History of the Flight
On 6 December 2014, a Robin DR400-120, registered F-GOVA, departed from Cambrai for a night VFR instruction flight. The pilot in the left seat was accompanied by a second pilot in the rear and an instructor in the right seat. The purpose was to obtain a night rating. At approximately 500 ft altitude, the pilot reported feeling unwell and transferred control to the instructor. Simultaneously, the instructor and the rear pilot also began feeling unwell. Despite difficulty controlling his limbs, the instructor took control while the front pilot opened the canopy one-third to ventilate the cockpit. The instructor executed a steeply banked (estimated 45°) right U-turn to land on the reciprocal runway as quickly as possible. Upon touchdown, the instructor described a state of lethargy bordering on sleepiness but managed to control the aircraft and stop on the runway without damage.
Additional Information
The night was clear with some mist, visibility 4,400 m, and outside temperature +3°C. During pre-flight inspection, the carbon monoxide (CO) detection patch appeared normal to the instructor, though after engine start he noted it seemed darker than usual under his flashlight. He checked with a mobile phone light and still perceived it as yellow/orange but darker. Another pilot thought the patch was dark green. The instructor acknowledged uncertainty and briefed that if any physiological effects occurred, they would open the canopy. During take-off, the instructor turned off heating for demisting and opened the front and rear air nozzles. He reported wobbly legs, nausea, and dizziness. After landing, all three occupants displayed symptoms of carbon monoxide poisoning and noted a strong smell of exhaust fumes likened to heating, which had not been perceptible in flight. On the ground, the CO detector patch was black. The aircraft's previous flight 30 minutes earlier reported no issues. Emergency services provided oxygen and transported the pilots to hospital, where blood tests showed one occupant had 18% CO, the second 12%, and the third 10%.
Engine and Engine Compartment Examinations
Post-occurrence examination of the engine compartment revealed:
- A leak at the ceramic seals of the exhaust pipe due to wear of the gland packing on cylinders 2 and 4, allowing exhaust gases into the engine compartment.
- Weld beads indicating repairs to numerous cracks in the manifold.
- Wear on the peripheral seal of the shut-off flap of the heating control box.
- The flexible hose connection supplying hot air from the heat exchanger housing to the heating control box had been switched with the connection supplying hot air to the carburettor air inlet.
Conclusions
The incapacitation of the three persons onboard was the result of inhaling carbon monoxide. The instructor's doubt about the CO detection patch colour led to a pre-take-off briefing about the risk, enabling a swift reaction after poisoning symptoms emerged. Contributing factors included the switching of two flexible hose connections on the exhaust manifold and progressive leakage due to a worn ceramic gasket/gland assembly on cylinders 2 and 4.