What happened
On December 19, 2010, an Airbus A319 arriving from Vienna was performing an approach to Cologne-Bonn Airport. During the turn onto the final approach, the flight crew began to notice an unusual odor in the cockpit. As the aircraft transitioned to the approach course, the odor intensified, leading to a significant decline in the physical and cognitive performance of both pilots.
Faced with symptoms of nausea and dizziness, the crew donned their oxygen masks and declared an emergency due to hypoxia-like symptoms. While the captain was able to maintain manual control of the aircraft, the co-pilot became too incapacitated to fulfill his cockpit duties. The aircraft landed safely on runway 14L, but the severity of the situation required medical intervention. Following the aircraft's arrival at the parking stand, both pilots were transported to a local hospital via ambulance. While the captain was able to return to flight duties after four days, the co-pilot remained unfit for duty for approximately six months.
The investigation
The BFU examined the flight data from the Quick Access Recorder (QAR) and the cockpit voice recorder (CVR). The investigation focused on identifying the source of the odor and the cause of the crew's physiological impairment. Investigators analyzed various technical systems, including the Environmental Control System (ECS), the rain repellent system, and potential leaks in the hydraulic or engine oil systems. The investigation also considered external factors, such as contamination from de-icing fluids used during the departure from Vienna, or the presence of atmospheric particulates.
Findings
Technical inspections of the Airbus A319 revealed no evidence of mechanical failure or system malfunctions. The investigation ruled out several potential sources of contamination, including carbon monoxide, engine oil leaks, hydraulic leaks, and the use of dry ice or insecticides. The investigators also found no evidence that the odor originated from the cabin or the passengers, as they remained unaffected throughout the event.
A massive odor development within the cockpit, the origin and distribution of which could not be determined, was the primary cause of the crew's health impairment. The physiological and psychological effects of these unidentified odors on the crew members acted as contributing factors to their diminished operational capacity.