What happened
On July 15, 1972, at approximately 11:04 AM, two Cessna 150 aircraft, registered as HB-CUO and HB-CSK, collided in the airspace over Sanetto, near Magadino, Switzerland.
The pilot of HB-CSK was performing a solo training flight, having previously completed several circuits with an instructor. After receiving instructions from the Locarno airfield manager to return and land because the aircraft was reserved for another client, the pilot entered the downwind leg of runway 26 at an altitude of approximately 1,700 feet. During this maneuver, the aircraft struck another plane from below.
Simultaneously, the pilot of HB-CUO was returning from a cross-country flight to Sion. As HB-CUO approached the Locarno airfield, it collided with HB-CSK at an altitude of roughly 300 meters. The impact was severe; the propeller of HB-CSK struck the cockpit area of HB-CUO and severed the control cables for the ailerons and flaps on the left wing. This caused the left wing of HB-CUO to detach, sending the aircraft into a fatal spiral dive. The pilot of HB-CUO was killed upon impact.
For HB-CSK, the collision caused significant damage to the tail section, including the destruction of the left elevator and interference with the rudder movement. Despite the loss of control effectiveness, the pilot managed to execute an emergency landing. However, the aircraft caught fire upon impact with the ground and was destroyed. The pilot of SB-CSK escaped the wreckage without injury.
The investigation
An investigation conducted by the Swiss Transportation Safety Investigation Board (SUST) examined the wreckage, witness statements, and flight records. Witnesses observed that HB-CUO appeared to be climbing and overtaking HB-CSK from a lower position. One witness noted that the aircraft were flying at nearly the same altitude and that the overtaking aircraft had higher engine power.
Technical analysis of the wreckage confirmed that the propeller of HB-CSK caused the structural failure of the left wing on HB-CUO. The investigation also noted that HB-CUO was not equipped with a radio, whereas HB-CSK was equipped with a VHF radio tuned to the airfield frequency.
Findings
- The primary cause of the accident was inadequate airspace surveillance by the pilot of HB-CUO.
- The pilot of HB-CUO may have been distracted by focusing on landing conditions, such as wind strength and direction, or by monitoring other nearby traffic.
- The pilot's ability to maintain visual lookout was hindered by significant blind spots.
- Both pilots had relatively limited flight experience, with approximately 30 hours of flight time each.
- The lack of active air traffic control services at the airfield during the time of the accident contributed to the risk, as the pilot of HB-CSK could not have been directed via radio to avoid the conflict.