What happened
On July 28, 2005, at approximately 15:30 UTC, two Zlin Z 50 LX aircraft, registrations OK-XRA and OK-XRB, were engaged in a formation flight for practical training near Jaroměř (LKJA). The flight involved practicing a specific aerobatic maneuver, specifically a loop (inverted loop) from the rear.
During the maneuver, the lead aircraft (OK-XRA) was being followed by the trainee aircraft (OK-XRB), which was positioned to the right and slightly behind the leader. At the top of the loop, the pilot of the lead aircraft checked the position of the trailing aircraft, reduced throttle, and radioed "continuing" to the trainee. As the formation transitioned into a vertical descent, the trainee aircraft began to drift laterally toward the lead aircraft.
In an attempt to correct the lateral movement, the trainee pilot applied right rudder; however, this was ineffective. To avoid a further collision, the trainee pilot executed a sudden forward push to break the maneuver. This resulted in a mid-air collision between the two aircraft. Both aircraft remained fully controllable following the impact, and both pilots were able to land safely at the departure airfield.
No injuries were reported among the crews of either aircraft.
The investigation
The ÚZPLN investigation established that both pilots held valid commercial pilot licenses (CPL) and appropriate medical certifications. The aircraft were maintained in accordance with the manufacturer's instructions and were fully airworthy prior to the flight. The weather conditions at the time of the accident were CAVOK with light winds, which were suitable for the intended flight activities. The investigation focused on the sequence of the maneuver and the flight path of the trailing aircraft during the transition from the top of the loop to the descent phase.