What happened
On August 14, 2011, a DG-40 and glider, registration OK-2154, was engaged in a thermal soaring flight near Benešov. After being towed from Benešov Airport (LKBE) and releasing from the tow plane at approximately 600 meters AGL, the pilot began searching for thermal currents in the area south of the airfield.
While flying in a light thermal updraft with flaps set to +6°, the pilot noticed the aircraft began to pitch forward and transitioned into a steep, uncontrolled descent. The change in flight characteristics occurred without warning. As the aircraft's descent rate increased, the pilot attempted to recover by repeatedly pulling back on the control stick. However, the descent rate continued to accelerate.
At an altitude of approximately 400 meters AGL and a speed of 150–160 km/h, the pilot jettisoned the cockpit canopy and exited the aircraft. The glider struck an unharvested cornfield approximately 250 meters from residential buildings, landing on its back at an angle of 10–15°. The pilot successfully deployed a parachute and landed approximately 500 meters from the aircraft's impact site. There were no injuries to the pilot.
The investigation
The ÚZPLN investigation relied on pilot testimonies, wreckage examination, and a technical inspection of the aircraft. The investigation included a review of the DG-400 flight manual and consultations with pilots experienced in this specific glider type. Technical inspections confirmed that the aircraft was airworthy and that the control surfaces and linkages were fully functional at the time of the accident. The investigation also attempted to retrieve flight data from the onboard LX 7007 PRO IGC and Universal Sensor Box-D, but the recording media were found to be destroyed by the impact.
Findings
- The glider entered a stall, most likely at a low airspeed.
- The pilot used recovery techniques that contradicted the manufacturer's flight manual, which advises slightly pushing the control stick forward during a low-speed stall rather than pulling back.
- The pilot had limited experience specifically with the DG-400 model.