Narrative:

We were cruising wbound en route to lax on J4 about 75 mi east of tnp VOR. We were level at FL390 and were experiencing light turbulence. We requested a lower altitude from ZLA and were given a clearance to FL370. After about 1 min we noticed an aircraft in front of us on our TCASII screen indicating FL370. A few seconds later, we received a TA from the TCASII system and simultaneous instructions from ZLA to 'turn left 40 degrees and climb to FL390.' we responded immediately and were level at FL390 when the other aircraft passed abeam our right side at 3-5 mi distance. Our lowest altitude reached was FL380. Our ATC controller was immediately replaced by another and radio traffic was heavy at the time. I do not consider this event to be a near miss since we always had some lateral separation as well as 1000 ft minimum vertical separation. However, this is obviously a rare occurrence in the en route positive control environment and may have encroached on the minimum en route separation standards used by ATC. Contributing factors to this event were obviously a heavy controller workload, a saturated radio frequency, and high volume traffic arriving and departing the los angeles area. Supplemental information from acn 386387: I would like to know why controllers assign wrong way altitudes (370 wbound) in busy airspace like ZOA. Also, I am glad that we now have TCASII. It gave us instant situational awareness in a very confusing situation, and may have saved a near miss or collision.

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Original NASA ASRS Text

Title: FLC OF B767-200 IS GIVEN CLRNC TO DSND. AS THEY START DSCNT, THE TCASII SHOWS AN ACFT IN FRONT OF THEM. A TCASII TA IS GIVEN AND CTR ISSUES A TURN AND CLB BACK TO PREVIOUS ALT.

Narrative: WE WERE CRUISING WBOUND ENRTE TO LAX ON J4 ABOUT 75 MI E OF TNP VOR. WE WERE LEVEL AT FL390 AND WERE EXPERIENCING LIGHT TURB. WE REQUESTED A LOWER ALT FROM ZLA AND WERE GIVEN A CLRNC TO FL370. AFTER ABOUT 1 MIN WE NOTICED AN ACFT IN FRONT OF US ON OUR TCASII SCREEN INDICATING FL370. A FEW SECONDS LATER, WE RECEIVED A TA FROM THE TCASII SYS AND SIMULTANEOUS INSTRUCTIONS FROM ZLA TO 'TURN L 40 DEGS AND CLB TO FL390.' WE RESPONDED IMMEDIATELY AND WERE LEVEL AT FL390 WHEN THE OTHER ACFT PASSED ABEAM OUR R SIDE AT 3-5 MI DISTANCE. OUR LOWEST ALT REACHED WAS FL380. OUR ATC CTLR WAS IMMEDIATELY REPLACED BY ANOTHER AND RADIO TFC WAS HVY AT THE TIME. I DO NOT CONSIDER THIS EVENT TO BE A NEAR MISS SINCE WE ALWAYS HAD SOME LATERAL SEPARATION AS WELL AS 1000 FT MINIMUM VERT SEPARATION. HOWEVER, THIS IS OBVIOUSLY A RARE OCCURRENCE IN THE ENRTE POSITIVE CTL ENVIRONMENT AND MAY HAVE ENCROACHED ON THE MINIMUM ENRTE SEPARATION STANDARDS USED BY ATC. CONTRIBUTING FACTORS TO THIS EVENT WERE OBVIOUSLY A HVY CTLR WORKLOAD, A SATURATED RADIO FREQ, AND HIGH VOLUME TFC ARRIVING AND DEPARTING THE LOS ANGELES AREA. SUPPLEMENTAL INFO FROM ACN 386387: I WOULD LIKE TO KNOW WHY CTLRS ASSIGN WRONG WAY ALTS (370 WBOUND) IN BUSY AIRSPACE LIKE ZOA. ALSO, I AM GLAD THAT WE NOW HAVE TCASII. IT GAVE US INSTANT SITUATIONAL AWARENESS IN A VERY CONFUSING SIT, AND MAY HAVE SAVED A NEAR MISS OR COLLISION.

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.