What happened
On March 29, 2017, at approximately 13:30 UTC, a Discus bT motor glider was conducting a cross-country flight. After departing from St. Georgen - Ybbsfeld (LOLG) via a winch launch, the pilot utilized thermal activity to gain altitude and proceeded in a southwesterly direction.
In an attempt to return to the home airfield, the pilot decided to utilize the aircraft's retractable engine. To facilitate the engine start, the pilot configured the aircraft for a lower airspeed to allow the propeller to windmill. While the engine did start, it operated irregularly with significantly reduced power. Despite activating the electric fuel pump, no improvement in performance was observed.
Shortly after the engine was deployed, the aircraft entered a downdraft characterized by a high sink rate. Due to the combination of the engine's diminished performance and the increased drag from the deployed engine, the pilot could no longer reach the home airfield or the preferred landing field near Gresten. Consequently, the pilot was forced to perform an emergency landing on a nearby agricultural field.
During the landing, the pilot attempted to extend the landing gear at the last moment; however, it failed to lock into position and was forced back into the fuselage upon impact. The aircraft struck the uneven terrain of the field with significant force, causing the fuselage to break and the cockpit canopy to crack. The pilot sustained one serious injury to the back and was transported to a hospital via helicopter.
The investigation
The Austrian SUB examined the aircraft, the engine, and the flight conditions. A technical investigation of the Solo 2350 engine was conducted by the manufacturer. Investigators analyzed the wreckage, including the broken fuselage, the damaged elevator control linkage, and the cockpit components. The investigation also reviewed the pilot's flight experience, specifically regarding the operation of retractable engines, and evaluated the meteorological conditions, including wind speeds and terrain-induced air currents.
Findings
- The primary cause of the accident was a hard landing on the fuselage due to the inability to maintain altitude.
- The engine experienced irregular operation and reduced power due to technical deficiencies in the front cylinder, evidenced by significant oil leakage.
- The pilot had very limited experience operating the retractable engine, with only approximately seven minutes of engine runtime recorded.
- The pilot lacked sufficient altitude reserve to safely manage the engine deployment and the subsequent encounter with a high-sink-rate downdraft.
- High stress levels during the unplanned emergency landing contributed to the failure to properly secure the landing gear before impact.