Narrative:

Flying flight to den, cleared prado 5 departure, unrestr climb to 7000 ft direct pdz. Several mi north of pdz VOR, we got an RA 'reduce climb,' intruder 10 O'clock at 5500 ft MSL. We were climbing out of 4500 ft MSL. Socal approach then warned us on frequency 135.4 of intruder, suggested leveloff at 5000 ft MSL. It was wbound, a single engine cessna level at 5500 ft MSL (wrong altitude for direction of flight). We passed 500 ft below cessna due to reduced climb. Picked up intruder aircraft visually immediately after TCASII RA. TCASII picked it up first and possibly prevented a midair. I am now a believer. Several mins later, when above FL180, I called approach back. By now we were talking to ZLA. Just wanted to verify that other aircraft was not in class B airspace. Sure enough, he was legally ok to fly where he was without being in communication, though he was at wrong altitude for direction of flight, and was not climbing or descending. Legal, but not prudent. I started out in GA so I can relate and am well aware that some GA pilots just don't like to talk on the radio if they don't have to. If we had not leveled off it would have been a midair or an extremely close call.

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Original NASA ASRS Text

Title: A DEP, CLBING B737-300, HAS AN NMAC WITH A CESSNA TYPE ACFT FLYING OPPOSITE DIRECTION WITH NORAC TFC 3 MI NW OF PDZ, CA.

Narrative: FLYING FLT TO DEN, CLRED PRADO 5 DEP, UNRESTR CLB TO 7000 FT DIRECT PDZ. SEVERAL MI N OF PDZ VOR, WE GOT AN RA 'REDUCE CLB,' INTRUDER 10 O'CLOCK AT 5500 FT MSL. WE WERE CLBING OUT OF 4500 FT MSL. SOCAL APCH THEN WARNED US ON FREQ 135.4 OF INTRUDER, SUGGESTED LEVELOFF AT 5000 FT MSL. IT WAS WBOUND, A SINGLE ENG CESSNA LEVEL AT 5500 FT MSL (WRONG ALT FOR DIRECTION OF FLT). WE PASSED 500 FT BELOW CESSNA DUE TO REDUCED CLB. PICKED UP INTRUDER ACFT VISUALLY IMMEDIATELY AFTER TCASII RA. TCASII PICKED IT UP FIRST AND POSSIBLY PREVENTED A MIDAIR. I AM NOW A BELIEVER. SEVERAL MINS LATER, WHEN ABOVE FL180, I CALLED APCH BACK. BY NOW WE WERE TALKING TO ZLA. JUST WANTED TO VERIFY THAT OTHER ACFT WAS NOT IN CLASS B AIRSPACE. SURE ENOUGH, HE WAS LEGALLY OK TO FLY WHERE HE WAS WITHOUT BEING IN COM, THOUGH HE WAS AT WRONG ALT FOR DIRECTION OF FLT, AND WAS NOT CLBING OR DSNDING. LEGAL, BUT NOT PRUDENT. I STARTED OUT IN GA SO I CAN RELATE AND AM WELL AWARE THAT SOME GA PLTS JUST DON'T LIKE TO TALK ON THE RADIO IF THEY DON'T HAVE TO. IF WE HAD NOT LEVELED OFF IT WOULD HAVE BEEN A MIDAIR OR AN EXTREMELY CLOSE CALL.

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.