What happened
On December 5, 2005, an AVRO 146-RJ100, registration HB-IXQ, operated by Swiss European Air Lines, departed Zurich Airport for a scheduled flight to Brussels. Shortly after takeoff, while the aircraft was climbing through FL100, the pilot noticed smoke appearing near the left side console. The smoke quickly spread, becoming visible to the co-pilot and the cabin crew.
In response to the smoke, the flight crew donned their oxygen masks and declared an emergency at 09:02 UTC, requesting an immediate return to Zurich. During the approach to runway 14, the smoke began to dissipate, but the captain experienced significant difficulty communicating with the co-pilot and air traffic control due to a continuous oxygen flow through his mask. Despite attempts to adjust the equipment, the flow could not be stopped, eventually requiring the co-pilot to take over radio communications. The aircraft landed safely at 09:16 UTC, and passengers were disembarked via the terminal.
The investigation
The Swiss Transportation Safety Investigation Board (SUST) examined the technical components of the engine and the cockpit emergency equipment. The investigation focused on the source of the smoke and the functionality of the crew's oxygen masks. Investigators also reviewed maintenance records, noting that a temperature control valve had been replaced the previous night following a previous warning regarding engine air valves.
Findings
- The smoke was caused by oil leaking from a defective seal located near bearings No. 1 and No. 2 of engine No. 2. As the oil entered the air conditioning system, it evaporated, creating the smoke observed in the cockpit and cabin.
- The crew's decision-making and emergency procedures were appropriate and timely.
- The captain's communication difficulties were exacerbated by the continuous oxygen flow. While the mask itself was not defective, investigators found coffee residue on the membrane, which can impede proper function. Additionally, the position of the mask's emergency pressure knob was a factor in the continuous flow.
- The oxygen mask service life for the captain's side had expired 10 months prior to the incident.