What happened
On May 28, 2010, during the "Karlovarský pohár" aerobatic competition at Touşim airport (LKTO), a Z 142 aircraft, registration OK-PNG, crashed shortly after takeoff. The flight was part of the "sportsman" category.
Witnesses observed the aircraft take off normally from runway 26. However, as the aircraft accelerated, the pilot began to experience significant physical resistance on the control column. The pilot radioed, "I cannot push," and subsequently announced an intention to return to the airport. During the attempt to turn back, the aircraft entered a left-hand spin at an altitude of approximately 40 to 50 meters. The aircraft struck the ground and immediately caught fire, resulting in the fatal injury of the pilot and the total destruction of the aircraft.
The investigation
The ÚZPLN investigation examined the wreckage, aircraft documentation, and witness testimonies. Technical analysis of the wreckage revealed that the longitudinal trim was set to a "tail-heavy" position. The investigation also reviewed the pilot's credentials, which included a valid PPL(A) and SEP/land qualification, and confirmed that the aircraft's maintenance and airworthiness documentation were up to date.
Flight testing was conducted on a similar aircraft type to measure the control forces required in such a configuration. The testing confirmed that while the forces did not exceed the structural limits of the aircraft, the physical effort required to push the control column exceeded the maximum ergonomic workload for a single-arm impulse for the pilot's physical position.
Findings
- The pilot failed to perform all required pre-flight checks as specified in the flight manual, specifically regarding the verification of the longitudinal trim position.
- The aircraft was configured with the longitudinal trim set to a "tail-heavy" position, which caused a significant increase in control forces as airspeed increased.
- The pilot misidentified the increasing aerodynamic forces on the control column as a mechanical control failure rather than an incorrect trim setting.
- The pilot's decision to initiate a turn back to the airport at low airspeed, combined with the heavy control forces, led to the aircraft entering a spin.