Narrative:

Received taxi clearance to 'taxi to runway 28 center,' and captain began taxi as I read after start and before takeoff checklists. My attention was diverted inside cockpit as new weight and balance information was received from company via ACARS. As I entered new data into FMC, received following message from ground control, 'you were cleared to runway 28C which you are crossing now. Back taxi into position and hold.' I acknowledged and the captain back taxied into position. The remainder of the flight was normal. I believe greater vigilance on the part of the captain is necessary due to the cockpit duties required of the first officer while taxiing (read checklist, received company messages and talk to both company and ground, and enter date into FMC's while monitoring aircraft progress).

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Original NASA ASRS Text

Title: ACR MLG TAXIED TOWARD WRONG RWY AND MADE UNAUTH RWY ENTRY AT PIT.

Narrative: RECEIVED TAXI CLRNC TO 'TAXI TO RWY 28 CENTER,' AND CAPT BEGAN TAXI AS I READ AFTER START AND BEFORE TKOF CHKLISTS. MY ATTN WAS DIVERTED INSIDE COCKPIT AS NEW WT AND BALANCE INFO WAS RECEIVED FROM COMPANY VIA ACARS. AS I ENTERED NEW DATA INTO FMC, RECEIVED FOLLOWING MESSAGE FROM GND CTL, 'YOU WERE CLRED TO RWY 28C WHICH YOU ARE XING NOW. BACK TAXI INTO POS AND HOLD.' I ACKNOWLEDGED AND THE CAPT BACK TAXIED INTO POS. THE REMAINDER OF THE FLT WAS NORMAL. I BELIEVE GREATER VIGILANCE ON THE PART OF THE CAPT IS NECESSARY DUE TO THE COCKPIT DUTIES REQUIRED OF THE F/O WHILE TAXIING (READ CHKLIST, RECEIVED COMPANY MESSAGES AND TALK TO BOTH COMPANY AND GND, AND ENTER DATE INTO FMC'S WHILE MONITORING ACFT PROGRESS).

Data retrieved from NASA's ASRS site as of August 2007 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.