Narrative:

While under control of bdl approach on an assigned heading of 030 at 5000 ft, I noticed a possible conflicting target on TCASII screen at 1500 ft below our aircraft and approximately 2-3 NM at 12 O'clock. The target was shown on TCASII to be climbing, and not diverging from our course. As we continued under control of ATC, the intruder continued to climb until the TCASII issued a TA. Both the copilot and myself were attempting to locate the target visually, but could not see it. As the intruder continued to climb, our TCASII issued an RA and ordered a climb. As we initiated a climb, we spotted the target just below and right of our aircraft on the same heading and climbing. We climbed to approximately 5800 ft as commanded by our TCASII and returned to 5000 ft upon clearing the other aircraft. I advised atl when we started our climb, and again called when returning to our assigned altitude. No traffic callouts were received from ATC, and no acknowledgement from them was received after my transmissions. The controller was busy handling arriving aircraft, plus numerous calls from VFR aircraft requesting radar advisories caused extensive frequency congestion. These factors, plus the intruding aircraft's climb from a position below us, led to a near miss. TCASII was very helpful in avoiding a collision, and points out the need for all aircraft to have altitude encoding transponders in the congested airspace of the eastern us also the requirement to visually avoid VFR traffic while still being required to fly specified altitudes and airspds near an airport is unrealistic in the high density areas of the northeast us

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Original NASA ASRS Text

Title: MLG AT STEP DOWN DSCNT ALT FOR APCH HAS TCASII RA. CLBS.

Narrative: WHILE UNDER CTL OF BDL APCH ON AN ASSIGNED HDG OF 030 AT 5000 FT, I NOTICED A POSSIBLE CONFLICTING TARGET ON TCASII SCREEN AT 1500 FT BELOW OUR ACFT AND APPROX 2-3 NM AT 12 O'CLOCK. THE TARGET WAS SHOWN ON TCASII TO BE CLBING, AND NOT DIVERGING FROM OUR COURSE. AS WE CONTINUED UNDER CTL OF ATC, THE INTRUDER CONTINUED TO CLB UNTIL THE TCASII ISSUED A TA. BOTH THE COPLT AND MYSELF WERE ATTEMPTING TO LOCATE THE TARGET VISUALLY, BUT COULD NOT SEE IT. AS THE INTRUDER CONTINUED TO CLB, OUR TCASII ISSUED AN RA AND ORDERED A CLB. AS WE INITIATED A CLB, WE SPOTTED THE TARGET JUST BELOW AND R OF OUR ACFT ON THE SAME HDG AND CLBING. WE CLBED TO APPROX 5800 FT AS COMMANDED BY OUR TCASII AND RETURNED TO 5000 FT UPON CLRING THE OTHER ACFT. I ADVISED ATL WHEN WE STARTED OUR CLB, AND AGAIN CALLED WHEN RETURNING TO OUR ASSIGNED ALT. NO TFC CALLOUTS WERE RECEIVED FROM ATC, AND NO ACKNOWLEDGEMENT FROM THEM WAS RECEIVED AFTER MY TRANSMISSIONS. THE CTLR WAS BUSY HANDLING ARRIVING ACFT, PLUS NUMEROUS CALLS FROM VFR ACFT REQUESTING RADAR ADVISORIES CAUSED EXTENSIVE FREQ CONGESTION. THESE FACTORS, PLUS THE INTRUDING ACFT'S CLB FROM A POS BELOW US, LED TO A NEAR MISS. TCASII WAS VERY HELPFUL IN AVOIDING A COLLISION, AND POINTS OUT THE NEED FOR ALL ACFT TO HAVE ALT ENCODING TRANSPONDERS IN THE CONGESTED AIRSPACE OF THE EASTERN U.S. ALSO THE REQUIREMENT TO VISUALLY AVOID VFR TFC WHILE STILL BEING REQUIRED TO FLY SPECIFIED ALTS AND AIRSPDS NEAR AN ARPT IS UNREALISTIC IN THE HIGH DENSITY AREAS OF THE NE U.S.

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.