Medium Transport; Low Wing; 2 Turbojet Eng
Flight Crew Air Transport Pilot (ATP)
Deviation / Discrepancy - Procedural Clearance; Ground Incursion Taxiway
Air Traffic Control Issued Advisory / Alert; Air Traffic Control Issued New Clearance; Flight Crew Became Reoriented
Human Factors; Procedure
Received taxi instructions from Ground. 'Charlie; Alpha; Sierra; clear to cross 27'. After reading back clearance my head was turned and I was busy with using iPad for charts due to EFB inop. Captain made turn on Victor to cross runway at Sierra versus instructions to cross at Charlie. I didn't notice turn until plane was too far established on Victor; notified Captain of our error had consequently received new taxi instructions/clearance from Ground. After discussion Captain indicated he had expectation bias on utilizing taxiway Victor. There was also nonstandard clearance phraseology by ATC by saying 'clear to cross 27' instead of specifying which taxiway to cross the runway i.e. 'Clear to cross 27 on Charlie; Alpha; Sierra.' ATC clearances should be given in sequential order of events to take place and eliminating any assumptions needed to interpret what was said.
We were given; 'Charlie Alpha Sierra cross 27.' I turned left on Victor and the First Officer told me that we were cleared to cross at Charlie and I slowed my taxi to a crawl. Two seconds later Ground Control informed us that we were cleared Charlie Alpha Sierra but to continue Victor Sierra and that it was not a problem. The rest of the taxi and flight was uneventful. Expectation bias. I had taxied Charlie Victor Sierra so many times in the previous week that that is what was in my head. I did not verbalize our taxi clearance as I normally do. The First Officer had turned to his iPad (EFB MEL'D) to turn from the parking diagram to the taxi chart so his head was turned as I made the wrong turn; whereas he would normally be heads up .. Ground Control issued our taxi clearance in an odd format; 'Charlie Alpha Sierra cross 27;' as opposed to cross 27 at Charlie Alpha Sierra but ultimately I screwed up and it was expectation bias.
Air carrier flight crew describes a taxiway incursion caused by the Captain's expectation bias to follow the normal route; while this clearance was slightly different.