What happened
On July 3, 2025, during a flight test program at the Aleksandrowice (EPBA) aerodrome, a Diana 4E glider, registration SP-GKMB, operated by "Avionic" Sp. Jawna, experienced a significant technical failure. While flying at approximately 2,000 meters AGL at speeds near the Never Exceed Speed (VNE), the aerodynamic airbrakes deployed and became stuck in the open position. The pilot was unable to close them, which significantly increased the aircraft's sink rate and reduced its glide range.
Following the failure, the pilot informed a ground engineer, who advised aborting the test and returning to the aerodrome. During the descent, the pilot joined the traffic pattern at approximately 220 meters AGL. However, the pilot failed to follow the engineer's instruction to turn back toward the airfield and instead continued flying straight. Realizing the glider could not reach the runway due to the high sink rate caused by the open airbrakes, the pilot attempted an emergency landing in a field near a horse riding arena located in front of the aerodrome.
During the final approach, the glider flew near buildings and a person on horseback. The aircraft entered a stall, losing lateral, longitudinal, and directional stability. The glider subsequently struck obstacles at the riding arena and hit the ground. The pilot sustained light injuries and was able to exit the cockpit independently.
The investigation
The PKBWL investigation focused on the mechanical failure of the airbrake system and the pilot's performance. Investigators examined the airbrake mechanism and determined that the failure was caused by the upper plate jamming against the middle plate. This occurred because high transient stresses during the sudden deployment caused the plates to shift out of alignment. The investigation also included a blood alcohol test, which revealed that the pilot was intoxicated at the time of the accident.
Findings
- The primary cause of the accident was the pilot's loss of situational awareness, driven by alcohol impairment, lack of experience with the specific aircraft, and stress from the technical failure.
- The airbrake malfunction, while a contributing factor that limited the glider's glide performance, was not the sole cause of the crash; the investigation concluded that a safe landing at the aerodrome was still possible despite the malfunction.
- The pilot failed to plan an appropriate landing maneuver that accounted for the increased sink rate.
- The pilot did not follow the ground engineer's instructions to return to the airfield.
- The pilot attempted a landing in extremely difficult terrain without sufficient airspeed and with flaps set at +15 degrees, leading to a stall and subsequent spin/spiral dive.
- The pilot's state of intoxication disqualified him from performing flight duties and directly contributed to the poor decision-making and loss of situational awareness.