylinder during the climb.
The pilot's decision to execute a turn back to the departure site, rather than utilizing the available landing area ahead, led to a loss of airspeed and a subsequent stall.
The aircraft's engine installation did not comply with technical operational standards.