Event Overview
On 19 December 2010, an Airbus A319-132 aircraft was on approach to Cologne-Bonn Airport, originating from Vienna, Austria. While turning onto the base leg, both pilots detected an unusual odor. Shortly thereafter, during the turn onto final approach, they experienced impairment of their physical and cognitive performance. They donned their oxygen masks and declared a mayday.
Cockpit Crew Response
The captain was able to continue flying the aircraft, while the copilot reported feeling unable to fully perform his cockpit duties. After landing and reaching the parking position, both pilots sought medical treatment. The captain was medically cleared to resume flight duties after four days, but the copilot was deemed unfit for flight duty until 10 July 2011.
Technical Investigation
A thorough technical examination of the aircraft found no evidence of any technical malfunction. The aircraft's climate control system and the rain repellent system were inspected, but no defects were discovered that could explain the odor or the crew's symptoms. The investigation also reviewed maintenance records and air sample tests, but no specific contaminant was identified.
Meteorological and Operational Context
The weather at the time was not considered a contributing factor. The aircraft had been de-iced prior to departure, and no anomalies were reported during the flight until the approach phase. The flight crew had adequate rest and were experienced.
Human Performance Aspects
The flight crew's medical and pathological examination revealed no pre-existing conditions that would have contributed to the incident. The investigation considered the possibility of an "aerotoxic syndrome" but could not confirm it due to the lack of identification of a specific toxic substance. The crew's response, including the use of oxygen masks and declaration of an emergency, was in accordance with standard procedures.
Conclusion
The investigation concluded that the cause of the serious incident could not be determined. No technical or procedural failures were identified that would explain the odor and the subsequent impairment of the flight crew. The report did not assign a probable cause.