What happened
On August 6, 2018, at approximately 16:15 LMT, a DG-1000 glider, registration D-KSOE, was performing a training takeoff at the Zielona Góra – Przylep (EPZP) aerodrome. The glider was being towed by a JAK-12 aircraft. Shortly after rotating at an altitude of 3–4 meters, the glider lost its directional heading. The pilot attempted to correct this using ailerons, which caused the glider to oscillate side-to-side, subsequently causing the towline to slacken.
To tension the line, the pilot deployed the airbrakes. However, the pilot failed to retract the airbrakes once the line was taut. Due to the high mass and large wingspan of the glider, the aircraft could not climb while the airbrakes were extended, maintaining an altitude of only 5–10 meters. Seeing that the aircraft could not clear the upcoming treeline, the tow plane pilot decided to release the glider. The glider pilot did not release the towline from the glider side, leaving it trailing behind.
Following the release, the pilot attempted a 180-degree turn to return to the aerodrome. This maneuver was performed at an extremely low altitude, with the wingtip passing within 1.5 to 3 meters of the ground. The pilot eventually leveled the aircraft at an altitude of 3–5 meters, but the glider struck the aerodrome perimeter fence during the landing roll. The impact caused severe damage to both the left and right wings of the DG-1000.
The investigation
The PKBWL examined the flight sequence, the pilot's actions, and the technical state of the aircraft. The investigation confirmed that the pilot held all necessary licenses and the glider was properly documented and insured. The investigators analyzed the aerodynamic consequences of using airbrakes during a tow and evaluated the safety of the landing decision made at low altitude.
Findings
- The primary cause of the initial instability was the oscillation of the glider caused by the pilot's use of ailerons to correct direction, which led to the slackening of the towline.
- The pilot failed to retract the airbrakes after the line was tensioned, preventing the glider from climbing.
- The pilot made a critical error by attempting a 180-degree turn at an altitude of approximately 10 meters; a landing on a straight path or a shallower turn toward the adjacent stubble field would have been safer.
- The pilot failed to release the towline from the glider side after the aircraft released it from the plane, creating a hazard.
- The flight director did not use radio communication to instruct the pilot to close the airbrakes during the unstable takeoff phase.