Narrative:

We were on a 240 degree radar vector heading to intercept sfo 095 degree radial descending out of 8300 ft for our cleared altitude of 8000. ATC issued VFR traffic at 1 O'clock 3 mi a few moments later we received a 'TA' warning. I ringed the TCASII down to 5 mi scale and observed the target at 1 O'clock, 3 mi, 1300 ft below us and climbing. ATC issued a 10 degree left turn to intercept sfo 095 degree radial. As we turned the target became a RA. The target was at 1 O'clock, 400 ft below us, converging to within 1/2 to 3/4 of a mi. While responding to the RA, the controller issued a clearance to 7000 ft. I advised the controller we were unable to accept the clearance as we were responding to a 'RA'. The controller said he would note that we couldn't accept the clearance. Within 5 seconds the target cleared to our right and rear. I advised ATC we could not accept a descent. We were cleared to 7000 and given a frequency change. We proceeded to sfo. The length of time from 'TA' to 'clear of conflict' was 25-30 seconds. The time during which we were unable to accept the descent clearance was about 5 seconds. Since we were still north of the sfo 090 degree radial at 21 mi we had not entered the sfo TCA. Thus, no communications was required of the VFR traffic. His rapid climb and closure to within 400 ft set off the TCASII resolution. Our location and altitude was not a 'healthy' place for a VFR aircraft to cross the arrival stream of aircraft for sfo.

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Original NASA ASRS Text

Title: ACR MLG FLC UNABLE TO ACCEPT AMENDED ALT ASSIGNMENT CLRNC ACCOUNT TCASII RA.

Narrative: WE WERE ON A 240 DEG RADAR VECTOR HDG TO INTERCEPT SFO 095 DEG RADIAL DSNDING OUT OF 8300 FT FOR OUR CLRED ALT OF 8000. ATC ISSUED VFR TFC AT 1 O'CLOCK 3 MI A FEW MOMENTS LATER WE RECEIVED A 'TA' WARNING. I RINGED THE TCASII DOWN TO 5 MI SCALE AND OBSERVED THE TARGET AT 1 O'CLOCK, 3 MI, 1300 FT BELOW US AND CLBING. ATC ISSUED A 10 DEG L TURN TO INTERCEPT SFO 095 DEG RADIAL. AS WE TURNED THE TARGET BECAME A RA. THE TARGET WAS AT 1 O'CLOCK, 400 FT BELOW US, CONVERGING TO WITHIN 1/2 TO 3/4 OF A MI. WHILE RESPONDING TO THE RA, THE CTLR ISSUED A CLRNC TO 7000 FT. I ADVISED THE CTLR WE WERE UNABLE TO ACCEPT THE CLRNC AS WE WERE RESPONDING TO A 'RA'. THE CTLR SAID HE WOULD NOTE THAT WE COULDN'T ACCEPT THE CLRNC. WITHIN 5 SECONDS THE TARGET CLRED TO OUR R AND REAR. I ADVISED ATC WE COULD NOT ACCEPT A DSCNT. WE WERE CLRED TO 7000 AND GIVEN A FREQ CHANGE. WE PROCEEDED TO SFO. THE LENGTH OF TIME FROM 'TA' TO 'CLR OF CONFLICT' WAS 25-30 SECONDS. THE TIME DURING WHICH WE WERE UNABLE TO ACCEPT THE DSCNT CLRNC WAS ABOUT 5 SECONDS. SINCE WE WERE STILL N OF THE SFO 090 DEG RADIAL AT 21 MI WE HAD NOT ENTERED THE SFO TCA. THUS, NO COMS WAS REQUIRED OF THE VFR TFC. HIS RAPID CLB AND CLOSURE TO WITHIN 400 FT SET OFF THE TCASII RESOLUTION. OUR LOCATION AND ALT WAS NOT A 'HEALTHY' PLACE FOR A VFR ACFT TO CROSS THE ARR STREAM OF ACFT FOR SFO.

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.