Narrative:

Preparing to depart; running late due to weather and ATC delays; the aircraft got toasty quickly as ramp had pulled the air without giving us a signal; per usual; in non-compliance with procedure. We started the APU; waited one minute; and put the right bleed on high cold to try to stop the rising cabin temperature. Immediately there was a faint; but noticeable smell of burnt oil or something in the cockpit. First officer (first officer) asked if I smelled it and as I responded I saw smoke drifting by us outside my window; and then smoke in the cockpit almost immediately after.I told first officer we needed to get the people off now; looked back to tell the a flight attendant (flight attendant) to deplane everyone through the main entry/jetway; and saw smoke filling the back of the aircraft. We turned off the pack and bleed and before we could kill the APU it died; leaving us with no AC power; and just the battery. This all transpired in just a couple of seconds. About that time the aft smoke alarm sounded; followed by the forward alarm. No fire light indication was present. I called ground on VHF1; notified them of the situation and asked them to roll the fire trucks in case there was a fire.I then tuned operations into VHF1; notified operations; and got up to see what I could do to help in the cabin. The evacuation was going well there; so I asked first officer to take care of things in the aircraft while I go see what the status of the fire trucks was; and what exterior situation was. No passengers were showing signs of effects from smoke. They all left their belongings and moved quickly off of the aircraft. Fire and rescue personnel met me in the jetway and told me that there was no fire; but a lot of oil leaking from the tail. I confirmed that there was a large puddle of oil below the APU; with more dripping fairly quickly onto the ground.maintenance came up and confirmed that the APU oil had leaked; causing the smoke; and said he would MEL the APU and get us on our way. I had him open the APU door and inspect for fire damage while first officer and I discussed whether or not we liked the plan. Ground operations asked if I'd like another aircraft; I said I would; and we were moved to another aircraft. Dispatch and chief pilot on call were contacted and briefed on all of the above. A log book entry was made.the fas were removed and replaced. First officer and I agreed that we were okay; swapped aircrafts and continued to our destination. The fas and first officer all did an excellent job; and were very professional and calm.

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Original NASA ASRS Text

Title: A B737 Captain reported after boarding and staring the APU; APU leaked oil into the air conditioning system resulting in cabin smoke and an evacuation at the gate.

Narrative: Preparing to depart; running late due to weather and ATC delays; the aircraft got toasty quickly as ramp had pulled the air without giving us a signal; per usual; in non-compliance with procedure. We started the APU; waited one minute; and put the right bleed on high cold to try to stop the rising cabin temperature. Immediately there was a faint; but noticeable smell of burnt oil or something in the cockpit. First Officer (FO) asked if I smelled it and as I responded I saw smoke drifting by us outside my window; and then smoke in the cockpit almost immediately after.I told FO we needed to get the people off now; looked back to tell the A Flight Attendant (FA) to deplane everyone through the main entry/jetway; and saw smoke filling the back of the aircraft. We turned off the pack and bleed and before we could kill the APU it died; leaving us with no AC power; and just the battery. This all transpired in just a couple of seconds. About that time the aft smoke alarm sounded; followed by the forward alarm. No fire light indication was present. I called ground on VHF1; notified them of the situation and asked them to roll the fire trucks in case there was a fire.I then tuned Operations into VHF1; notified Operations; and got up to see what I could do to help in the cabin. The evacuation was going well there; so I asked FO to take care of things in the aircraft while I go see what the status of the fire trucks was; and what exterior situation was. No Passengers were showing signs of effects from smoke. They all left their belongings and moved quickly off of the aircraft. Fire and rescue personnel met me in the jetway and told me that there was no fire; but a lot of oil leaking from the tail. I confirmed that there was a large puddle of oil below the APU; with more dripping fairly quickly onto the ground.Maintenance came up and confirmed that the APU oil had leaked; causing the smoke; and said he would MEL the APU and get us on our way. I had him open the APU door and inspect for fire damage while FO and I discussed whether or not we liked the plan. Ground Operations asked if I'd like another aircraft; I said I would; and we were moved to another aircraft. Dispatch and Chief Pilot on call were contacted and briefed on all of the above. A log book entry was made.The FAs were removed and replaced. FO and I agreed that we were okay; swapped aircrafts and continued to our destination. The FAs and FO all did an excellent job; and were very professional and calm.

Data retrieved from NASA's ASRS site 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.