What happened
On June 12, 1980, a pilot operating a Jodel D. 120 (HB-SVZ) was performing a flight from Lausanne to Zurich. Prior to the flight, the pilot had intended to fly to France and chose not to fully refuel the aircraft in Lausanne to take advantage of tax-free fuel availability on a future trip.
During the return leg of the flight, the pilot flew over the village of Chardonne at approximately 3,000 feet to notify his wife of his arrival. While executing a wide left turn toward Vevey, the engine began to sputter. Although activating the electric fuel pump briefly restored power, the engine failed completely a few seconds later. Faced with limited options near the Lavaux vineyards, the pilot bypassed a busy highway and the nearby lake to perform an emergency landing in a relatively flat vineyard. The aircraft struck the ground with its right wingtip and spun, resulting in the destruction of the aircraft and minor injuries to the pilot.
The investigation
Investigators examined the aircraft's fuel system and found no mechanical defects or leaks in the lines, carburetor, or tank. The investigation established that the fuel tank contained only 0.25 liters of fuel at the time of the accident, and the carburetor held approximately 5 ml.
Technical analysis of the fuel system revealed that the tank's filling neck was shaped in a way that prevented the pilot from performing a visual check of the fuel level or using a graduated dipstick. The pilot relied solely on an electric gauge that provided readings only in quarter-tank increments. Furthermore, calculations showed that the actual hourly fuel consumption during recent flights was significantly higher than the pilot's estimated average, contributing to the unexpected depletion of reserves.
Findings
- The engine failure was caused by fuel exhaustion.
- The pilot maintained an insufficient fuel reserve for the intended flight duration.
- The aircraft's fuel system design prevented an accurate verification of the remaining fuel quantity.
- The pilot's decision to fly with minimal reserves to avoid future refueling costs created an unacceptable level of risk.