What happened
On August 27, 2016, at 16:46 UTC, two ultralight aircraft collided near the village of Dlouhá Loučka in the Olomouc region. The aircraft involved were an EV-97 Eurostar, registration OK-HUR 09, and an NG 4 VIA, registration OK-VAQ 56.
The flight was part of a group of three aircraft, which also included a Dynamic WT9 LSA, flying from Olomouc airport (LKOL) to perform a low-level flyover for a private celebration near Plinkout. Following the flyover, the aircraft were flying in formation in uncontrolled Class G airspace.
During the maneuvers, the NG 4 VIA approached the EV-97 Eurostar from below and to the left. At approximately 16:46:20, the propeller blades of the EV-97 Eurostar struck the upper rear section of the NG 4 VIA's cockpit canopy. The impact caused the NG 4 VIA to lose control and crash into the terrain at a steep angle, resulting in one fatality. The EV-97 Eurostar also suffered significant damage, including a destroyed propeller, and crashed to the ground, resulting in two serious injuries to its occupants.
The investigation
The ÚZPLN investigation examined GPS data from both aircraft, engine control unit (ECU) records, and witness statements. The investigation established that both aircraft were flying at altitudes significantly lower than the minimum required altitude for the area.
Data from the NG 4 VIA's ECU showed a significant reduction in engine power, with the throttle moving from approximately 98% to 24% just before the collision. The investigation also noted that the pilots of the EV-9 and WT9 aircraft had no verbal communication regarding the specific position of the NG 4 VIA during the maneuver, and the pilot of the EV-97 could not see the approaching aircraft due to its position below and to the left of the cockpit's field of view.
Findings
- The primary cause of the collision was the failure to maintain sufficient separation distance from the other aircraft, leading to a collision with the higher-flying aircraft.
- The collision led to a loss of control for both aircraft at a very low altitude.
- The pilots of the EV-97 Eurostar were flying below the minimum legal altitude.
- There was a lack of verbal communication between the aircraft regarding their relative positions.
- The pilot of the NG 4 VIA was unable to prevent the approach, though engine data shows a significant reduction in power prior to impact.