Narrative:

On a scheduled flight from rno-sfo, we were cleared by ATC off our filed route to cross a point 20 DME from sfo at what I and my first officer believed to be an altitude of 10000' and 250 KIAS. I told the controller we would have difficulty in compliance and he replied that the speed of 250 KIAS at 20 DME would be sufficient and to give best descent rate. Well, we made the crossing restriction at 10000' and 250 KIAS and were told to contact bay approach. After several unsuccessful attempts to get a reply on approach frequency, I returned to center frequency and asked if I had the correct frequency. At this point I was asked what my altitude was, and I replied 10000'. I was told I was assigned 11000'. I indicated I felt sure I had replied 10000' on the original clearance and he replied to maintain 10000' and contact bay approach. I asked if there was any problem and he replied that there had not been. I now feel some doubt in my mind as to what altitude I was assigned, however both myself and first officer mentally accepted 10000' as our assigned altitude, and that was also the altitude set in the altitude alert system on board immediately upon reading back descent clearance. Perhaps alert system should be also backed up with note on scratch pad to aid in accuracy and act as back up to system, although up to now I've found alert system to be sufficient tool for awareness. Just a note: I am very new to west coast flying, having spent most of my yrs in the eastern routes. Several times now I have found myself expediting to make crossing restrictions because, I think, the controller assumed I knew what to expect. I think the eastern ATC centers give a pilot more information on what to anticipate and this makes for a more pleasant flight. A STAR I can read, his mind I can't.

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Original NASA ASRS Text

Title: CLRNC INTERP RESULTING IN DESCENDING TO 10000' VERSUS ASSIGNED ALT 11000'.

Narrative: ON A SCHEDULED FLT FROM RNO-SFO, WE WERE CLRED BY ATC OFF OUR FILED ROUTE TO CROSS A POINT 20 DME FROM SFO AT WHAT I AND MY F/O BELIEVED TO BE AN ALT OF 10000' AND 250 KIAS. I TOLD THE CTLR WE WOULD HAVE DIFFICULTY IN COMPLIANCE AND HE REPLIED THAT THE SPD OF 250 KIAS AT 20 DME WOULD BE SUFFICIENT AND TO GIVE BEST DSCNT RATE. WELL, WE MADE THE XING RESTRICTION AT 10000' AND 250 KIAS AND WERE TOLD TO CONTACT BAY APCH. AFTER SEVERAL UNSUCCESSFUL ATTEMPTS TO GET A REPLY ON APCH FREQ, I RETURNED TO CENTER FREQ AND ASKED IF I HAD THE CORRECT FREQ. AT THIS POINT I WAS ASKED WHAT MY ALT WAS, AND I REPLIED 10000'. I WAS TOLD I WAS ASSIGNED 11000'. I INDICATED I FELT SURE I HAD REPLIED 10000' ON THE ORIGINAL CLRNC AND HE REPLIED TO MAINTAIN 10000' AND CONTACT BAY APCH. I ASKED IF THERE WAS ANY PROB AND HE REPLIED THAT THERE HAD NOT BEEN. I NOW FEEL SOME DOUBT IN MY MIND AS TO WHAT ALT I WAS ASSIGNED, HOWEVER BOTH MYSELF AND F/O MENTALLY ACCEPTED 10000' AS OUR ASSIGNED ALT, AND THAT WAS ALSO THE ALT SET IN THE ALT ALERT SYS ON BOARD IMMEDIATELY UPON READING BACK DSCNT CLRNC. PERHAPS ALERT SYS SHOULD BE ALSO BACKED UP WITH NOTE ON SCRATCH PAD TO AID IN ACCURACY AND ACT AS BACK UP TO SYS, ALTHOUGH UP TO NOW I'VE FOUND ALERT SYS TO BE SUFFICIENT TOOL FOR AWARENESS. JUST A NOTE: I AM VERY NEW TO W COAST FLYING, HAVING SPENT MOST OF MY YRS IN THE EASTERN ROUTES. SEVERAL TIMES NOW I HAVE FOUND MYSELF EXPEDITING TO MAKE XING RESTRICTIONS BECAUSE, I THINK, THE CTLR ASSUMED I KNEW WHAT TO EXPECT. I THINK THE EASTERN ATC CENTERS GIVE A PLT MORE INFO ON WHAT TO ANTICIPATE AND THIS MAKES FOR A MORE PLEASANT FLT. A STAR I CAN READ, HIS MIND I CAN'T.

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.