What happened
On October 4, 2008, an L-13A Blaník glider, registration OK-2720, was performing a winch-assisted training takeoff at the Hosín airfield (LKHS) in the Czech Republic. During the climb phase, the student pilot, occupying the front seat, applied excessive back pressure on the control stick, causing the aircraft to reach an abnormally high angle of attack.
As the aircraft reached the peak of its climb, the instructor, seated in the rear, attempted to intervene by instructing the student to push the stick forward and monitor the airspeed. However, the student failed to respond to these instructions. As the winch cable was released, the glider entered a left-hand spin. The instructor managed to recover the spin after one rotation, but the aircraft transitioned into a descending left-hand spiral with increasing speed. The glider eventually struck the ground approximately 300 meters from the runway axis. The impact resulted in the death of the student pilot and serious injuries to the instructor. The aircraft was destroyed.
The investigation
The ÚZPLN investigation examined the flight sequence, the aircraft's condition, and the crew's actions. Investigators reviewed the instructor's testimony, witness statements from the winch operator and ground crew, and the physical wreckage. The investigation confirmed that the aircraft's control systems and structural integrity were intact prior to the accident. Meteorological conditions were found to be favorable, with clear visibility and light winds. The investigation also noted that the student pilot had experienced a 34-day hiatus in training prior to this flight, which may have impacted his ability to manage the critical phase of the takeoff.
Findings
- The primary cause of the accident was a stress reaction of the student pilot, triggered by his inability to manage an initial control error.
- The student pilot applied excessive back pressure during the climb, leading to an aerodynamic stall.
- The student's failure to respond to the instructor's verbal commands and his physical fixation on the fully retracted control stick prevented the instructor from effectively recovering the aircraft from the spin.
- The instructor's ability to use the rudder to recover the spin was significantly hindered by the student's continued pressure on the flight controls.