Narrative:

An air carrier B737 (flight cc) passed through our altitude in a steep right turn at about 1 NM triggering a TCASII alert. In a discussion with socal approach (radar controller) it was stated that although 'normal' radar separation is 3 NM and 1000 ft vertically, that criteria can be ignored if aircraft have a 15 degree course divergence. 1) this is not a very safe way to operate. The air carrier flight was still in a turn when he went by me. What if he didn't turn? 2) having commercial airliners (with 250 people and lives at stake!) passing within 1 mi of each other at 250 KTS without both having the other in sight is not very smart (we were never even advised of air carrier's presence until we inquired about the aircraft off our left). This '15 degree course' rule is especially dangerous when a situation like ours occurs (ie, lax departing aircraft east, arrs coming from the east headed inbound on the reciprocal course of the departures). Callback conversation with reporter revealed the following information: reporter is concerned that aircraft are flying too close together. All clrncs and separations are proper, but, he feels that with large aircraft being flown, aircraft are too close together. He isn't certain that other aircraft will turn when supposed to, or that a 15 degree divergence is a good idea. He really wants more separation around him and other aircraft. Although the other aircraft was talking to TRACON, each aircraft was on a different frequency, so this reporter could not gain any information regarding the other aircraft.

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Original NASA ASRS Text

Title: A B757 RECEIVES A TCASII TA OVER DOWNEY INTXN GOING INTO LAX. CAPT IS CRITICAL OF CTLR'S PROCS THAT ALLOW IT TO HAPPEN.

Narrative: AN ACR B737 (FLT CC) PASSED THROUGH OUR ALT IN A STEEP R TURN AT ABOUT 1 NM TRIGGERING A TCASII ALERT. IN A DISCUSSION WITH SOCAL APCH (RADAR CTLR) IT WAS STATED THAT ALTHOUGH 'NORMAL' RADAR SEPARATION IS 3 NM AND 1000 FT VERTLY, THAT CRITERIA CAN BE IGNORED IF ACFT HAVE A 15 DEG COURSE DIVERGENCE. 1) THIS IS NOT A VERY SAFE WAY TO OPERATE. THE ACR FLT WAS STILL IN A TURN WHEN HE WENT BY ME. WHAT IF HE DIDN'T TURN? 2) HAVING COMMERCIAL AIRLINERS (WITH 250 PEOPLE AND LIVES AT STAKE!) PASSING WITHIN 1 MI OF EACH OTHER AT 250 KTS WITHOUT BOTH HAVING THE OTHER IN SIGHT IS NOT VERY SMART (WE WERE NEVER EVEN ADVISED OF ACR'S PRESENCE UNTIL WE INQUIRED ABOUT THE ACFT OFF OUR L). THIS '15 DEG COURSE' RULE IS ESPECIALLY DANGEROUS WHEN A SIT LIKE OURS OCCURS (IE, LAX DEPARTING ACFT E, ARRS COMING FROM THE E HEADED INBOUND ON THE RECIPROCAL COURSE OF THE DEPS). CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR IS CONCERNED THAT ACFT ARE FLYING TOO CLOSE TOGETHER. ALL CLRNCS AND SEPARATIONS ARE PROPER, BUT, HE FEELS THAT WITH LARGE ACFT BEING FLOWN, ACFT ARE TOO CLOSE TOGETHER. HE ISN'T CERTAIN THAT OTHER ACFT WILL TURN WHEN SUPPOSED TO, OR THAT A 15 DEG DIVERGENCE IS A GOOD IDEA. HE REALLY WANTS MORE SEPARATION AROUND HIM AND OTHER ACFT. ALTHOUGH THE OTHER ACFT WAS TALKING TO TRACON, EACH ACFT WAS ON A DIFFERENT FREQ, SO THIS RPTR COULD NOT GAIN ANY INFO REGARDING THE OTHER ACFT.

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.