What happened
On November 27, 1962, a Bücker Z 131 (registration HB-UST) departed from Bresso Airport for a local training flight. The aircraft reached an altitude of approximately 400 meters and began performing aerobatic maneuvers. During the exit of a looping maneuver, the aircraft entered a spin. The pilot attempted to recover by applying heavy pressure to the right rudder pedal and adjusting engine power and elevator controls, but the aircraft continued its descent. The aircraft ultimately struck the ground with its belly in a field near Niguarda, approximately 1 km from the Bresso airfield runway.
Both occupants of the aircraft sustained severe injuries. The pilot suffered multiple fractures to the legs and facial injuries, while the co-pilot experienced extensive leg fractures and a severe head injury that left him in a comatose state.
The investigation
The technical investigation examined the wreckage and the flight controls of the Bücker Z 131. Investigators found that the engine, fuel system, and lubrication system were all fully functional. The ignition system was operational, and the fuel tank had been ruptured only by the force of the impact. The flight controls, including the ailerons and elevators, were found to be free and functional prior to the crash.
Witness testimony and physical evidence indicated that the left rudder pedal was stuck in the far-left position during the spin. The investigation focused on why the pilot was unable to center the pedals to recover the aircraft.
Findings
Technical analysis concluded that the accident was not caused by mechanical failure. Instead, the investigation determined that the pilot likely suffered a sudden medical episode during the execution of the aerobatic maneuver.
It is believed that the pilot's left leg became extended in a specific position during the maneuver. The investigation noted that the pilot was wearing heavy rubber-soled footwear, which may have caused the rudder pedal to remain stuck against the textured metal floor or the fuselage side, despite the pilot's forceful attempts to use the right pedal to correct the flight path. The severity of the leg injuries sustained by the occupants was consistent with the physical forces of the impact and the pedal position.