Date: 201205
Local time of day: 0601-1200
Location: ZZZ.Airport, US
Flight conditions: VMC
Weather elements / visibility: 10
Light: Daylight
Aircraft: Dash 8-100
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Descent
Airspace: Class C ZZZ
ATC / advisory: TRACON ZZZ
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Anomaly: Flight Deck / Cabin / Aircraft Event Smoke / Fire / Fumes / Odor
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Landed in Emergency Condition; General Evacuated; General Maintenance Action
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: While on approach the First Officer informed me that he smelled smoke. Within seconds we both saw smoke rising from underneath the First Officer's seat and instrument panel. The First Officer declared an emergency with ATC and gave fuel and souls. We then preceded with the emergency action items on the smoke from an unknown source checklist. We took the masks off of the hooks but I asked that we not use them as we were close to the field and I wanted clear communication with the First Officer and the Flight Attendant. The First Officer turned off the recirc fan and bleeds. He also turned on the emergency lights. He then notified the Flight Attendant that we would be doing an emergency landing at our destination with an evacuation on the runway. No plan for brace or evac out the side exits was made. The Flight Attendant was told to evacuate via the forward air stair door only. While he was talking to the Flight Attendant; I requested immediate landing on the runway; asked that ATC contact company ops and began our descent from 6;000 FT. I completed the approach checklist and the First Officer announced that the smoke from an unknown source checklist was complete. We landed on the runway; cleared the runway onto a taxiway; shut down the aircraft; and started the evacuation through the forward air stair door. The First Officer left the cockpit to help with the evac. After the last passenger was out I asked the Flight Attendant to go to the passengers and get a head count. I then went to the back of the aircraft to verify all seats were empty. The Fire Fighters began to enter the aircraft and I informed them that the aircraft was clear and electrically dead except for the emergency lights which were still on. At this point I asked the First Officer to go get another head count of the passengers while I talked to ARFF personnel. I met with the Airport Operation's Supervisor as well as our operations Supervisor and discussed how to go about moving the aircraft and how to return personal possessions to the passengers. My crew and I remained with the aircraft for the rest of the day as Maintenance tried to determine the cause of the smoke.At this time I am not aware of the specific source of the smoke. During my last conversation with Maintenance I was told that the engine bleed air and the ACM were being considered as possible sources.




Synopsis: After sensing smoke emanating from the vicinity of the First Officer's station as they descended toward their destination; a Dash 8 flight crew declared an emergency; landed and evacuated the aircraft after clearing the runway.