What happened
On June 17, 2013, a DG-40 and registration HB-2202 was performing a self-launch from the grass runway at Grenchen Regional Airport. Shortly after the aircraft reached an altitude of approximately 30 meters, the engine began to lose power. The pilot attempted to maintain airspeed by adjusting the control stick and maneuvering to avoid trees, but the loss of power necessitated an immediate emergency landing. The glider descended into a nearby wheat field, where the right wing made contact with the vegetation, causing the aircraft to rotate 90 degrees on its vertical axis. The pilot escaped the heavily damaged aircraft without injury.
The investigation
Investigators examined the aircraft's maintenance history and the mechanical state of the engine. It was noted that the pilot had performed several self-directed maintenance tasks, some of which were not included in the approved maintenance program. The investigation also revealed that the aircraft's flight and maintenance manuals had not been updated with the latest manufacturer revisions. Technical inspections of the engine revealed significant damage to the pistons and cylinders, as well as corrosion on the engine mount.
Findings
- The primary cause of the accident was the engine failure during the initial climb.
- A defective vacuum fuel pump caused a lean fuel-air mixture, leading to the engine's power loss.
- The failure to replace the vacuum fuel pump according to the manufacturer's recommended 300-hour or six-year interval contributed to the engine's degraded state.
- Maintenance practices were inconsistent with manufacturer and authority recommendations, including the use of unapproved maintenance procedures and outdated documentation.
- The engine's fuel system redundancy failed because the faulty vacuum pump prevented fuel from reaching the carburetors despite the functional electric pump.