Introduction
On 10 April 2017 at 09:30 local time, a Piper PA-28-181, registration HB-PFA, operated by Groupe de vol à moteur de Porrentruy, was parked at the fuel pump at Bressaucourt Aerodrome (LSQZ). The pilot, a French citizen born in 1981 holding a Private Pilot Licence (PPL(A)), had accumulated 167:08 hours total flight time, with 1:08 hours in the previous 90 days. He had 42:21 hours on type, with 1:08 hours in the last 90 days.
Sequence of Events
While the aircraft was static at the fuel pump, the pilot attempted to start the engine. He set the mixture to rich, engaged the booster pump, operated the manual primer three times, and advanced the throttle approximately one centimetre forward from the idle stop. Upon engaging the starter, the engine gave indications of starting but did not fire. For about 20 seconds, while continually engaging the starter, the pilot moved the throttle forward and backward, which delivered additional fuel into the carburettor via the accelerator pump. Again the engine did not start.
The pilot then stated he followed the required flooded engine procedure, but the engine still failed to ignite. Because another pilot needed to refuel, HB-PFA was moved to a different spot on the tarmac. To avoid draining the battery, the pilot decided to connect the aircraft to an external power source.
Subsequently, the pilot again attempted to start the engine by repeating the flooded engine procedure. White smoke began to emanate from the engine. Initially, the pilot was not concerned as the smoke was not dense. He then switched off all electrical consumers and turned the fuel selector to the "off" position. He left the aircraft to find a mechanic to address the starting issue. When they returned, thick smoke was billowing from the engine and flames were visible. The fire was extinguished using fire extinguishers.
The aircraft sustained heavy damage to the engine and cowls. The pilot and two passengers were not injured.
Conclusion
No technical malfunction was identified after the fire. The Swiss Transportation Safety Investigation Board (STSB) concluded that the fire in the engine occurred due to an excessive amount of flammable fuel. Based on Article 46, paragraph 1 of the Ordinance on Safety Investigations of Transport Incidents (OSITI), the STSB closed the investigation with this summary report.