What happened
On April 30, 2005, a Rolladen-Schneider LS-7wl glider, registration D-8178, departed from the Évora Aerodrome via aero-tow at approximately 11:15 UTC. The pilot initially reached altitudes between 2,000 and 3,000 feet AGL by utilizing weak thermal convection.
Approximately 30 minutes into the flight, the pilot observed an increase in cloud cover and a cessation of thermal activity. Attempting to return to the aerodrome, the pilot encountered sustained sink rates of 300 to 400 feet per minute. These descending air currents prevented the aircraft from maintaining the minimum safe altitude required to reach the airfield. Consequently, the pilot elected to perform a precautionary landing in a nearby cereal field. The pilot selected the site based on its flat appearance, lack of visible obstacles, and favorable wind conditions. While the landing was controlled and smooth, the aircraft's landing gear and right wing sustained minor damage after striking stones, measuring 20 to 30 cm in diameter, which were hidden beneath the dense crop.
The investigation
The GPIAAF investigation examined the flight sequence, meteorological conditions, and the pilot's decision-making process. The investigation confirmed that the pilot and the aircraft held all necessary valid documentation and that the initial meteorological forecast had predicted favorable conditions for soaring. The investigators also evaluated the landing site selection, noting that the pilot had properly assessed the terrain's slope, wind orientation, and lack of obstacles prior to the touchdown.
Findings
- The primary cause of the incident was deficient flight planning by the pilot, as the precautionary landing occurred only 4 km from the Évora Aerodrome.
- An unexpected change in atmospheric conditions, specifically the loss of thermal activity and subsequent sink rates, acted as a contributing factor.
- Hidden obstacles (stones) within the dense vegetation of the landing field caused the structural damage to the landing gear and right wing.
- The pilot remained uninjured during the event.