What happened
On June 10, 2012, an L-29 Delfín, registration OK-ATS, was performing a planned introductory flight at the Žatec/Macerka airport (LKZD) to familiarize a passenger with the aircraft's handling during aerobatic maneuvers. The flight, operated by Aviation Technologies and Services, s.r.o., consisted of a series of complex vertical and horizontal maneuvers, including loops, rolls, and half-cuban eights.
During the final sequence of maneuvers, the pilot attempted a high-energy vertical maneuver. While attempting to recover from the top of the maneuver, the aircraft entered a state of near-stall, leading to a significant drop in the nose. This transitioned into an uncontrolled spiral dive with high angular rates. The aircraft descended rapidly at a very steep angle, striking the ground approximately 500 meters south of runway 29. The impact caused the aircraft to bounce and continue forward for 253 meters before the nose struck the ground again. A post-impact fire, fueled by released fuel, completely destroyed the aircraft. Both the pilot and the passenger sustained fatal injuries.
The investigation
The ÚZPLN investigation utilized video footage from a camera mounted on the aircraft's keel, radar data, and witness statements from the AFIS dispatcher. The investigation examined the pilot's flight profile, the aircraft's airworthiness, and the compliance of the flight with established safety limitations. Radar analysis confirmed that the aircraft's altitude during several segments of the flight was below the minimum altitudes required for VFR flight and below the specific vertical limits set in the pilot's Special Flight Authorization.
Findings
- The pilot was qualified and medically fit, but had not flown this specific aircraft type for six months, which may have affected his proficiency in executing advanced aerobatic elements.
- The pilot performed aerobatic maneuvers in violation of the vertical and horizontal altitude restrictions specified in his Special Flight Authorization.
- The flight was conducted at altitudes below the minimum allowable VFR altitude.
- The pilot failed to manage the aircraft during a complex maneuver, leading to an uncontrolled spiral dive at an altitude lower than permitted.
- The aircraft was fully destroyed by the impact and subsequent fire.
- The operator failed to provide required documentation regarding the procedures for carrying additional persons on board.