What happened
On 10 April 2018, a Vulcanair / Partenavia P68, registration F-HVEY, was conducting a ferry flight from Châteauroux-Déols to Pontoise Cormeilles-en-Vexin. While cruising at 2,000 feet, the pilot activated the aircraft's heating system and subsequently began experiencing nausea, headaches, and abdominal pain. Upon checking a carbon monoxide (CO) detection disc installed in the cockpit, the pilot observed that it had turned midnight blue, indicating a dangerous level of CO presence.
In response to the emergency, the pilot turned off the heating, opened the lateral windows to increase ventilation, and diverted to Orléans-Bocaquy Air Base. Following a safe landing, the pilot was transported to a regional hospital, where they received oxygen treatment and monitoring for two hours.
The investigation
The BEA investigation examined the aircraft's maintenance history, the cabin environment, and the engine exhaust configuration. The aircraft had recently undergone a 50-hour technical inspection, and the pilot had specifically requested a CO detection system for the flight.
Subsequent flight tests using electronic CO meters revealed that CO levels reached as high as 181 ppm during level flight. Investigators identified several discrepancies in the cabin, including obstructed air vents and a missing gasket on a duct in the left engine compartment. However, further testing determined that these specific maintenance issues were not the primary source of the contamination.
Testing eventually demonstrated that the interference in the airflow between the left engine exhaust flow and its potential conveyance into the cabin through the wing was the critical factor. On turbocharged models like this one, the exhaust outlet is offset in a way that aligns it with a flap bracket. This positioning creates a suction zone that draws exhaust gases into the wing structure and subsequently into the cabin.