Narrative:

Sea ATIS announced runway 34L as departure runway. Ground told us to taxi to runway 34L, hold short of runway 34R at intersection Q. Approaching intersection Q we were cleared to taxi across runway 34R, cleared for takeoff runway 34L. We advised tower we were not ready because we didn't have our final numbers for weight and balance. We were told to hold short of runway 34R. Later, when we advised tower we were ready, we heard 'taxi into position and hold runway 34L. Traffic 6 mi out for that runway. Traffic on a left base for runway 34R.' the first officer read back 'into position and hold runway 34L.' while crossing runway 34R at taxiway Q, I saw the 6 mi final for runway 34R. While approaching runway 34L, I saw a small airplane on a left base. However, it appeared that he was going to runway 34L. I slowed my taxi and was going to query the tower prior to entering runway 34L, but tower then called and said hold short runway 34L. Tower then asked 'what don't you understand about position and hold runway 34R?' without replaying the tapes, I'm now not sure what exactly was said. Thinking back, I didn't hear tower say 'cross runway 34R, taxi into position and hold,' which was a clue. But I also didn't hear 'taxi into position and hold on runway 34R at intersection Q' either, which would be required for an intersection takeoff. I, the first officer, and a cockpit observer all thought the tower said position and hold runway 34L, but it is possible that the TA's concerning the left base to runway 34L led us toward the left runway. In summary, 3 of us heard 'into position and hold runway 34L,' whether that was in fact the case or not. The first officer read back 'into position and hold runway 34L' which, if was not our clearance, should have been caught by the tower. If we were cleared onto hold for runway 34R, the clearance should have included the intersection, since the approach end of runway 34R is 2500 ft further down the runway. We didn't hear 'cross runway 34R, taxi into position and hold runway 34L' which, if we thought we were to be on runway 34L, should have prompted us to question the clearance. Because we checked final approachs when crossing and approaching the runways, we saw a potential conflict and were able to avoid taxiing onto a runway that another aircraft was about to land on.

Related reports:

Google
 

Original NASA ASRS Text

Title: NON ADHERENCE TO ATC CLRNC INSTRUCTION.

Narrative: SEA ATIS ANNOUNCED RWY 34L AS DEP RWY. GND TOLD US TO TAXI TO RWY 34L, HOLD SHORT OF RWY 34R AT INTXN Q. APCHING INTXN Q WE WERE CLRED TO TAXI ACROSS RWY 34R, CLRED FOR TKOF RWY 34L. WE ADVISED TWR WE WERE NOT READY BECAUSE WE DIDN'T HAVE OUR FINAL NUMBERS FOR WT AND BAL. WE WERE TOLD TO HOLD SHORT OF RWY 34R. LATER, WHEN WE ADVISED TWR WE WERE READY, WE HEARD 'TAXI INTO POS AND HOLD RWY 34L. TFC 6 MI OUT FOR THAT RWY. TFC ON A L BASE FOR RWY 34R.' THE FO READ BACK 'INTO POS AND HOLD RWY 34L.' WHILE XING RWY 34R AT TXWY Q, I SAW THE 6 MI FINAL FOR RWY 34R. WHILE APCHING RWY 34L, I SAW A SMALL AIRPLANE ON A L BASE. HOWEVER, IT APPEARED THAT HE WAS GOING TO RWY 34L. I SLOWED MY TAXI AND WAS GOING TO QUERY THE TWR PRIOR TO ENTERING RWY 34L, BUT TWR THEN CALLED AND SAID HOLD SHORT RWY 34L. TWR THEN ASKED 'WHAT DON'T YOU UNDERSTAND ABOUT POS AND HOLD RWY 34R?' WITHOUT REPLAYING THE TAPES, I'M NOW NOT SURE WHAT EXACTLY WAS SAID. THINKING BACK, I DIDN'T HEAR TWR SAY 'CROSS RWY 34R, TAXI INTO POS AND HOLD,' WHICH WAS A CLUE. BUT I ALSO DIDN'T HEAR 'TAXI INTO POS AND HOLD ON RWY 34R AT INTXN Q' EITHER, WHICH WOULD BE REQUIRED FOR AN INTXN TKOF. I, THE FO, AND A COCKPIT OBSERVER ALL THOUGHT THE TWR SAID POS AND HOLD RWY 34L, BUT IT IS POSSIBLE THAT THE TA'S CONCERNING THE L BASE TO RWY 34L LED US TOWARD THE L RWY. IN SUMMARY, 3 OF US HEARD 'INTO POS AND HOLD RWY 34L,' WHETHER THAT WAS IN FACT THE CASE OR NOT. THE FO READ BACK 'INTO POS AND HOLD RWY 34L' WHICH, IF WAS NOT OUR CLRNC, SHOULD HAVE BEEN CAUGHT BY THE TWR. IF WE WERE CLRED ONTO HOLD FOR RWY 34R, THE CLRNC SHOULD HAVE INCLUDED THE INTXN, SINCE THE APCH END OF RWY 34R IS 2500 FT FURTHER DOWN THE RWY. WE DIDN'T HEAR 'CROSS RWY 34R, TAXI INTO POS AND HOLD RWY 34L' WHICH, IF WE THOUGHT WE WERE TO BE ON RWY 34L, SHOULD HAVE PROMPTED US TO QUESTION THE CLRNC. BECAUSE WE CHKED FINAL APCHS WHEN XING AND APCHING THE RWYS, WE SAW A POTENTIAL CONFLICT AND WERE ABLE TO AVOID TAXIING ONTO A RWY THAT ANOTHER ACFT WAS ABOUT TO LAND ON.

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.