What happened
On June 18, 2016, at approximately 09:15 UTC, an L-23 Super Blaník glider, registration OK-5525, was performing a training flight at Kyjov Airport. The flight began with a tow to thermic lift; however, after approximately five minutes, the pilot failed to find sufficient rising air and decided to return to the airfield.
Upon entering the left-hand circuit for runway 33, the crew observed several other gliders on the left side of the runway. To avoid them, they decided to land on the right side of the runway, utilizing the lane reserved for powered aircraft. During the approach, the pilot in command handed control of the aircraft to the second pilot.
While executing the fourth circuit turn, the aircraft encountered a significant downdraft, with a descent rate of approximately 4–5 meters per second. The pilot, believing the aircraft would still reach the runway safely, retracted the braking flaps. As the aircraft approached the airfield, the airspeed dropped to approximately 70 km/h, which was below the recommended approach speeds. The glider's tail struck a field of tall oilseed rape approximately 20 meters before the runway threshold. This contact caused the aircraft to decelerate abruptly, leading the nose to strike an earthen berm bordering the airfield. The impact caused the aircraft to bounce and come to rest on the airfield, rotated approximately 90 degrees to the left.
The investigation
The ÚZPLN investigation examined the flight sequence, the aircraft's technical condition, and the meteorological environment. The investigation established that both pilots were qualified and held valid medical certificates. The aircraft was also found to be airworthy and maintained according to regulations. Meteorological conditions at the time were within limits for the flight, though the presence of a downdraft was a critical factor in the descent profile.
Findings
- The pilot maintained a level of confidence in the approach despite the increasing rate of descent.
- The aircraft's airspeed during the final stages of the approach fell below the minimum speeds specified in the L-23 Super Blaník flight manual.
- The pilot failed to react effectively to the aircraft's loss of altitude and the drop in airspeed.
- The primary cause of the accident was the aircraft striking the ground during the approach due to the airspeed falling below recommended limits.
- The impact with the ground caused skin wrinkling on the fuselage and center section, as well as damage to the landing gear attachments.
- One pilot was hospitalized for observation following the impact, while the other remained uninjured.