What aircraft was involved and where did it happen?

The accident on 2014-08-15 involved a VL-3, at Třebovice, CZ.

What was the probable cause of the accident?

The investigation could not definitively identify a single cause for the aircraft's sudden descent, but noted that the aircraft was overweight and the crew was experiencing extreme stress during the final moments of flight.

Fatal Ultralight Crash Near Třebovice Under Investigation

A JMB Aircraft VL 3 crashed near Třebovice, Czech Republic, resulting in two fatalities and the destruction of the aircraft.

What happened

On August 15, 2014, a VL 3 ultralight aircraft, registration OK-LUU05, crashed west of the village of Třebovice, Czech Republic, during a low-altitude flight. The aircraft departed from the LKUO airfield on a training flight, initially heading toward Česká Třebová.

GPS data and engine monitoring records indicate that after an initial climb, the aircraft entered a steady descent. During the final stages of the flight, the aircraft's airspeed fluctuated, and engine RPM varied. Witnesses on the ground reported seeing the aircraft flying at a very low altitude, approximately 30 meters above the trees, near high-voltage power lines. One witness observed the aircraft perform a sudden, violent maneuver, pitching up sharply before flipping over and plunging vertically toward the ground. The impact resulted in the two fatalities of the pilot and the passenger, and the total destruction of the aircraft.

The investigation

The ÚZPLN investigation examined the wreckage, engine components, and cockpit instrumentation, including a recently installed airspeed indicator. The committee also analyzed GPS flight tracks, engine performance logs (TL-3/724_RTX), and several eyewitness accounts.

Technical inspections of the engine and flight controls found no evidence of mechanical failure or malfunctions in the fuel, oil, or electrical systems. While the aircraft was found to be overweight by approximately 36.3 kg (plus the weight of unquantified fuel), investigators could not find a specific mechanical trigger for the loss of control. The investigation also noted that the pilot and passenger experienced intense psychological stress and a severe stress reaction in the seconds leading up to the impact, though they remained conscious and were not under the influence of any prohibited substances.

Findings

The primary cause of the accident was the unexplained fall of the aircraft.
The low altitude at the time of the incident left the pilot with no possibility to recover from the descent.
The aircraft was operating in an overweight condition, exceeding its maximum takeoff weight.
The crew experienced a prolonged period of intense stress and negative emotions immediately preceding the crash.
No specific mechanical or medical cause for the sudden change in flight trajectory could be definitively established.