What happened
On October 24, 2016, an Avro 146-RJ10 and registration HB-IYR, operated by Swiss Global Air Lines, was performing a scheduled flight from Birmingham to Zurich. During the initial taxi in Birmingham, the flight crew and cabin chief noticed a distinct smell of oil in the cockpit. To mitigate the odor, the crew decided to shut down the Auxiliary Power Unit (APU) and proceed with the takeoff using only engine bleed air for ventilation.
During the descent toward Zurich, the crew deactivated the aircraft's anti-icing system at approximately flight level 8000. Shortly thereafter, a heavy oil odor returned to the cockpit, prompting the crew to don their oxygen masks. The pilots issued a 'Pan Pan' urgency call to air traffic control, requesting priority for their approach to Zurich. The aircraft landed safely on runway 28 at 19:36 UTC. Upon arrival, ground services conducted air quality testing in the cockpit, and medical checks of the crew's blood oxygen and carbon dioxide levels showed no abnormalities.
The investigation
Maintenance teams performed extensive inspections of the four engines and the APU, including borescope examinations. While a hydraulic oil leak was identified and repaired, it was not determined to be the source of the odor. However, subsequent testing with an Aero Tracer device revealed that oil particles were present in the air specifically when bleed air from engine number 2 was utilized.
This incident followed two similar occurrences involving the same aircraft earlier in October 2016, where crews reported unpleasant odors. Because the operator was in the process of retiring the Avro 146 fleet, the decision was made to replace engine number 2 rather than perform a more invasive teardown of the component.