Narrative:

On big sur 2 arrival to sfo, just prior to boldr, descending through 11800 ft, we saw an aircraft about 2 mi at 12 O'clock position on TCASII at 11000 ft. Asked center if he knew about aircraft at 11000 ft, and he said 'that is why I cleared you to 12000 ft.' both the first officer and myself clearly remember the clearance as 'cross boldr at 10000 ft. I told the controller the last clearance we had was 'boldr at 10000 ft' and he said 'must have been my mistake, level at 12000 ft.' we stopped the descent at about 11400 ft and started a climb to 12000 ft as we passed over the other aircraft. Then we were cleared to 10000 ft. Supplemental information from acn 457136: we had been cleared to stop descent at 12000 ft. We did not acknowledge or receive such a clearance/transmission. The controller stated that he must not have received our readback after he allegedly gave us the amended 12000 ft clearance.

Google
 

Original NASA ASRS Text

Title: A B737-300 FLC CALLS ATC WITH A TFC PROB AS TCASII NOTES XING TFC BELOW. THE B737 HAD LAST RECEIVED A CLRNC DSCNT THROUGH THAT OCCUPIED ALT WITH ZOA. CA.

Narrative: ON BIG SUR 2 ARR TO SFO, JUST PRIOR TO BOLDR, DSNDING THROUGH 11800 FT, WE SAW AN ACFT ABOUT 2 MI AT 12 O'CLOCK POS ON TCASII AT 11000 FT. ASKED CTR IF HE KNEW ABOUT ACFT AT 11000 FT, AND HE SAID 'THAT IS WHY I CLRED YOU TO 12000 FT.' BOTH THE FO AND MYSELF CLRLY REMEMBER THE CLRNC AS 'CROSS BOLDR AT 10000 FT. I TOLD THE CTLR THE LAST CLRNC WE HAD WAS 'BOLDR AT 10000 FT' AND HE SAID 'MUST HAVE BEEN MY MISTAKE, LEVEL AT 12000 FT.' WE STOPPED THE DSCNT AT ABOUT 11400 FT AND STARTED A CLB TO 12000 FT AS WE PASSED OVER THE OTHER ACFT. THEN WE WERE CLRED TO 10000 FT. SUPPLEMENTAL INFO FROM ACN 457136: WE HAD BEEN CLRED TO STOP DSCNT AT 12000 FT. WE DID NOT ACKNOWLEDGE OR RECEIVE SUCH A CLRNC/XMISSION. THE CTLR STATED THAT HE MUST NOT HAVE RECEIVED OUR READBACK AFTER HE ALLEGEDLY GAVE US THE AMENDED 12000 FT CLRNC.

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.