Narrative:

Departed ont via the pomona 2 departure, gmn transition. Our original cleared altitude was 12000'. As we were cleared for takeoff we were reclred to maintain 4000'. When we switched over to ont departure on 125.5 there was so much frequency congestion involving light aircraft requesting arsa clearance, etc, that we were unable to complete a radio call after repeated attempts. We were at 4000' headed straight for terrain in excess of 8000', past karyn intersection with still no radio contact due to frequency congestion. I decided we had to turn west to avoid the terrain. At 4000', just prior to turning, the first officer who was flying the plane noticed a light twin at 2 O'clock turning and descending right for us at an estimated 300' or less sep with a closure rate. We turned left and descended to about 3500' to avoid the twin. We then climbed back to 4000', heading west, when we finally made radio contact with ont departure. ZLA later apologized for the handling after we were cleared to climb and on course. Besides the obvious problems and possible situations created here, I believe a possible solution would be to amend the pomona 2 SID to include host communications procedures as so many other SID's do, particularly where high terrain is involved. This SID currently only direct minimum climb rates. Also, I don't think we should have been cleared to 4000', or maybe I should not have accepted the clearance. Even though the WX was unlimited visibly and no clouds, and we weren't about to hit the terrain because we could see it, you can see how a situation can rapidly deteriorate in a high density airspace environment surrounded by high terrain.

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Original NASA ASRS Text

Title: CLOSE PROX ACR-MLG GA-SMA. REPORTER ALSO RECOMMENDS LOST COM PROC BE INCLUDED ON ONT SID.

Narrative: DEPARTED ONT VIA THE POMONA 2 DEP, GMN TRANSITION. OUR ORIGINAL CLRED ALT WAS 12000'. AS WE WERE CLRED FOR TKOF WE WERE RECLRED TO MAINTAIN 4000'. WHEN WE SWITCHED OVER TO ONT DEP ON 125.5 THERE WAS SO MUCH FREQ CONGESTION INVOLVING LIGHT ACFT REQUESTING ARSA CLRNC, ETC, THAT WE WERE UNABLE TO COMPLETE A RADIO CALL AFTER REPEATED ATTEMPTS. WE WERE AT 4000' HEADED STRAIGHT FOR TERRAIN IN EXCESS OF 8000', PAST KARYN INTXN WITH STILL NO RADIO CONTACT DUE TO FREQ CONGESTION. I DECIDED WE HAD TO TURN W TO AVOID THE TERRAIN. AT 4000', JUST PRIOR TO TURNING, THE F/O WHO WAS FLYING THE PLANE NOTICED A LIGHT TWIN AT 2 O'CLOCK TURNING AND DSNDING RIGHT FOR US AT AN ESTIMATED 300' OR LESS SEP WITH A CLOSURE RATE. WE TURNED LEFT AND DSNDED TO ABOUT 3500' TO AVOID THE TWIN. WE THEN CLBED BACK TO 4000', HDG W, WHEN WE FINALLY MADE RADIO CONTACT WITH ONT DEP. ZLA LATER APOLOGIZED FOR THE HANDLING AFTER WE WERE CLRED TO CLB AND ON COURSE. BESIDES THE OBVIOUS PROBS AND POSSIBLE SITUATIONS CREATED HERE, I BELIEVE A POSSIBLE SOLUTION WOULD BE TO AMEND THE POMONA 2 SID TO INCLUDE HOST COMS PROCS AS SO MANY OTHER SID'S DO, PARTICULARLY WHERE HIGH TERRAIN IS INVOLVED. THIS SID CURRENTLY ONLY DIRECT MINIMUM CLB RATES. ALSO, I DON'T THINK WE SHOULD HAVE BEEN CLRED TO 4000', OR MAYBE I SHOULD NOT HAVE ACCEPTED THE CLRNC. EVEN THOUGH THE WX WAS UNLIMITED VISIBLY AND NO CLOUDS, AND WE WEREN'T ABOUT TO HIT THE TERRAIN BECAUSE WE COULD SEE IT, YOU CAN SEE HOW A SITUATION CAN RAPIDLY DETERIORATE IN A HIGH DENSITY AIRSPACE ENVIRONMENT SURROUNDED BY HIGH TERRAIN.

Data retrieved from NASA's ASRS site as of August 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.