Narrative:

Air carrier X cleared to cross 6 mi northwest of sfo at 11000 ft at 250 KTS. We were not on the golden gate 3 arrival, nor cleared as such. We questioned the clearance and it was repeated. The controller 'stumbled' over his words and we asked him to acknowledge if it was 6 mi or 6000 ft. He stated '06,' however, we were now descending rapidly and realized we had to level at 11000 ft - the controller transmitted that we climb back to 11000 ft - we acknowledged and leveled off at 10300 ft and initiated a climb back to 11000 ft. I feel if we were given the golden gate arrival to cross lestr (which is 6 NM northwest of sfo) all problems could have been a avoided. A miscom and understanding prevailed. If we'd have requested or been assigned the golden gate 3 arrival I feel the FMS/vertical navigation would have been programmed and all problems avoided. Supplemental information from acn 299620: approach control cleared (us) to, what I thought was a point 60 northwest of sfo at 11000 ft. I questioned the first officer about the clearance. He thought 6, not 60, mi. As 1 route was direct pye direct sfo, both of us had doubts. We again questioned approach and he read back zero six mi, north of sfo at 11000 ft. Still unsure, we had a cockpit discussion. I had written the clearance down incorrectly. The readback was slurred the second time. The 11000 ft was correct, but where? For whatever reason I had 6000 ft in my mind and rolled 6000 ft into the FMS. I slowed early from 290 KTS to 250 KTS with doubts still in my mind. We were driving directly into the sun. I know the first officer couldn't see the FMS without special effort, as I couldn't either. The debate in the cockpit continued as to the clearance. I rolled zero vertical/speed into the FMS, not wanting to descend on a doubtful clearance. We leveled at 10500 ft. Approach asked us what we were doing, we responded clearance to 6000 ft. They told us clearance was to 11000 ft and climb back to 11000 ft.

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Original NASA ASRS Text

Title: ACR X UNAUTH DSCNT BELOW ASSIGNED ALT. ALTDEV.

Narrative: ACR X CLRED TO CROSS 6 MI NW OF SFO AT 11000 FT AT 250 KTS. WE WERE NOT ON THE GOLDEN GATE 3 ARR, NOR CLRED AS SUCH. WE QUESTIONED THE CLRNC AND IT WAS REPEATED. THE CTLR 'STUMBLED' OVER HIS WORDS AND WE ASKED HIM TO ACKNOWLEDGE IF IT WAS 6 MI OR 6000 FT. HE STATED '06,' HOWEVER, WE WERE NOW DSNDING RAPIDLY AND REALIZED WE HAD TO LEVEL AT 11000 FT - THE CTLR XMITTED THAT WE CLB BACK TO 11000 FT - WE ACKNOWLEDGED AND LEVELED OFF AT 10300 FT AND INITIATED A CLB BACK TO 11000 FT. I FEEL IF WE WERE GIVEN THE GOLDEN GATE ARR TO CROSS LESTR (WHICH IS 6 NM NW OF SFO) ALL PROBS COULD HAVE BEEN A AVOIDED. A MISCOM AND UNDERSTANDING PREVAILED. IF WE'D HAVE REQUESTED OR BEEN ASSIGNED THE GOLDEN GATE 3 ARR I FEEL THE FMS/VERT NAV WOULD HAVE BEEN PROGRAMMED AND ALL PROBS AVOIDED. SUPPLEMENTAL INFO FROM ACN 299620: APCH CTL CLRED (US) TO, WHAT I THOUGHT WAS A POINT 60 NW OF SFO AT 11000 FT. I QUESTIONED THE FO ABOUT THE CLRNC. HE THOUGHT 6, NOT 60, MI. AS 1 RTE WAS DIRECT PYE DIRECT SFO, BOTH OF US HAD DOUBTS. WE AGAIN QUESTIONED APCH AND HE READ BACK ZERO SIX MI, N OF SFO AT 11000 FT. STILL UNSURE, WE HAD A COCKPIT DISCUSSION. I HAD WRITTEN THE CLRNC DOWN INCORRECTLY. THE READBACK WAS SLURRED THE SECOND TIME. THE 11000 FT WAS CORRECT, BUT WHERE? FOR WHATEVER REASON I HAD 6000 FT IN MY MIND AND ROLLED 6000 FT INTO THE FMS. I SLOWED EARLY FROM 290 KTS TO 250 KTS WITH DOUBTS STILL IN MY MIND. WE WERE DRIVING DIRECTLY INTO THE SUN. I KNOW THE FO COULDN'T SEE THE FMS WITHOUT SPECIAL EFFORT, AS I COULDN'T EITHER. THE DEBATE IN THE COCKPIT CONTINUED AS TO THE CLRNC. I ROLLED ZERO VERT/SPD INTO THE FMS, NOT WANTING TO DSND ON A DOUBTFUL CLRNC. WE LEVELED AT 10500 FT. APCH ASKED US WHAT WE WERE DOING, WE RESPONDED CLRNC TO 6000 FT. THEY TOLD US CLRNC WAS TO 11000 FT AND CLB BACK TO 11000 FT.

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.