The Austrian Federal Safety Investigation Authority (SUB) published their final report into the investigation of a serious cabin smoke incident involving a DHC-8-400.
On May 6, 2015, a de Havilland Canada DHC-8-402Q of Austrian Airlines operated on flight OS905 from Vienna-Schwechat International Airport to Innsbruck, Austria. Shortly after take-off from Vienna Airport, when the pilot operated the switches for the bleed air from both engines (bleed 1 and 2), there was a presence of smoke. First smoke appeared in the cabin and shortly thereafter in the cockpit.
When the cabin crew noticed fumes in the passenger cabin, they broke off the after-takeoff announcement and immediately informed the two pilots. At the same time, the smoke alarm activated in the toilet, which subsequently could not be muted by the cabin crew. The first officer, who was Pilot Flying, ordered the donning of the oxygen masks and started the processing of the “Fire / Smoke Flight Deck” checklist. Both pilots decided shortly thereafter to turn back to the Vienna Airport.
The first officer stopped the climb at about 5000 feet and started to turn back to the airport. An emergency was not declared. After executing the “Fire / Smoke – Flight Deck” checklist there was no improvement in the situation. The “Fire / Smoke-Cabin” checklist also brought no change. Then after executing the “Fire / Smoke-Unknown Source” checklist there was an improvement in the situation. The pilot determined that the smoke apparently was connected with the bleed air of the right hand engine. By this time the aircraft was about 12 nautical miles from the threshold of runway 34 of the Vienna Airport.
The landing approach to runway 34 was flown using the Instrument Landing System. The landing was normal, except for the still existing smoke in the cabin. After landing the aircraft was stopped on runway 34. The rescuers were able to examine the aircraft visually from the outside.
Apart from slight smoke on the inside of the right engine no visible damage was evident. This was communicated by radio contact the two pilots, whereupon they decided not to carry out an evacuation on the runway 34, but to taxi the aircraft to a designated parking position and to disembark the passengers there in the normal way. Having arrived at this parking position, the access doors of the aircraft were immediately opened to escape the smoke and let fresh air into the cabin of the aircraft.
The serious incident has been caused by damage in a seal of bearing #2.5. This damage resulted in the loss of bleed air sealing of the bearing # 2.5 and, consequently, to the fact that oil entered through the bleed air connector P 2.7 in the Inter-Compressor Case (ICC) into the Environmental Control System (ECS).