What happened
On May 6, 2015, a Bombardier DHC-8-402Q operating a scheduled flight from Vienna-Schwechat (LOWW) to Innsbruck (LOWI) experienced a serious in-flight disturbance. Approximately two minutes after takeoff, as the pilots engaged the bleed air switches for both engines, smoke began to appear in the passenger cabin and subsequently in the cockpit.
The flight crew immediately responded by donning oxygen masks and initiating the "Fire/Smoke Flight Deck" checklist. The pilots decided to return to Vienna-Schwechat for an emergency landing. During the descent, the crew worked through the "Fire/Smoke-Unknown Source" checklist, which helped them identify that the smoke was linked to the bleed air from the right engine.
The aircraft landed safely at LOWW. Although emergency services were positioned near the runway, the crew elected to taxi to a parking position rather than perform an immediate runway evacuation. All 43 passengers and 5 crew members disembarked without injury.
The investigation
The Austrian SUB examined the aircraft's engines, specifically the right-hand engine, and analyzed the environmental control system (ECS). The investigation focused on the source of the smoke, the integrity of the engine components, and the crew's response to the emergency. Investigators also reviewed the maintenance of the engine oil and the cleanliness of the air conditioning filters.
Findings
- The primary cause of the smoke was a damaged seal on the #2.5 bearing.
- This damage resulted in a loss of pressure sealing, allowing engine oil to leak into the bleed air system via the inter-compressor case (ICC) at the P 2.7 air extraction point.
- The contaminated oil then entered the Environmental Control System (ECS), spreading smoke throughout the cabin and cockpit.
- During the emergency, there were inconsistencies in how the cabin crew demonstrated the brace position to passengers.
- The cabin crew did not remove potentially hazardous items (such as scarves or pins) from their clothing as part of their self-protection procedures.