What happened
On the afternoon of April 4, 1965, a glider flight from the Zwingen Gliding Group departed from Dittingen Airfield for a thermal flight toward the Blauen region. The aircraft, a Ka-8 with registration HB-630, was launched via aero-tow and successfully reached an altitude of approximately 350 meters above the airfield as it turned toward the southern slope of the Blauen hill.
Shortly after beginning circling maneuvers to gain altitude, the aircraft entered an uncontrolled and irregular spiral descent. Approximately twenty minutes after takeoff, at roughly 15:20 CEST, the glider struck the treetops on the southern slope of the Blauen and became lodged in the forest. The impact resulted in heavy damage to the aircraft.
The investigation
Investigators examined the flight path, the condition of the aircraft, and the medical history of the pilot. The investigation focused on the sudden transition from a normal climb to an uncommanded spiral dive. While the aircraft's mechanical state was not cited as a primary failure, the physical condition of the pilot was scrutinized.
Medical examinations and an autopsy were conducted to determine the cause of the pilot's incapacitation. The investigation also reviewed the pilot's recent medical history, including a previous cardiac event and subsequent clinical examinations conducted in Basel.
Findings
Post-mortem analysis revealed that the pilot suffered a rapidly fatal myocardial infarction (heart attack) while in flight. The autopsy also identified underlying coronary sclerosis that had been present for some time.
It was noted that the pilot had experienced a previous heart attack prior to his initial medical examination in 1962. Although a subsequent electrocardiogram (ECG) showed no signs of an infarct, the pilot had reportedly been advised by his physician to avoid flying, an instruction he did not follow. The investigation concluded that the sudden onset of the heart attack during the flight was the direct cause of the uncontrolled descent and subsequent crash.