What happened
On October 21, 2023, at approximately 09:30 UTC, a Tanarg neo 912S/BioniX2 motorized hang glider, registration OK-BZW 01, was performing a scheduled 20-minute joyride near Nymburk, Czech Republic. The flight, operated by a flight training center, was carrying the pilot and one passenger.
After taking off from Nymburk airport, the aircraft flew along the Labe river toward Poděbrady. Upon returning toward Nymburk, the pilot initiated a 180-degree right turn, followed by a transition into a left turn. During this left-hand maneuver, the aircraft entered a steep left spiral dive. The aircraft descended rapidly, losing approximately 190 meters of altitude within seven seconds, with a vertical descent rate reaching 48 m/s. The aircraft struck the left bank of the Labe river near the Nymburk lock. The impact caused a fuel explosion and a subsequent fire that destroyed the aircraft. Both the pilot and the passenger died at the scene.
The investigation
The ÚZPLN investigation utilized data from the pilot's smartwatch, witness statements, and on-site wreckage examination. Investigators examined the engine, the fuel supply, and the pilot's experience level. Technical analysis of the engine revealed no mechanical failure, though investigators found mechanical impurities in the fuel stored in the operator's canister, which could have affected engine performance. The investigation also considered the possibility of pilot interference by the passenger, noting that the passenger may have instinctively grabbed the dual controls during the sudden onset of the spiral.
Findings
- The primary cause of the accident was uncontrolled piloting during a left turn, which resulted in the aircraft entering a steep spiral dive that could not be recovered due to insufficient altitude.
- The pilot, while qualified, had only five months of experience and was not considered an appropriate candidate for conducting joyrides with passengers.
- The pilot allowed the passenger to attempt to pilot the aircraft despite lacking instructor qualifications.
- Contaminated fuel containing mechanical impurities was present in the operator's supply, which may have caused engine instability during the critical phase of flight.
- The pilot likely attempted to recover the aircraft from the spiral rather than activating the ballistic parachute system.
- The aircraft was in a valid technical condition, and weather conditions were optimal for flight.