What happened
On February 12, 2022, an L-13 Blaník glider, registration OK-3800, was conducting a local thermal flight at Letkov Airport (LKPL) when it struck trees near the Koterov area. The flight began as a towed operation behind a Dynamic UL aircraft, climbing to approximately 900 m AGL. After several turns south of the aerodrome, the pilot joined the right-hand pattern for runway 08L.
During the fourth circuit turn, the pilot encountered significant descending air. In an attempt to manage the descent, the pilot re-engaged the air brakes and retracted the flaps. However, the aircraft had already descended below the level of the nearby Háje hill. Realizing the aircraft could not reach the runway, the pilot attempted a left-hand turn to perform a forced landing in a field near Koterov. During this maneuver, the right wingtip struck the treetops on a steep slope, leaving the glider wedged in the branches at an altitude of approximately 6 meters.
The investigation
The ÚZPLN investigation examined the flight path using OGN Glider Tracker data, witness statements from the radio dispatcher, and physical evidence from the wreckage. The investigation confirmed that the aircraft was airworthy and the pilot was highly experienced, with extensive flight time on the L-13 type. Investigators also analyzed the meteorological conditions, noting that the aircraft had flown into an unstable air mass—specifically a lee rotor—caused by southeasterly winds flowing over the steep terrain of the Úslava river valley.
Findings
- The pilot initiated the third circuit turn too late, given the prevailing southeasterly airflow.
- The pilot failed to abort the approach to the airport in a timely manner after entering unstable air.
- The decision to attempt a forced landing was made while the aircraft was already below the airfield elevation and in close proximity to the crest of a steep slope.
- The late decision to abort the approach to the airport and the subsequent unmanaged maneuver during the forced landing resulted in the collision with the obstacle.
- The impact with the trees caused extensive damage to the L-13 Blaník, including a broken fuselage, a destroyed cockpit canopy, and a damaged right wing.