What happened
On August 1, 2011, at approximately 12:37 PM, a Kestrel H401 glider, registration D-2197, departed from Saanen airfield for a flight toward the Valais region. Following a routine tow release at an altitude of 1,770 meters, the pilot navigated through various thermal currents.
By 1:05 PM, flight data from the onboard FLARM system indicated the aircraft was near the Chrine Pass. Shortly thereafter, eyewitnesses observed the glider entering a steep, nose-down turn at a very low altitude. The aircraft plummeted vertically toward a group of trees, striking the ground with such force that the nose of the fuselage embedded 1.5 meters into the soft earth and one wing was torn from the airframe. The pilot, a highly experienced glider pilot, was the sole occupant and was killed in the impact.
The investigation
Investigators from SUST examined flight data from the damaged FLARM unit, analyzed meteorological conditions, and reviewed the aircraft's maintenance and weight records. The investigation also included an autopsy of the pilot and interviews with eyewitnesses and the pilot's family.
Technical analysis of the Kestrel H401 revealed that the aircraft was in a configuration suitable for high-speed flight, with the camber flaps set to position -1. The aircraft's center of gravity was found to be slightly behind the allowable limits, though the overall mass was within permissible bounds. Investigators also reviewed the pilot's medical history and recent flight logs to determine if any external factors contributed to the loss of control.
Findings
- The aircraft struck the terrain in a vertical dive at a speed below the minimum flight velocity.
- The loss of control was likely caused by sudden and complete incapacitation of the pilot due to an acute cardiovascular event.
- An autopsy revealed significant pre-existing pathological changes in the heart muscle and coronary arteries.
- While the pilot had recently passed a Class 2 medical examination, laboratory results from his primary physician had previously indicated an increased cardiovascular risk.
- There were no evidence of mechanical failure or technical defects in the aircraft prior to the impact.