What happened
On July 19, 2014, during the Kroměříž Cup aerobatic competition, a Z 526 F aircraft, registration OK-RKR, was performing a pre-planned sequence of maneuvers in the Sportsman category. The aircraft entered the fourth element of the sequence—a loop with a snap roll at the top—at an estimated altitude of 1,200 m AGL and a speed of approximately 250 km/h.
During the execution of this maneuver, the pilot initiated the snap roll too early, before reaching the top of the loop. This resulted in a loss of airspeed and a transition into an unintentional inverted (tail) spin to the right. While the pilot attempted to manage the situation by reducing engine power, the aircraft remained in an unstable, autorotative state. The longitudinal axis of the aircraft oscillated significantly, and the pilot did not execute the standard recovery procedures. The aircraft continued in the inverted spin until it struck the ground at a steep angle, approximately 0.5 km southeast of LKKM, in an inverted position. The impact was followed by an immediate post-crash fire, which destroyed the aircraft and caused the death of the pilot.
The investigation
The ÚZPLN investigation examined the aircraft's technical condition, the pilot's flight experience, and witness testimonies from judges and safety pilots. Technical inspection of the engine, propeller, and control surfaces revealed no mechanical failures; the engine was likely operating at flight power at the time of impact. Witnesses observed that the pilot was highly experienced and had successfully performed the same sequence on the same aircraft in previous days. The investigation also analyzed the control inputs during the spin, noting that the elevator remained in a 'pushed' position and the rudder was deflected left, indicating a failure to apply the necessary recovery inputs.
Findings
- The transition from a normal snap roll to an inverted spin was caused by a combination of low airspeed and unfavorable control inputs during the maneuver.
- The pilot failed to recover from the inverted spin, likely due to an error in identifying the type of spin or due to the effects of stress.
- The aircraft was in good mechanical condition, and the pilot possessed the necessary qualifications and recent experience for the maneuver.
- The fatal impact and subsequent fire were the direct results of the uncontrolled descent into the terrain.