What happened
On June 17, 2012, at approximately 08:53 UTC, an Alexander Schleicher K 7 glider, registration OK-4069, was performing a training maneuver at Slaný Airport. The flight was part of a student's training program for glider pilot qualification, specifically practicing the recovery from faulty landings. The aircraft was being towed to a critical flight phase using an aero-tow.
During the maneuver, the instructor simulated a "ballooning" effect by pulling back on the controls and then releasing the stick. The student reacted by aggressively pushing the controls forward and applying air brakes. While the instructor attempted to correct the student's reaction by pulling back on the controls again, the low altitude prevented a successful recovery. Consequently, the glider stalled and struck the runway with significant force on its main landing gear.
There were no injuries to the student or the instructor. However, the impact caused structural damage to the fuselage frame and the fabric covering behind the rear cockpit.
The investigation
The ÚZPLN investigation examined the flight profiles, the training syllabus, and the experience levels of the crew. The investigation established that the student and instructor were both properly licensed and medically fit for the flight. The aircraft was also found to be airworthy and maintained according to regulations.
The investigation noted that while the instructor had significant total flight time, they had relatively little experience specifically with the K 7 type, having only transitioned to this model a few months prior to the accident. The investigation also found that the training syllabus does not specify a precise altitude for practicing landing error recoveries, leaving the decision to the instructor's judgment and the student's skill level.
Findings
- The primary cause of the accident was the instructor's incorrect estimation of the altitude required to perform the landing error recovery maneuver, which left insufficient margin to counteract the student's aggressive control inputs.
- The student's energetic reaction to the simulated ballooning led to a stall at an altitude too low for recovery.
- Meteorological conditions were favorable (CAVOK) and did not contribute to the event.
- The aircraft's structural damage was a direct result of the forces generated during the hard landing on the main gear.