Narrative:

ATIS information instructed us to check our density altitude, which we did (it was +/-10000') and that all departures were using runway 17 with the wind being from 160 degrees at 6 KTS. Ground control cleared us to taxi to runway 17. While we were taxiing out ground control asked if we would need to do a run up and if so, how long would it take. We answered 'yes,' and that it should take about 60 seconds (except for the run up and runway items our pre takeoff checklist had been completed at the ramp). They advised us that an air carrier flight would be taxiing out after us and indicated it would be best not to delay its departure. At the hold line for runway 17 we completed our runup and pretkof checklist within the 60 second time limit and advised tower 'ready in sequence.' tower advised us to 'hold short for landing traffic.' we acknowledged the hold and waited while a heavy jet landed and the air carrier jet taxied up behind us. As the landing just passed we anticipated a clearance for an immediate takeoff and began preparing for same by revving up the engines, closing the windows and doors providing us ventilation, turning on the boost pumps and radar and noting the time. As anticipated, tower advised 'cleared for immediate takeoff on runway 12.' at the work 'takeoff' we released our brakes and began rolling forward over the hold line. On hearing the balance of the clearance, which assigned a new runway, we stopped short of the line marking the side of runway 17, advised tower we were unable to accept that clearance, turned around and taxied back behind the air carrier flight to await resequencing. (Please note that at cos runway 17 is 11021' and runway 12 is 8511'. At our weight and density altitude we wanted the extra runway.) at this point a new voice came on the radio and advised us that we never should have commenced to taxi if we could not accept the clearance. The problem arose with our being urged not to delay the air carrier flight while taxiing out and the hearing as the first part of an unexpected clearance the clearance we were expecting (due to the ATIS and ground control). In the past it's been my experience that when tower wanted to change runways, or clear us from an intersection, they would ask, 'can you accept...'

Related reports:

Google
 

Original NASA ASRS Text

Title: TWR CLEARED ACFT FOR TKOF ON OTHER THAN THE ASSIGNED RWY.

Narrative: ATIS INFO INSTRUCTED US TO CHK OUR DENSITY ALT, WHICH WE DID (IT WAS +/-10000') AND THAT ALL DEPS WERE USING RWY 17 WITH THE WIND BEING FROM 160 DEGS AT 6 KTS. GND CTL CLRED US TO TAXI TO RWY 17. WHILE WE WERE TAXIING OUT GND CTL ASKED IF WE WOULD NEED TO DO A RUN UP AND IF SO, HOW LONG WOULD IT TAKE. WE ANSWERED 'YES,' AND THAT IT SHOULD TAKE ABOUT 60 SECS (EXCEPT FOR THE RUN UP AND RWY ITEMS OUR PRE TKOF CHKLIST HAD BEEN COMPLETED AT THE RAMP). THEY ADVISED US THAT AN ACR FLT WOULD BE TAXIING OUT AFTER US AND INDICATED IT WOULD BE BEST NOT TO DELAY ITS DEP. AT THE HOLD LINE FOR RWY 17 WE COMPLETED OUR RUNUP AND PRETKOF CHKLIST WITHIN THE 60 SEC TIME LIMIT AND ADVISED TWR 'READY IN SEQUENCE.' TWR ADVISED US TO 'HOLD SHORT FOR LNDG TFC.' WE ACKNOWLEDGED THE HOLD AND WAITED WHILE A HVY JET LANDED AND THE ACR JET TAXIED UP BEHIND US. AS THE LNDG JUST PASSED WE ANTICIPATED A CLRNC FOR AN IMMEDIATE TKOF AND BEGAN PREPARING FOR SAME BY REVVING UP THE ENGS, CLOSING THE WINDOWS AND DOORS PROVIDING US VENTILATION, TURNING ON THE BOOST PUMPS AND RADAR AND NOTING THE TIME. AS ANTICIPATED, TWR ADVISED 'CLRED FOR IMMEDIATE TKOF ON RWY 12.' AT THE WORK 'TKOF' WE RELEASED OUR BRAKES AND BEGAN ROLLING FORWARD OVER THE HOLD LINE. ON HEARING THE BALANCE OF THE CLRNC, WHICH ASSIGNED A NEW RWY, WE STOPPED SHORT OF THE LINE MARKING THE SIDE OF RWY 17, ADVISED TWR WE WERE UNABLE TO ACCEPT THAT CLRNC, TURNED AROUND AND TAXIED BACK BEHIND THE ACR FLT TO AWAIT RESEQUENCING. (PLEASE NOTE THAT AT COS RWY 17 IS 11021' AND RWY 12 IS 8511'. AT OUR WT AND DENSITY ALT WE WANTED THE EXTRA RWY.) AT THIS POINT A NEW VOICE CAME ON THE RADIO AND ADVISED US THAT WE NEVER SHOULD HAVE COMMENCED TO TAXI IF WE COULD NOT ACCEPT THE CLRNC. THE PROB AROSE WITH OUR BEING URGED NOT TO DELAY THE ACR FLT WHILE TAXIING OUT AND THE HEARING AS THE FIRST PART OF AN UNEXPECTED CLRNC THE CLRNC WE WERE EXPECTING (DUE TO THE ATIS AND GND CTL). IN THE PAST IT'S BEEN MY EXPERIENCE THAT WHEN TWR WANTED TO CHANGE RWYS, OR CLR US FROM AN INTXN, THEY WOULD ASK, 'CAN YOU ACCEPT...'

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.