Narrative:

We were arriving on the sadde 6 arrival routing over R25 and vtu. We crossed vtu at 11000 ft and then were told to descend to 10000 ft then later (about 7 mi from smo) down to 7000 ft. There was no minimum crossing altitude stipulated, and no request was made for us to 'expedite.' we were about 7 mi in trail of a B747 and were in a slow descent (about 700 FPM) to stay above the wake. Just after crossing smo, our TCASII alerted us to a threat aircraft at 12 O'clock position at 1 mi, 200 ft above. I disconnected the autoplt upon acquiring visual on the aircraft (looked like a piper cherokee). I increased the descent rate to create more space between us and the threat aircraft. The controller said nothing. Upon inquiry the controller scolded us for descending slower than he had expected. He also mentioned that the threat aircraft was in a VFR corridor, which is not shown on any of my charts. Perhaps they should give us crossing restrs (maximum authority/authorized altitude) to avoid such conflicts in the future.

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Original NASA ASRS Text

Title: NMAC IN THE LAX CLASS B AIRSPACE BTWN ACR AND A GA ACFT SUPPOSEDLY IN THE VFR CORRIDOR.

Narrative: WE WERE ARRIVING ON THE SADDE 6 ARR ROUTING OVER R25 AND VTU. WE CROSSED VTU AT 11000 FT AND THEN WERE TOLD TO DSND TO 10000 FT THEN LATER (ABOUT 7 MI FROM SMO) DOWN TO 7000 FT. THERE WAS NO MINIMUM XING ALT STIPULATED, AND NO REQUEST WAS MADE FOR US TO 'EXPEDITE.' WE WERE ABOUT 7 MI IN TRAIL OF A B747 AND WERE IN A SLOW DSCNT (ABOUT 700 FPM) TO STAY ABOVE THE WAKE. JUST AFTER XING SMO, OUR TCASII ALERTED US TO A THREAT ACFT AT 12 O'CLOCK POS AT 1 MI, 200 FT ABOVE. I DISCONNECTED THE AUTOPLT UPON ACQUIRING VISUAL ON THE ACFT (LOOKED LIKE A PIPER CHEROKEE). I INCREASED THE DSCNT RATE TO CREATE MORE SPACE BTWN US AND THE THREAT ACFT. THE CTLR SAID NOTHING. UPON INQUIRY THE CTLR SCOLDED US FOR DSNDING SLOWER THAN HE HAD EXPECTED. HE ALSO MENTIONED THAT THE THREAT ACFT WAS IN A VFR CORRIDOR, WHICH IS NOT SHOWN ON ANY OF MY CHARTS. PERHAPS THEY SHOULD GIVE US XING RESTRS (MAX AUTH ALT) TO AVOID SUCH CONFLICTS IN THE FUTURE.

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.