Glider Collides with Tree During Off-Field Landing in Thorame-Basse

Casualties unknown • French is the work of reference., FR

A private glider pilot sustained serious injuries after his aircraft struck a tree following a landing attempt in a sloped field.

What happened

On April 6, 2023, a LS8-e neo1 glider, registration HB-2550, was conducting a local flight after taking off from the Sisteron-Vaumeilh aerodrome. After reaching an altitude of approximately 2,863 meters, the aircraft began losing altitude at an average rate of 0.7 m/s. Upon entering the Thorame-Basse valley, the pilot attempted several spiral maneuvers to regain altitude but was unsuccessful due to encountering subsiding air on the lee side of the terrain.

Unable to maintain altitude, the pilot opted for an off-field landing in a field believed to have a slight upward slope. During the final approach, the aircraft maintained a ground speed of approximately 150 km/h. As the pilot attempted to flare, the central landing gear and the left wing made contact with the ground. The glider bounced and continued along the field before violently striking a tree, eventually coming to a halt in a lower field.

The investigation

The investigation, supported by data from the aircraft's LX9000 onboard computer, focused on the meteorological conditions and the pilot's approach. Investigators examined the terrain and wind patterns, noting that 20 to 30 knot winds from the northwest were creating significant downdrafts in the area. The investigation also reviewed the pilot's decision-making regarding the landing site and the use of available safety resources, such as the French Glider Federation's guide to safe landing areas in the Alps.

Findings

  • The pilot was flying on the lee side of the terrain, where subsiding air prevented the recovery of altitude.
  • The aircraft's ground speed during short final was significantly higher than the recommended approach speed, potentially due to a tailwind gust.
  • The pilot's attempt to land in a sloping field contributed to the loss of control during the flare.
  • The mountainous environment likely made it difficult for the pilot to accurately assess the horizon and the slope of the landing field.
  • The pilot was unaware of a designated safe landing area located only a few hundred meters from the accident site.

Probable cause

The accident was caused by the pilot's attempt to land in a sloping field while encountering descending air currents, which led to a wing strike during the flare and a subsequent collision with a tree.

Frequently asked questions

What happened in the 2023-04-06 DG– LS8-e neo1 accident near French is the work of reference., FR?

A private glider pilot sustained serious injuries after his aircraft struck a tree following a landing attempt in a sloped field.

What aircraft was involved and where did it happen?

The accident on 2023-04-06 involved a DG– LS8-e neo1, registration HB-2550, at French is the work of reference., FR.

What was the probable cause of the accident?

The accident was caused by the pilot's attempt to land in a sloping field while encountering descending air currents, which led to a wing strike during the flare and a subsequent collision with a tree.

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