B777 Undifferentiated or Other Model
Flight Crew Instrument; Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 198; Flight Crew Total 30000; Flight Crew Type 1356
Fatigue; Troubleshooting
Flight Deck / Cabin / Aircraft Event Smoke / Fire / Fumes / Odor; Ground Event / Encounter Other / Unknown
General Work Refused; General Maintenance Action; General Flight Cancelled / Delayed
Aircraft
We started the APU and turned the packs on. The entire plane filled with a smoky haze with a strong old sock smell. The smoke cleared in a few minutes but the smell continued. We called for a mechanic. Unknown to us the fire department was called out due to smoke from cargo hold. We had no indications in the cockpit. They checked it out and found no fire. Maintenance believed smoke was from APU oil leaking into air system. This resulted in having to get a new plane from the hangar and a long rolling delay. We found out the plane needed to be cleaned also so the last XA:15 am departure time posted was not going to happen. My First Officer and I agreed we were not safe to operate the flight.
B777 Captain reported 'strong old sock odor' during pre-flight at the gate resulting in maintenance inspection and ultimately an aircraft swap.  The new aircraft required cleaning causing further delays.  The flight crew decided they were unfit to fly due to all the delays.