What happened
On April 23, 1993, at approximately 15:25, a glider pilot was participating in a winch-launch training week at the Ambri military airfield. The aircraft, an ASW 20L with registration HB-1476, was launched using a winch system. Following the initial transition phase, the glider began a climb while executing a left-hand turn, reaching an altitude of approximately 50 meters. As the turn continued, the aircraft failed to respond to any control inputs and subsequently entered a near-vertical descent, impacting the ground near the paved runway. The pilot, who had extensive motor flight experience but relatively limited experience with winch launches, sustained fatal injuries in the impact. The aircraft was destroyed.
The investigation
The investigation, conducted by the Swiss Transportation Safety Investigation Board (SUST), examined the aircraft's mechanical condition, the pilot's medical history, and the circumstances of the flight. Physical inspection of the ASW 20L revealed no evidence of pre-existing mechanical failures in the control linkages, cables, or pulleys. The aircraft's weight and center of gravity were within permissible limits.
Medical examinations of the pilot provided critical insights. An autopsy revealed extensive internal trauma, including severe damage to the heart, lungs, and liver. While a fresh myocardial infarction could not be macroscopically confirmed due to the severity of the impact, the presence of an extensive old infarct and significant coronary artery disease was noted. Forensic evidence, including the lack of defensive posturing and the absence of pulmonary fat embolism, suggested the pilot may have been incapacitated or deceased even before the moment of impact.
Findings
- The primary cause of the accident was the loss of control of the glider, which was likely due to a medical emergency.
- The pilot had a history of coronary artery disease and had undergone medical treatment for related issues, including a previous myocardial infarction.
- There was no evidence of technical malfunction or pilot error in the aircraft's control systems.
Safety action
- There is a critical need to close the information gap between treating physicians and the medical examiners of the Federal Office of Civil Aviation (FOCA).
- To ensure public safety, any physician treating a pilot for an illness or injury that could pose a risk to flight safety should be obligated to notify the FOCA medical service, similar to requirements in road traffic regulations.