Incident Overview
After arriving at the gate in Chicago, fumes and smoke were observed in Zone C of the cabin. The cabin lighting subsequently failed, and the emergency lighting activated. Maintenance personnel found that the number 2 Auxiliary Power Unit (APU) had experienced an automatic shutdown due to a malfunction. The APU was placarded as inoperative, and the aircraft was returned to service.
Continuation of Flight
During the climb shortly after takeoff, smoke became noticeable in the cabin. The crew elected to return to the airport and land. After landing, the smoke had dissipated, and fire department personnel reported no indication of smoke or fire. Suspecting only an air conditioning problem, the crew decided to continue to the gate.
Evacuation
As the aircraft began taxiing, a flight attendant reported that the smoke was increasing. The captain stopped the aircraft and directed an evacuation. A crosswind prevented the proper deployment of the slides on the right side of the aircraft. During the evacuation, an elderly passenger using slide L-4 on the left side was seriously injured by others who came down the slide after him. Additionally, five passengers received minor injuries during the evacuation.
Investigation
Investigation revealed that the smoke was caused by oil from a failed APU bearing, which leaked into the air conditioning system.