What happened
On October 26, 2017, a private pilot was conducting a local sightseeing flight in a Robin 155CDI, registration HB-KLM. The flight originated from Zweisimann Airport (LSTZ) and followed a route passing over Tsanfleuron toward Spiez via the Fribourg (FRI) beacon. While flying in the Schwarzsee region at an altitude of approximately 7,500 ft AMSL, the engine began to sputter, resulting in a loss of power.
Recognizing the developing situation, the pilot decided to return to Zweisimann Airport, maintaining Boltigen as a potential emergency landing site on a large field. The pilot successfully landed on runway 17 at Zweisimann without further incident, though the engine stopped running at the end of the runway. Upon refueling the aircraft, the pilot discovered that the fuel tanks were completely empty.
Findings
- The pilot was aware that the fuel gauge on the aircraft was unreliable and did not always provide an accurate reading of the remaining fuel.
- At the start of the flight, the fuel gauge indicated a 75% fuel level.
- The lack of adequate monitoring of fuel reserves despite the known malfunction of the fuel gauge led to the engine power loss.