Accident Overview
On 17 June 2013, at approximately 12:16 local time, a DG-400 self-launching glider, registered as HB-2202, experienced an engine failure shortly after departing from the regional airfield of Grenchen, Switzerland. The aircraft was forced to land in a wheat field about 1 km southwest of the runway. The sole pilot was uninjured, but the glider sustained heavy damage. Minor ground damage occurred.
Flight History and Pilot Background
The pilot, a Swiss citizen born in 1961, held a glider license issued in 2003 and had accumulated 1,208 total flight hours, with 1,121 hours on the accident type. He lived abroad and flew the glider only during the gliding season. In 2011 and 2012, he flew 13 and 10 flights respectively. The last flight prior to the accident season was on 23 June 2012. In 2013, the pilot flew four times before the accident, with engine problems noted on three of those flights.
Accident Sequence
On the day of the accident, the pilot prepared the glider as usual, performed pre-flight checks, and filled the fuel tank with 20 liters of autogas mixture. After a backtrack on grass runway 25, he conducted a run-up check and reported that everything functioned normally. Takeoff began at 12:15. The pilot stated that the climb was normal until reaching about 30 meters above ground, when engine power began to decrease, described as similar to turning off the fuel, not abrupt. He immediately lowered the nose to gain speed and turned left to avoid trees. The glider made an emergency landing in a wheat field, during which the right wing contacted crops, causing the aircraft to yaw 90 degrees to the right. The pilot exited the damaged glider unaided.
Meteorological Conditions
Weather at the time was sunny with light and variable winds at 2 knots, visibility 20 km, and a temperature of 27°C. The pressure setting QNH was 1014 hPa. The general weather pattern placed Switzerland in tropical air ahead of a trough over Western Europe.
Aircraft and Maintenance Information
The DG-400 (HB-2202) was a single-seat high-performance self-launching glider manufactured in 1991. Its engine was a Rotax 505 A two-cylinder two-stroke with a Mikuni carburetor and Ducati electronic dual ignition. The airframe had 2,164:12 hours total time since new (TSN), while the engine had 129:24 hours TSN. The flight manual on board was not current, lacking revisions since November 1992; the latest manufacturer revision was from June 2004. The maintenance manual also was outdated, last updated October 1996.
In the year before the accident, several maintenance actions were performed. On 3 July 2012, a BAZL inspection noted that fuel lines needed replacement per the maintenance manual. On 18 July 2012, a certified maintenance organization replaced the fuel lines partially with hoses used in other aircraft. The pilot was informed. A subsequent ground test showed only 3,000 rpm; a missing restrictor in the fuel return line was then installed. Another test showed satisfactory rpm, but during a test flight later that day, the engine rpm dropped halfway down the runway, causing the pilot to abort. He then ended the season and stored the glider until May 2013.
On 27 May 2013, the pilot returned and performed the annual inspection. He contacted the same maintenance organization to overhaul the carburetor. On 7 June 2013, the carburetor was removed, cleaned, and diaphragms replaced. A test run was reported as satisfactory. The pilot assisted in the work and performed the functional test himself. During a subsequent test flight, the engine ran well to 1,000 m above mean sea level, then dropped 300–400 rpm, but the pilot continued to 1,400 m and shut down. The flight manual entry noted "Fuel hoses replaced, carburetor overhauled. Test flight OK."
On 8 June 2013, another test flight may have occurred, but no further details are provided in the source.
Probable Cause
The accident was caused by an emergency landing of the self-launching glider due to an engine failure shortly after takeoff. The poor condition of the engine and its accessories contributed to the accident.