Smoke entering the cabin of a dhc-8 during passenger boarding was determined to have come from a def...

Narrative:

While boarding for our first flight the APU gen had dropped off line. I contacted maintenance for the write-up. We cycled the circuit breaker to find that the generator would still not come on-line. I was issued an MEL for the APU gen and the flight was continued without further interruption until boarding the flight back.during the final boarding stage the first officer and I thought we smelled something coming through the duct work. As we mentioned it to one another; the flight attendant said she saw smoke entering the cockpit and realized that the cabin was filling with smoke as well. I turned off the recirc fan and bleed air which made an improvement (no more smoke entering the aircraft) but the smoke was still lingering. I quickly made a PA announcement for the passengers on board to exit the aircraft from the door through which they entered. After the announcement; I turned off the APU; external power switch; and the main; aux; and battery master switches.the first officer and I stood in the area outside of the lavatory door (where fresh air was present) until all passengers were off of the airplane. The flight attendant; first officer; and I attempted to find the source of the smoke however we found nothing. The three of us deplaned and entered into the breezeway where I contacted dispatch.a contract mechanic had the first officer attempt to start the APU but the starter would not engage. The mechanic said he thought it had something to do with the APU so I showed him where the APU access was located. While he was opening the hatch for it; I noticed more smoke/water vapor than usual coming out of the APU exhaust. The mechanic was sure at this point that the origin of the smoke was from the APU.after opening the access hatch he was able to quickly confirm his notion. After further discussion between the contract mechanic and maintenance control; they were able to determine the source of the smoke was the APU starter/generator. In light of this event it may be suitable for a mechanic to determine why the APU generator dropped off-line prior to the issuing of an MEL. I do not know if this contributed to the smoke incident but I understand that the smoke came from the APU starter/generator.

Original NASA ASRS Text

Title: Smoke entering the cabin of a DHC-8 during passenger boarding was determined to have come from a deferred APU generator/starter. The APU had been deactivated electrically but was still in use for air conditioning.

Narrative: While boarding for our first flight the APU GEN had dropped off line. I contacted Maintenance for the write-up. We cycled the Circuit Breaker to find that the generator would still not come on-line. I was issued an MEL for the APU GEN and the flight was continued without further interruption until boarding the flight back.During the final boarding stage the First Officer and I thought we smelled something coming through the duct work. As we mentioned it to one another; the Flight Attendant said she saw smoke entering the cockpit and realized that the cabin was filling with smoke as well. I turned off the RECIRC Fan and Bleed air which made an improvement (no more smoke entering the aircraft) but the smoke was still lingering. I quickly made a PA Announcement for the passengers on board to exit the aircraft from the door through which they entered. After the announcement; I turned off the APU; external power switch; and the main; aux; and battery master switches.The First Officer and I stood in the area outside of the lavatory door (where fresh air was present) until all passengers were off of the airplane. The Flight Attendant; First Officer; and I attempted to find the source of the smoke however we found nothing. The three of us deplaned and entered into the breezeway where I contacted Dispatch.A Contract Mechanic had the First Officer attempt to start the APU but the starter would not engage. The Mechanic said he thought it had something to do with the APU so I showed him where the APU access was located. While he was opening the hatch for it; I noticed more smoke/water vapor than usual coming out of the APU exhaust. The Mechanic was sure at this point that the origin of the smoke was from the APU.After opening the access hatch he was able to quickly confirm his notion. After further discussion between the Contract Mechanic and Maintenance Control; they were able to determine the source of the smoke was the APU starter/generator. In light of this event it may be suitable for a Mechanic to determine why the APU generator dropped off-line prior to the issuing of an MEL. I do not know if this contributed to the smoke incident but I understand that the smoke came from the APU starter/generator.

Data retrieved from NASA's ASRS site as of April 2012 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.

Attributes
ACN	914789
Time
Date	201010
Local Time Of Day	1201-1800
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Flight Conditions	IMC
Aircraft 1
Make Model Name	Dash 8-100
Operating Under FAR Part	Part 121
Flight Phase	Parked
Flight Plan	IFR
Component
Aircraft Component	APU Electrical
Person 1
Function	Captain
Qualification	Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Total 6200 Flight Crew Type 5100
Events
Anomaly	Aircraft Equipment Problem Less Severe Flight Deck / Cabin / Aircraft Event Smoke / Fire / Fumes / Odor

Smoke entering the cabin of a dhc-8 during passenger boarding was determined to have come from a deferred APU generator/starter. The APU had been deactivated electrically but was still in use for air conditioning.