Carbon Monoxide Symptoms with a Passenger On Board
After 40 minutes of a planned 2-hour flight in an ultralight with a passenger, you develop a dull headache, mild nausea, and unusual drowsiness. The passenger is quiet and says she feels “sleepy.” You are at 3,500 ft MSL, 18 nm from a suitable aerodrome and 35 minutes from your destination. Outside air temperature is 5°C, and you have been using cabin heat from the exhaust muff for the last 20 minutes. The engine is running smoothly. Visibility is 20 km, wind calm, and you have no carbon monoxide detector. You have no history of motion sickness, you ate a normal breakfast, and the cabin is closed with both occupants wearing warm clothing. Decide what to do.
1. What is the likely hazard, and what are the immediate actions?
Read the worked answer
Suspect carbon monoxide (CO) poisoning from the exhaust-heated cabin. Immediate actions: shut off cabin heat, open fresh-air vents or windows, reduce altitude if safe, and land at the nearest suitable aerodrome-18 nm away, not the destination 35 min away. Do not wait for symptoms to worsen. Keep the engine running only as needed. If able, declare an urgency or call the aerodrome. After landing, get both occupants out into fresh air and seek medical advice, especially if headache or drowsiness persists.
2. Why is continuing to the destination dangerous?
Read the worked answer
Continuing exposes both occupants to more CO. CO binds haemoglobin far more readily than oxygen, reducing oxygen delivery; early symptoms include headache, nausea, dizziness, and drowsiness, and judgment is impaired before the person realizes it. The passenger saying she is “sleepy” is a red flag, not a normal cruise event. At 3,500 ft there is also mild hypoxia, which adds to the effect. Without a detector, the absence of an alarm means nothing. A 35-min continued flight could leave the pilot incapacitated or the passenger unconscious.
3. What post-flight actions and preventive measures are appropriate?
Read the worked answer
Post-flight: both occupants should be medically evaluated; the aircraft should be inspected for exhaust leaks, a cracked muff, and faulty cabin-heat shrouds before further flight. Install a CO detector suitable for the cockpit, and use cabin heat only after a leak check. Do not fly the aircraft until the defect is fixed and signed off. Brief passengers on symptoms and on opening vents. Report the occurrence if required. Prevention is better than trying to diagnose CO in flight.