What happened
On 30 March 2007, a Dornier 228-202, registration ZK-VIR, was conducting a positioning flight from Westport to Christchurch. During the climb to 10,000 feet, the pilot began experiencing significant dizziness and felt as though he might pass out. The check captain, who had taken control of the aircraft, soon developed similar symptoms, including blurred peripheral vision.
To mitigate the effects, the crew deactivated the air conditioning heating and utilized external ram air. The pilot also opened a side storm window to direct fresh air into the cockpit, which provided immediate relief to both crew members. Fearing air contamination, the crew issued a "pan pan" urgency call to Christchurch Air Traffic Control and requested a descent. The aircraft descended to 9,000 feet, and the crew maintained frequent communication with controllers to ensure they remained alert. The aircraft landed safely at Christchurch without further incident, and the crew subsequently sought medical evaluation.
The investigation
The investigation focused on identifying the source of the crew's physical symptoms and evaluating the aircraft's safety equipment. Investigators examined the air conditioning system, noting that the heating was supplied by engine bleed air. While no specific leak was found, the possibility of engine oil fumes being released when heated could not be ruled out. Toxicology tests on the pilots revealed slightly elevated levels of carbon monoxide, which, combined with the high cabin altitude, may have contributed to their impairment.
Additionally, the investigation revealed that the cockpit voice recorder (CVR) had failed to record the final 30 minutes of the flight, depriving investigators of critical audio evidence. The aircraft was also found to lack portable oxygen supplies for use during extended flights at moderate altitudes.
Findings
- The exact cause of the crew's partial incapacitation could not be definitively determined, though air contamination was the most likely factor given the relief provided by fresh air.
- The crew may have suffered from minor carbon monoxide poisoning, potentially caused by heated engine oil.
- The failure of the CVR prevented the collection of vital flight audio.
- The absence of portable oxygen limited the crew's ability to manage the physiological symptoms.
Safety action
Following the incident, the operator took several steps to enhance safety:
- The CVR was replaced with a modern digital recorder.
- An oxygen system was installed on ZK-VIR to provide accessible supply for both the crew and passengers.