What happened
On June 12, 2020, a Blackshape BS100 Prime, registration OM-M619, was performing a flight from Kříženec (LKKC) to Jindřichův Hradec (LKJH) when the pilot experienced a sudden loss of engine power. During the return leg of the flight, the pilot noticed highly fluctuating fuel indications on the digital display, with levels swinging between 3 and 15 liters. Shortly before reaching the threshold of runway 07 at LKJH, the engine began to run irregularly before failing completely.
Realizing the aircraft could not reach the runway, the pilot executed an emergency landing in a field containing tall crops. The aircraft struck the ground, bounced, and spun approximately 120 degrees before coming to a complete stop. The pilot sustained light injuries, while the passenger was uninjured. The aircraft sustained extensive damage, including a broken propeller blade, a punctured cockpit canopy, and structural damage to the wing and landing gear.
The investigation
The ÚZPLN investigation examined the aircraft's fuel system, flight logs, and maintenance records. Investigators found that the fuel selector valve was in the "OFF" position upon inspection. A physical examination of the fuel tanks revealed that the vent lines in the center section of the wing were mechanically broken, leading to a leak in the vent system.
Furthermore, the investigation found that the pilot had been flying with known issues, including a smell of fuel in the cockpit and a malfunctioning fuel gauge in the right wing, which had been occurring for approximately three months. These findings had not been recorded in the aircraft's technical logbook. The investigation also noted that the pilot was flying without a valid LAA(A) license at the time of the accident.
Findings
- The primary cause of the accident was fuel exhaustion caused by the pilot's inaccurate assessment of the actual fuel remaining versus the actual hourly fuel consumption.
- The pilot's pre-flight calculations were based on an estimated fuel consumption rate that was lower than the actual consumption experienced during the day's flights.
- Contributing factors included the incorrect configuration of the Dynon SkyView system, which was set to a lower consumption rate than reality.
- A malfunctioning fuel level indicator in the right wing prevented accurate monitoring of fuel levels.
- Leaks in the fuel tank vent lines likely contributed to fuel loss.
- The failure to document known fuel system irregularities, such as the smell of fuel and gauge malfunctions, in the technical logbook prevented timely corrective action.