Narrative:

While being vectored for approach to runway 19L at sfo, received conflicting clrncs. Approximately, 26-27 DME from airport in IMC with light chop and light rime at 10000 ft MSL and 270 degree vector, we received an altitude clearance to 8000 ft MSL and a left turn vector to 260 degrees. So was updating the ATIS and captain (PNF) missed clearance. First officer (PF) reset altitude alert system to 8000 ft. Another aircraft transmitted before our acknowledgment. Captain acknowledged 8000 ft and left turn to 260 degrees. We received no correction or follow up to transmission. During stabilized descent of approximately 700-800 FPM and passing 8400- 8500 ft MSL, the bay approach controller transmitted maintain 9000 ft and turn left to 240 degrees. The first officer (PF) immediately reversed descent to climb up to 9000 ft MSL. The captain transmitted back the clearance (9000 ft/240 degrees) and relayed that we had acknowledged a previous clearance to 8000 ft MSL. The TCASII did not display any conflicts or aircraft in our immediate vicinity. The controller did not display any undue concern or reply to the captain's transmission of the previously acknowledged clearance. The remainder of flight and approach were uneventful. The controller appeared calm and in control, but very busy -- maybe working multiple frequencys. The flight itself was long (cvg-sfo) about 4.5 hours. No other factors affecting the flight come to mind.

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Original NASA ASRS Text

Title: AN ACR B727 FLC RESPONDED TO ANOTHER'S CLRNC AND DSNDED AND TURNED BASE ON THAT CLRNC.

Narrative: WHILE BEING VECTORED FOR APCH TO RWY 19L AT SFO, RECEIVED CONFLICTING CLRNCS. APPROX, 26-27 DME FROM ARPT IN IMC WITH LIGHT CHOP AND LIGHT RIME AT 10000 FT MSL AND 270 DEG VECTOR, WE RECEIVED AN ALT CLRNC TO 8000 FT MSL AND A L TURN VECTOR TO 260 DEGS. SO WAS UPDATING THE ATIS AND CAPT (PNF) MISSED CLRNC. FO (PF) RESET ALT ALERT SYS TO 8000 FT. ANOTHER ACFT XMITTED BEFORE OUR ACKNOWLEDGMENT. CAPT ACKNOWLEDGED 8000 FT AND L TURN TO 260 DEGS. WE RECEIVED NO CORRECTION OR FOLLOW UP TO XMISSION. DURING STABILIZED DSCNT OF APPROX 700-800 FPM AND PASSING 8400- 8500 FT MSL, THE BAY APCH CTLR XMITTED MAINTAIN 9000 FT AND TURN L TO 240 DEGS. THE FO (PF) IMMEDIATELY REVERSED DSCNT TO CLB UP TO 9000 FT MSL. THE CAPT XMITTED BACK THE CLRNC (9000 FT/240 DEGS) AND RELAYED THAT WE HAD ACKNOWLEDGED A PREVIOUS CLRNC TO 8000 FT MSL. THE TCASII DID NOT DISPLAY ANY CONFLICTS OR ACFT IN OUR IMMEDIATE VICINITY. THE CTLR DID NOT DISPLAY ANY UNDUE CONCERN OR REPLY TO THE CAPT'S XMISSION OF THE PREVIOUSLY ACKNOWLEDGED CLRNC. THE REMAINDER OF FLT AND APCH WERE UNEVENTFUL. THE CTLR APPEARED CALM AND IN CTL, BUT VERY BUSY -- MAYBE WORKING MULTIPLE FREQS. THE FLT ITSELF WAS LONG (CVG-SFO) ABOUT 4.5 HRS. NO OTHER FACTORS AFFECTING THE FLT COME TO MIND.

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.