Narrative:

After leaving bolder fix (oak 151 degree right/34) on the big sur profile descent and descending to 6000', we reported sfo in sight to bay approach on 135.65. Bay told us to descend to 5000' (normally 4000') for traffic departing moffett NAS. After leveling at 5000' bay asked us to report widebody transport traffic in sight at 12 O'clock and 4 mi (widebody transport was landing on 28R). After we called the widebody transport in sight bay said 'turn 10 left, maintain visibility with the widebody transport, you are cleared for 28L, the widebody transport is for 28R.' we acknowledged, 'we'll maintain visibility with the widebody transport, we're cleared for 28L.' we started to descend (our position now was inside the oak 151 degree right, 16 DME). Approaching 4000' bay advised us 'traffic off moffett is no longer a factor, you are cleared for tipp toe visibility approach 28L, contact tower on 120.5.' this suggested to us that we were not cleared the visibility approach before we left the last assigned altitude. We felt we received approach clearance before leaving 5000', although after looking back the clearance did seem ambiguous. 'Cleared for 28L'--the runway, but not the descent or approach. The obvious solution before descending would have been to ask if we were cleared for the tipp toe visibility approach to 28L. Supplemental information from acn 138167: we had the widebody transport in sight, so there was no conflict.

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Original NASA ASRS Text

Title: ACR MLG GIVEN AMBIGUOUS CLRNC FROM BIG SUR PROFILE DESCENT TO WHAT THE FLT CREW BELIEVES IS THE TIPTOE VISUAL APCH TO SFO.

Narrative: AFTER LEAVING BOLDER FIX (OAK 151 DEG R/34) ON THE BIG SUR PROFILE DSCNT AND DSNDING TO 6000', WE RPTED SFO IN SIGHT TO BAY APCH ON 135.65. BAY TOLD US TO DSND TO 5000' (NORMALLY 4000') FOR TFC DEPARTING MOFFETT NAS. AFTER LEVELING AT 5000' BAY ASKED US TO RPT WDB TFC IN SIGHT AT 12 O'CLOCK AND 4 MI (WDB WAS LNDG ON 28R). AFTER WE CALLED THE WDB IN SIGHT BAY SAID 'TURN 10 LEFT, MAINTAIN VIS WITH THE WDB, YOU ARE CLRED FOR 28L, THE WDB IS FOR 28R.' WE ACKNOWLEDGED, 'WE'LL MAINTAIN VIS WITH THE WDB, WE'RE CLRED FOR 28L.' WE STARTED TO DSND (OUR POS NOW WAS INSIDE THE OAK 151 DEG R, 16 DME). APCHING 4000' BAY ADVISED US 'TFC OFF MOFFETT IS NO LONGER A FACTOR, YOU ARE CLRED FOR TIPP TOE VIS APCH 28L, CONTACT TWR ON 120.5.' THIS SUGGESTED TO US THAT WE WERE NOT CLRED THE VIS APCH BEFORE WE LEFT THE LAST ASSIGNED ALT. WE FELT WE RECEIVED APCH CLRNC BEFORE LEAVING 5000', ALTHOUGH AFTER LOOKING BACK THE CLRNC DID SEEM AMBIGUOUS. 'CLRED FOR 28L'--THE RWY, BUT NOT THE DSCNT OR APCH. THE OBVIOUS SOLUTION BEFORE DSNDING WOULD HAVE BEEN TO ASK IF WE WERE CLRED FOR THE TIPP TOE VIS APCH TO 28L. SUPPLEMENTAL INFO FROM ACN 138167: WE HAD THE WDB IN SIGHT, SO THERE WAS NO CONFLICT.

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.