What happened
On 4 August 2018, a Junkers Ju 52/3m aircraft, registered HB-HOT, departed from Locarno Aerodrome for a visual flight rules (VFR) flight toward Dübendorf. The aircraft was operated by Ju-Air and carried a total of 20 fatalities.
Following takeoff, the flight proceeded through the Blenio valley and entered the Lago di Luzzone reservoir area. During this portion of the flight, the aircraft flew at low altitudes, occasionally maintaining minimal lateral separation from the terrain. As the flight continued east through the Surselva region, the aircraft climbed to approximately 2,500 meters AMSL before performing a series of maneuvers near the basin southwest of Piz Segnas.
While navigating the valley, the aircraft's flight path began to descend. During a transition between a right turn and a left turn, the aircraft's pitch and flight path angles became increasingly negative. The aircraft entered a steep left roll that continued despite aileron corrections. This was followed by a downward spiral characterized by low-frequency vibrations and an increasing bank angle. Shortly after 16:57, the aircraft struck the ground in a nearly vertical attitude at a speed of approximately 200 km/h. The impact destroyed the aircraft, though no fire occurred.
Findings
Reconstructions of the flight path indicated that the aircraft's longitudinal axis was pointing 68 degrees downward at the time it was 108 meters above the ground. At the time of the accident, the center of gravity was located 2.071 meters behind the leading edge of the wing. Internal footage showed no movement of passengers or crew within the cabin during the period leading up to the terminal spiral.