What happened
On July 4, 2016, a pilot was conducting a cross-country flight in an L 13A Blaník, registration OK-0931, accompanied by a passenger. The flight began with a tow from Brno-Medlánky (LKCM) to Moravská Třebová (LKMK). While initial thermal conditions were favorable, the pilot was unable to maintain lift upon reaching the turning point, necessitating a landing at LKMK. After being re-towed into stronger thermals, the pilot continued the flight toward the northern edge of the LKCM control zone.
As the flight progressed, thermal conditions deteriorated. While flying near Bořitov, the pilot observed convective cloud formation near Kuřim and attempted to locate rising air. However, the lift was insufficient, gaining only approximately 20 meters over seven minutes. Finding himself with insufficient altitude to reach the intended aerodrome, the pilot decided to perform a field landing. He selected a wheat field near the village of Česká, noting that surrounding areas were covered in tall beet crops and would be unsuitable.
During the landing approach at approximately 250 meters AGL, the pilot encountered a significant lateral slope in the field. As the glider touched down, the left wing caught in the tall wheat, causing the aircraft to rotate approximately 160 degrees. To protect the tail surfaces, the pilot pushed the nose down during the rotation. The aircraft sustained damage to the center section due to centrifugal forces during the sudden rotation.
The investigation
The ÚZPLN investigation examined the pilot's decision-making process, the meteorological conditions, and the aircraft's mechanical state. The investigation established that the pilot was fully qualified and the aircraft was airworthy with valid inspections. The investigation focused on why the pilot's search for thermals led to a situation where a field landing became the only viable option.
Findings
- The pilot misjudged the availability of thermal lift in the area near Kuřim.
- The search for rising air resulted in a loss of altitude that prevented a return to the aerodrome.
- The pilot's decision-making led to a situation where he was forced to land in a field with tall crops.
- The lateral slope of the chosen field and the resistance from the wheat caused the left wing to snag, triggering the rotation.
- All structural damage to the L 13A Blaník was caused by centrifugal forces during the sudden rotation.