Event Description
On 2 August 2024 at 18:06 UTC, a HPH Sailplanes TwinShark 304 TS glider, registration D-KDRG, was returning to Rieti Airport during a gliding competition. The pilot, with 2049 hours total flight experience (670 on type), and a passenger were on board. According to the pilot, the competition had been long and demanding, lasting approximately 6 hours 49 minutes, with a delayed start. Thermals weakened near the end of the flight, but the pilot believed he could complete the planned flight.
Approaching Rieti Airport, the pilot realized he was at an altitude of about 200 meters (600 feet) and trusted he would encounter a thermal to complete the flight. At around 100 meters (300 feet), he decided to extend and start the engine. The engine extended normally but failed to start. The pilot later stated he believed he omitted operating the manual fuel primer as per the flight manual. The increased drag from the extended engine increased the descent rate, forcing the pilot to execute an off-field landing approximately 2 nautical miles northeast of the airport.
The pilot selected a field that appeared flat but was traversed by furrows. After landing, the glider rolled about 40 meters before impacting a furrow approximately 40 centimeters deep and 1 meter long. The impact occurred at the fuselage near the passenger position. The glider continued for another 50 meters before stopping. Both occupants evacuated; the passenger sustained injuries classified as serious under aviation regulations, while the pilot was uninjured.
Investigation Findings
Post-accident examination confirmed the aircraft was airworthy and properly maintained before the flight. The pilot held valid medical and license documents. Meteorological conditions at Rieti Airport at the time were good visibility, no precipitation, wind from 170 degrees at 7 knots (METAR: LIQN 021750Z 17007KT CAVOK 30/14 Q1010).
Photographic evidence showed substantial damage to the lower fuselage, structural ruptures and deformations, a broken tail section at the wing trailing edge, and damage to vertical and horizontal stabilizers and control surfaces. Ground contact marks extended approximately 80 meters, and the glider came to rest on its left wing.
During a subsequent test, the engine started successfully both after the event and during a functional test days later, demonstrating perfect efficiency. The pilot had performed a successful engine extension and start test after the accident.
The pilot reported that the engine start procedure was not executed correctly: he omitted operating the manual fuel primer. The flight manual for the TwinShark 304 TS includes an emergency procedure for engine failure at low altitude recommending retraction (even partial) to improve gliding performance.
Probable Cause
The incident is attributable to an incorrect in-flight engine start procedure to regain or maintain altitude. The extended but non-functioning engine worsened glide performance by increasing drag. This forced the pilot to an off-field landing on flat but furrowed terrain. One furrow caused damage to the glider and serious injury to the passenger during the ground deceleration run. Contributing factors included fatigue from the long flight and the pilot's strong determination to complete the competition without engine assistance.