Incident Overview
Shortly after departure, the flight crew observed smoke in both the cabin and the cockpit. The captain declared an emergency and executed a return landing at the departure airport. Upon landing, the captain directed an emergency evacuation of the aircraft.
Evacuation and Slide Failures
During the evacuation, several emergency slides failed to deploy. As a result of the slide failures, several passengers sustained injuries. Investigation determined that the slides failed due to improper packing, improper maintenance, and the use of improper parts.
Source of Smoke
The smoke observed by the crew originated from the #4 engine's #3 bearing labyrinth seal. The seal leaked as a consequence of a failure of the Engine Vibration Controller (EVC).