Narrative:

Descending into the palm springs area, I was the PNF and just got handed off from ZLA to psp approach at around 15000 ft, maybe slightly lower. ZLA gave us a descent instruction of pilot's discretion to 11000 ft MSL. When I checked in with psp approach, I stated out altitude and discretion to 11000 ft MSL. The controller responded in the affirmative. At this point, I noticed on our TCASII a target at the 12 O'clock position and 10-15 mi out. It was several thousand ft below us and climbing. I had visual contact with the traffic and assumed that the controller had been handling this aircraft also. This other target was an air carrier MD80 climbing out of palm springs. I assumed he was going to level shy of our 11000 ft altitude. The air carrier jet also assumed we were leveling above his altitude. When I realized that the other traffic was not leveling and we were closing quickly on a collision course, it was (the other traffic) within 3 mi. I told the captain immediately to change course just as the controller instructed us to turn immediately to the left. The airplane was still on autoplt and was making a smooth and slow turn to the left when I stated again, 'turn now, turn.' the captain removed autoplt control and banked the aircraft into a 50-55 degree turn while slowing the descent. At this point, I lost visual contact with the jet due to the steep bank. We got the traffic alert on the TCASII and as I watched it, it displayed a -7 symbol, which is indicative of a 700 ft separation. The controller said he had no idea what had happened, but we gave him our last altitude and called him from the ground phone. It turns out that the controller claims that there was a glitch in the problematic psp radar. In light of this incident, I now keep a much more vigilant watch of the traffic around me, and query ATC when I am unsure of our 'traffic.' in addition, I am more familiar with the fact that ATC is not perfect, but tries its best to separate traffic.

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Original NASA ASRS Text

Title: AN EMB120 FO, THE PNF, MAINTAINED EXCELLENT SITUATIONAL AWARENESS AND WAS ABLE TO VECTOR HIS CAPT AROUND A POTENTIAL NMAC ACFT WHEN PSP ATC WAS UNABLE TO HELP.

Narrative: DSNDING INTO THE PALM SPRINGS AREA, I WAS THE PNF AND JUST GOT HANDED OFF FROM ZLA TO PSP APCH AT AROUND 15000 FT, MAYBE SLIGHTLY LOWER. ZLA GAVE US A DSCNT INSTRUCTION OF PLT'S DISCRETION TO 11000 FT MSL. WHEN I CHKED IN WITH PSP APCH, I STATED OUT ALT AND DISCRETION TO 11000 FT MSL. THE CTLR RESPONDED IN THE AFFIRMATIVE. AT THIS POINT, I NOTICED ON OUR TCASII A TARGET AT THE 12 O'CLOCK POS AND 10-15 MI OUT. IT WAS SEVERAL THOUSAND FT BELOW US AND CLBING. I HAD VISUAL CONTACT WITH THE TFC AND ASSUMED THAT THE CTLR HAD BEEN HANDLING THIS ACFT ALSO. THIS OTHER TARGET WAS AN ACR MD80 CLBING OUT OF PALM SPRINGS. I ASSUMED HE WAS GOING TO LEVEL SHY OF OUR 11000 FT ALT. THE ACR JET ALSO ASSUMED WE WERE LEVELING ABOVE HIS ALT. WHEN I REALIZED THAT THE OTHER TFC WAS NOT LEVELING AND WE WERE CLOSING QUICKLY ON A COLLISION COURSE, IT WAS (THE OTHER TFC) WITHIN 3 MI. I TOLD THE CAPT IMMEDIATELY TO CHANGE COURSE JUST AS THE CTLR INSTRUCTED US TO TURN IMMEDIATELY TO THE L. THE AIRPLANE WAS STILL ON AUTOPLT AND WAS MAKING A SMOOTH AND SLOW TURN TO THE L WHEN I STATED AGAIN, 'TURN NOW, TURN.' THE CAPT REMOVED AUTOPLT CTL AND BANKED THE ACFT INTO A 50-55 DEG TURN WHILE SLOWING THE DSCNT. AT THIS POINT, I LOST VISUAL CONTACT WITH THE JET DUE TO THE STEEP BANK. WE GOT THE TFC ALERT ON THE TCASII AND AS I WATCHED IT, IT DISPLAYED A -7 SYMBOL, WHICH IS INDICATIVE OF A 700 FT SEPARATION. THE CTLR SAID HE HAD NO IDEA WHAT HAD HAPPENED, BUT WE GAVE HIM OUR LAST ALT AND CALLED HIM FROM THE GND PHONE. IT TURNS OUT THAT THE CTLR CLAIMS THAT THERE WAS A GLITCH IN THE PROBLEMATIC PSP RADAR. IN LIGHT OF THIS INCIDENT, I NOW KEEP A MUCH MORE VIGILANT WATCH OF THE TFC AROUND ME, AND QUERY ATC WHEN I AM UNSURE OF OUR 'TFC.' IN ADDITION, I AM MORE FAMILIAR WITH THE FACT THAT ATC IS NOT PERFECT, BUT TRIES ITS BEST TO SEPARATE TFC.

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.