Narrative:

On radar vectors for runway 4R ewr left base, cleared to descend from 4000 ft to 2000 ft with no speeds assigned. At about 3500 ft, began to decelerate. With no prior notice, ATC informed us there was a cheyenne turboprop at same altitude in opposing direction. ATC asked us to immediately increase our descent rate at which point I did, using a higher vertical speed rate. Within a few seconds of this, we got a TCASII TA showing conflict traffic at same altitude and closing. A few seconds later, TCASII issued a 'descend now' RA we still could not visually see cheyenne. I complied with RA. Immediately by disconnecting autoplt and aggressively pushing down on stick. First officer visually saw cheyenne during the descent push and said separation was possibly as close as 1/2 mi. Cheyenne passed off to our upper right received 'clear of conflict' and proceeded to a normal landing. Isn't this a class B airspace? Supplemental information from acn 592046: on base leg we were cleared to descend from 5000 ft to 3000 ft. During the descent, at approximately 3500 ft, ATC advised of a GA aircraft (cheyenne) at 2 O'clock position, 3500 ft. We immediately received an RA on our TCASII and the captain accelerated the descent rate. The aircraft was sited approximately 1/2 - 3/4 mi separation, same altitude. Aircraft passed to the right. When originally cleared to descend, there was no speed assigned or traffic mentioned. From the time ATC mentioned the traffic to the time of the RA was only 2-3 seconds.

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Original NASA ASRS Text

Title: SYS ERROR OCCURS WHEN THERE IS A CRITICAL AIRBORNE CONFLICT BTWN AN INBOUND DSNDING A320 ON A L BASE FOR RWY 4R AND A LEVEL NWBOUND VFR CHEYENNE AT 3500 FT, 4 NM W OF EWR, NJ.

Narrative: ON RADAR VECTORS FOR RWY 4R EWR L BASE, CLRED TO DSND FROM 4000 FT TO 2000 FT WITH NO SPDS ASSIGNED. AT ABOUT 3500 FT, BEGAN TO DECELERATE. WITH NO PRIOR NOTICE, ATC INFORMED US THERE WAS A CHEYENNE TURBOPROP AT SAME ALT IN OPPOSING DIRECTION. ATC ASKED US TO IMMEDIATELY INCREASE OUR DSCNT RATE AT WHICH POINT I DID, USING A HIGHER VERT SPD RATE. WITHIN A FEW SECONDS OF THIS, WE GOT A TCASII TA SHOWING CONFLICT TFC AT SAME ALT AND CLOSING. A FEW SECONDS LATER, TCASII ISSUED A 'DSND NOW' RA WE STILL COULD NOT VISUALLY SEE CHEYENNE. I COMPLIED WITH RA. IMMEDIATELY BY DISCONNECTING AUTOPLT AND AGGRESSIVELY PUSHING DOWN ON STICK. FO VISUALLY SAW CHEYENNE DURING THE DSCNT PUSH AND SAID SEPARATION WAS POSSIBLY AS CLOSE AS 1/2 MI. CHEYENNE PASSED OFF TO OUR UPPER R RECEIVED 'CLR OF CONFLICT' AND PROCEEDED TO A NORMAL LNDG. ISN'T THIS A CLASS B AIRSPACE? SUPPLEMENTAL INFO FROM ACN 592046: ON BASE LEG WE WERE CLRED TO DSND FROM 5000 FT TO 3000 FT. DURING THE DSCNT, AT APPROX 3500 FT, ATC ADVISED OF A GA ACFT (CHEYENNE) AT 2 O'CLOCK POS, 3500 FT. WE IMMEDIATELY RECEIVED AN RA ON OUR TCASII AND THE CAPT ACCELERATED THE DSCNT RATE. THE ACFT WAS SITED APPROX 1/2 - 3/4 MI SEPARATION, SAME ALT. ACFT PASSED TO THE R. WHEN ORIGINALLY CLRED TO DSND, THERE WAS NO SPD ASSIGNED OR TFC MENTIONED. FROM THE TIME ATC MENTIONED THE TFC TO THE TIME OF THE RA WAS ONLY 2-3 SECONDS.

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.