Event Description
A Boeing 717 was on final approach when the display units (DUs) in the cockpit blanked and the cockpit darkened. Smoke was smelled in both the cockpit and the cabin. In the cabin, the emergency light illuminated for a few minutes, then all lights extinguished, leaving the cabin dark. The landing gear was lowered, and when the flaps were positioned to 40 degrees, a landing gear aural warning commenced and continued until power was removed after landing.
Crew Actions
The captain reported that when the event began, he directed his vision outside the cockpit and kept it there until after landing. The co-pilot also reported directing his vision outside the cockpit during the final 20 seconds of approach. Neither pilot used the standby instruments or a flashlight to check instruments.
Emergency Evacuation
After clearing the runway and stopping, the captain commanded an emergency evacuation. In interviews, flight attendants reported that during the evacuation, they did not check conditions outside their doors before opening them. Cabin emergency lighting was not activated by the flight attendants, and the flight attendant at the tail cone station was unable to deploy her slide.
Examination Findings
Examination of the airplane revealed that the left power control distribution unit (PCDU) had failed. The left DC bus was also lost, and the ability to power the left DC bus from other sources was lost. The failure of the PCDU was not instantaneous; it attempted to recycle several times. Each time the PCDU recycled, it reset the display of new data on the remaining display units, causing an extended blank display followed by eventual reset of data. The pre-programmed response to the loss of the left DC bus was the loss of two display units, one on each side of the cockpit.