What aircraft was involved and where did it happen?

The accident on 2017-10-14 involved a ROLLADEN-SCHNEIDER FLUGZEUGBAU GMBH LS 8-18, registration HB-3359, at Gebiet Tschuggentälli / Gde. Davos, GR, CH.

What was the probable cause of the accident?

The exact cause of the accident could not be determined with certainty, though the aircraft likely entered a controlled flight into terrain during a series of turns.

Fatal Glider Collision with Terrain in Graubünden

A single-seat LS 8-18 glider crashed into a rocky slope near Davos, resulting in the death of the pilot.

What happened

On October 14, 2017, an LS 8-18 glider, registration HB-3359, departed from Bad Ragaz for a recreational flight. The pilot, an experienced glider pilot with over 3,000 flight hours, intended to search for thermals. After being towed to an altitude of approximately 2,545 meters, the pilot released from the towline and proceeded to utilize various updrafts in the region.

During the final stages of the flight, the aircraft was observed circling near the Pischahorn. GPS data indicates that in the final minute of recorded flight, the pilot performed two right-hand full circles at a relatively constant altitude. During this sequence, the right winglet of the aircraft struck a rock face at approximately 2,680 meters. The impact caused the winglet and a portion of the outer wing to separate from the aircraft. The main wreckage, containing the fuselage and the left wing, slid approximately 130 meters down a debris slope to a final resting position at 2,550 meters. The pilot sustained fatal injuries in the accident.

The investigation

The Swiss Transportation Safety Investigation Board (SUST) examined the wreckage, GPS flight data from the LX9000 flight computer, and witness statements. The investigation looked into the aircraft's technical condition, the meteorological environment, and the flight path leading up to the impact. Investigators also reviewed the functionality of the aircraft's emergency locator transmitter (ELT) and the flight recorder's ability to capture data up to the moment of impact.

Findings

The aircraft was in a controlled flight into terrain (CFIT) phase during the collision.

Approximately 20 seconds before the last recorded data point, the indicated airspeed was roughly 86 km/h, which was about 10% above the relevant stall speed.

The aircraft was performing right-hand turns at a nearly constant altitude immediately prior to the impact.

The weather conditions were clear with no significant meteorological impact on the accident.

The aircraft's technical records showed no pre-existing mechanical defects or restrictions.

Safety action

Following the investigation, SUST issued a safety notice to manufacturers of flight computers and collision warning systems (such as FLARM). The notice emphasizes the need for accident-resistant flight path recording, requesting that devices be designed so that data remains recoverable even after a power interruption or physical destruction caused by an accident.