Narrative:

So as not to delay aircraft taxiing behind us, the captain had the first officer tell pit ground control that we would be delayed a few mins while the flight attendants completed their safety announcement. We were instructed to hold short of taxiway west on taxiway D, and we complied. A couple of mins later, we called ready for taxi and pit ground control issued a taxi clearance to runway 10C (and perhaps a taxi into position clearance. This is where the confusion begins.) the captain called for the final items of the before takeoff checklist, which the first officer performed heads down, as is necessary. Under the impression that we had been cleared into position, the captain taxied onto the overrun section of runway 28C which is several hundred ft from the runway 10C threshold. The first officer completed the checklist, looked up and expressed concern that we had not been cleared into position and hold, whereas the captain was certain we had. Neither the captain nor first officer could recall the exact words from the pit ground controller, so the first officer announced 'air carrier X ready for takeoff'. The tower issued a 'cleared for takeoff' without any apparent concern, confusion or irritation. We, therefore, concluded that we had, in fact, been issued 'position and hold' clearance. The takeoff clearance was issued prior to us reaching the runway 10C threshold. The takeoff and subsequent handoff to departure control continued normally without comment. Supplemental information from acn 546734: captain called for the final items of the before takeoff checklist which the first officer performed heads down. The captain taxied onto the overrun of runway 28C under the assumption that we were cleared into position runway 10C and hold. Capts should not call 'below the line' until takeoff or position and hold so that the first officer is heads up while taxiing onto the runway.

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Original NASA ASRS Text

Title: AN A319 CAPT, TAXIING FOR TKOF AT PIT, TAXIED INTO POS, WHILE FO WAS UNSURE IF THEY WERE CLRED TO DO SO.

Narrative: SO AS NOT TO DELAY ACFT TAXIING BEHIND US, THE CAPT HAD THE FO TELL PIT GND CTL THAT WE WOULD BE DELAYED A FEW MINS WHILE THE FLT ATTENDANTS COMPLETED THEIR SAFETY ANNOUNCEMENT. WE WERE INSTRUCTED TO HOLD SHORT OF TXWY W ON TXWY D, AND WE COMPLIED. A COUPLE OF MINS LATER, WE CALLED READY FOR TAXI AND PIT GND CTL ISSUED A TAXI CLRNC TO RWY 10C (AND PERHAPS A TAXI INTO POS CLRNC. THIS IS WHERE THE CONFUSION BEGINS.) THE CAPT CALLED FOR THE FINAL ITEMS OF THE BEFORE TKOF CHKLIST, WHICH THE FO PERFORMED HEADS DOWN, AS IS NECESSARY. UNDER THE IMPRESSION THAT WE HAD BEEN CLRED INTO POS, THE CAPT TAXIED ONTO THE OVERRUN SECTION OF RWY 28C WHICH IS SEVERAL HUNDRED FT FROM THE RWY 10C THRESHOLD. THE FO COMPLETED THE CHKLIST, LOOKED UP AND EXPRESSED CONCERN THAT WE HAD NOT BEEN CLRED INTO POS AND HOLD, WHEREAS THE CAPT WAS CERTAIN WE HAD. NEITHER THE CAPT NOR FO COULD RECALL THE EXACT WORDS FROM THE PIT GND CTLR, SO THE FO ANNOUNCED 'ACR X READY FOR TKOF'. THE TWR ISSUED A 'CLRED FOR TKOF' WITHOUT ANY APPARENT CONCERN, CONFUSION OR IRRITATION. WE, THEREFORE, CONCLUDED THAT WE HAD, IN FACT, BEEN ISSUED 'POS AND HOLD' CLRNC. THE TKOF CLRNC WAS ISSUED PRIOR TO US REACHING THE RWY 10C THRESHOLD. THE TKOF AND SUBSEQUENT HDOF TO DEP CTL CONTINUED NORMALLY WITHOUT COMMENT. SUPPLEMENTAL INFO FROM ACN 546734: CAPT CALLED FOR THE FINAL ITEMS OF THE BEFORE TKOF CHKLIST WHICH THE FO PERFORMED HEADS DOWN. THE CAPT TAXIED ONTO THE OVERRUN OF RWY 28C UNDER THE ASSUMPTION THAT WE WERE CLRED INTO POS RWY 10C AND HOLD. CAPTS SHOULD NOT CALL 'BELOW THE LINE' UNTIL TKOF OR POS AND HOLD SO THAT THE FO IS HEADS UP WHILE TAXIING ONTO THE RWY.

Data retrieved from NASA's ASRS site as of July 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.