History of the Flight
On 14 September 2020, a GROB G115, registered F-GGOB, operated by Aero Pyrénées, departed Troyes airport for a cross-country flight to Amboise aerodrome. While cruising at 3,000 ft, the pilot noticed a smell of burning, which he attributed to the ventilation system. He decided to abort the flight and diverted to Aubigny-sur-Nère aerodrome, where he landed without incident.
After engine shutdown, the pilot detected no unusual smell. He performed a visual inspection and the start-up checklist, both revealing no anomalies. Concluding it was a false alert, he decided to resume the flight and taxied to the refuelling station. Upon reaching the fuel pump, he shut down the engine.
While the pilot and passenger remained on board, the pilot observed flames and white smoke emanating from the engine compartment. He executed the fire emergency procedure, evacuated the aircraft with the passenger, and called emergency services. The fire was extinguished before it spread beyond the firewall.
Examination Findings
The aircraft was stored in a hangar at Aubigny-sur-Nère aerodrome and examined by the BEA. Damage was confined to the engine compartment. Cowlings, the engine, and the propeller spinner were covered in soot. Several components showed deterioration typical of excessive heat exposure, extending across the front and upper parts of the engine up to the firewall.
Further examination indicated that the flames and white smoke originated from the front of the engine. The only anomalies in the oil system were found in the breather pipe and the pressure sensor. Laboratory analyses of the pressure sensor and engine cowling parts confirmed the presence of engine oil in combustion residues. The fuel system showed no damage. It appeared that the combustible material contributing to the fire was engine oil, but the exact cause of the failure could not be determined.
Conclusions
The pilot likely detected an oil leak onto hot engine parts during flight, producing the burning smell. By aborting the flight and landing, he probably prevented a more critical situation. However, he did not perform a troubleshooting procedure on the ground, relying solely on visual inspection and the start-up checklist, leading him to wrongly conclude it was a false alert. The fire, caused by escaping engine oil, occurred while the aircraft was stationary at the refuelling area. The investigation was unable to determine the specific failure that allowed the oil to escape.