What happened
On June 5, 2021, an SF 34 glider, registration OK-3401, was performing a training flight at Liberec airport. The flight, which included aerobatic practice, was being conducted by a pilot under the supervision of an instructor.
During the final approach to the glider strip parallel to runway 34, the pilot failed to execute the proper flare maneuver. The pilot reported that a command from the instructor to readjust the airbrake settings may have distracted him from the landing calculations. Consequently, the aircraft approached the ground at a speed of approximately 95 km/h, which was lower than the planned approach speed.
As the aircraft's nose began to pitch toward the ground, the instructor attempted to intervene by shouting a command and pulling back on the controls. While this corrected the aircraft's longitudinal attitude, the glider experienced a hard landing on its main wheel approximately 15 meters before the threshold of the glider strip.
Following the touchdown, the aircraft traveled about 10 meters before the main landing gear entered a depression in the terrain, measuring roughly 25–30 cm deep. As the aircraft attempted to exit this depression, the nose wheel dug into the edge of the uneven ground, causing the nose to pitch up violently. This resulted in a tail strike, where the rear part of the fuselage struck the ground with significant force. The aircraft was momentarily lifted about 0.5 meters into the air before coming to a rest.
The investigation
The ÚZPLN investigation examined statements from both the pilot and the instructor, aircraft maintenance records, and the physical condition of the aircraft at the site. The investigation confirmed that the pilot and instructor held valid licenses and medical certificates. The aircraft's technical condition and maintenance history were found to be in order, and meteorological conditions (CAVOK) were not a contributing factor to the event.
Findings
- The primary cause of the accident was pilot error during the landing maneuver, specifically the failure to perform a proper flare.
- A secondary contributing factor was the instructor's late reaction to the pilot's incorrect flight path.
- The low approach speed and the subsequent hard landing placed the aircraft in a position where it could encounter terrain irregularities.
- The impact with the terrain depression caused the tail strike and resulting structural damage, including delamination and cracks in the composite fuselage between the wings and the tail.