What happened
On July 11, 2015, at approximately 08:19 UTC, an L-13A Blaník glider, registration OK-2XXXXXXXXXXXXXXXX (Note: source specifies OK-2722), was performing training maneuvers at Plasy Airport (LKPS). The flight, operated by Aeroklub Plasy, was part of a structured training syllabus involving the practice of correcting faulty landings, specifically simulating a ground loop.
During the flare phase of the approach, the instructor intentionally manipulated the control column to demonstrate the glider's behavior during a simulated ground loop. In response to this input, the student pilot reacted by abruptly pushing the control column forward while simultaneously closing the airbrake flaps. This sudden maneuver caused the glider to enter a steep descent. Although the instructor immediately attempted to correct the pitch by pulling back on the control column and securing the airbrakes, the low altitude prevented a successful recovery. The glider's main landing gear struck the grass runway 150 meters from the threshold of Runway 21 with significant force.
The investigation
The ÚZPLN investigation focused on the sequence of control inputs and the effectiveness of the instructor's intervention. The investigation confirmed that the aircraft was airworthy, with its most recent annual inspection completed in May 2015, and the crew held valid medical and flight qualifications. The investigation also reviewed the mechanical damage, which included deformation of the lower fuselage skin and damage to the landing gear attachment points. Post-accident inspections by a maintenance organization resulted in the replacement of several components, including the landing gear strut, shock absorber, and various structural members.
Findings
- The student pilot correctly managed the airbrake flaps but reacted to the simulated error with an inappropriate and abrupt forward pressure on the control column.
- The instructor's demonstration of the simulated ground loop triggered the student's instinctive, heavy-handed response.
- The instructor failed to take timely corrective action following the student's sudden input to counteract the steepening descent.
- The low altitude at the time of the maneuver left insufficient margin for the instructor to prevent the impact.
- All structural damage to the L-13A Blaník was directly caused by the high-energy impact with the ground.