What happened
On June 16, 2017, a Piper PA-28-1181 (registration HB-PAT) was engaged in a training flight departing from Gruyère Aerodrome (LSGT). The pilot, conducting a private flight under Visual Flight Rules (VFR), initially noted that approximately 17 gallons of fuel were distributed between the left and right wing tanks. Due to ongoing glider activity at the airfield, the pilot elected to perform slow flight exercises and spirals near Romont, followed by a scenic flight along Lake Geneva via Vevey and Montreux, before returning to Epagny for circuit work.
During the flight, the engine was being supplied by the right wing tank. After completing two landings on runway 35, the pilot attempted a third takeoff. During this final departure, the aircraft experienced a sudden loss of engine power at a low altitude. To avoid the nearby village of Broc, the pilot immediately turned to the left. Despite attempting to switch the fuel source to the left tank, the engine failed to recover, and the aircraft subsequently landed in a wheat field. While the pilot sustained slight injuries, the aircraft remained undamaged, though the landing caused minor damage to nearby crops.
The investigation
The investigation focused on the cause of the engine power loss during the takeoff phase. Investigators examined the fuel system and the state of the fuel tanks following the incident. Upon inspection of the aircraft on the ground, it was determined that the right wing tank was completely empty.