Narrative:

ATC facility: dulles TRACON. Location: 20 NM west aml VORTAC/iad. I was PF and making a final PA to passenger when first officer received query and clearance to maintain visual separation from a B757 at 14000 ft MSL. We were at 15000 ft MSL. He stated traffic in sight and we were given clearance to expedite descent through his altitude down to 12000 ft. I got off the PA, having heard a descent clearance, but I did not know the specifics. First officer advised we needed to hurry down so I started a smooth but aggressive descent to get through the traffic altitude. Well into the descent and at least 4000 FPM, got a TCASII advisory to climb. Traffic at that point was in sight and in my judgement it was a faster and safer maneuver to continue the aggressive descent through his altitude and out of the way. Apparently, the TCASII commanded him to descend also when I did not follow my unit's advisory and that complicated the evasion. I continued down to assigned 12000 ft altitude quickly and smoothly without incident. Closest point of approach probably 4 mi but at common altitude no closer than 6 mi. Lessons learned are: consideration on my part to making my personal sterile period FL180 and below in busy terminal areas. Lesson #2: both pilots should always coordinate and agree before accepting visual separation clearance. Lesson #3 and most important --IFR flight plan. Let ATC controllers separate, let pilots fly. We all have best intentions to help the system work, but if oftentimes winds up helping no one -- controller or pilot -- to cut corners on the system. Supplemental information from acn 353243: we were at 15000 ft. Traffic was at 14000 ft. Approach called traffic at 2 O'clock and 20 mi.

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Original NASA ASRS Text

Title: OPPOSITE DIRECTION TFC. A VISUAL DSCNT THROUGH OCCUPIED ALT IS GIVEN BY IAD TRACON. A NEAR POTENTIAL CONFLICT IS SENSED BY TCASII RA. PIC OF ACFT X FAILS TO HEED THE RA COMMAND AND CONTINUES DSCNT USING VISUAL FLC JUDGEMENT OF TFC SPACING. PIC ACFT X CITES LACK OF SITUATIONAL AWARENESS RELATED TO SPECIFICS OF DSCNT CLRNC.

Narrative: ATC FACILITY: DULLES TRACON. LOCATION: 20 NM W AML VORTAC/IAD. I WAS PF AND MAKING A FINAL PA TO PAX WHEN FO RECEIVED QUERY AND CLRNC TO MAINTAIN VISUAL SEPARATION FROM A B757 AT 14000 FT MSL. WE WERE AT 15000 FT MSL. HE STATED TFC IN SIGHT AND WE WERE GIVEN CLRNC TO EXPEDITE DSCNT THROUGH HIS ALT DOWN TO 12000 FT. I GOT OFF THE PA, HAVING HEARD A DSCNT CLRNC, BUT I DID NOT KNOW THE SPECIFICS. FO ADVISED WE NEEDED TO HURRY DOWN SO I STARTED A SMOOTH BUT AGGRESSIVE DSCNT TO GET THROUGH THE TFC ALT. WELL INTO THE DSCNT AND AT LEAST 4000 FPM, GOT A TCASII ADVISORY TO CLB. TFC AT THAT POINT WAS IN SIGHT AND IN MY JUDGEMENT IT WAS A FASTER AND SAFER MANEUVER TO CONTINUE THE AGGRESSIVE DSCNT THROUGH HIS ALT AND OUT OF THE WAY. APPARENTLY, THE TCASII COMMANDED HIM TO DSND ALSO WHEN I DID NOT FOLLOW MY UNIT'S ADVISORY AND THAT COMPLICATED THE EVASION. I CONTINUED DOWN TO ASSIGNED 12000 FT ALT QUICKLY AND SMOOTHLY WITHOUT INCIDENT. CLOSEST POINT OF APCH PROBABLY 4 MI BUT AT COMMON ALT NO CLOSER THAN 6 MI. LESSONS LEARNED ARE: CONSIDERATION ON MY PART TO MAKING MY PERSONAL STERILE PERIOD FL180 AND BELOW IN BUSY TERMINAL AREAS. LESSON #2: BOTH PLTS SHOULD ALWAYS COORDINATE AND AGREE BEFORE ACCEPTING VISUAL SEPARATION CLRNC. LESSON #3 AND MOST IMPORTANT --IFR FLT PLAN. LET ATC CTLRS SEPARATE, LET PLTS FLY. WE ALL HAVE BEST INTENTIONS TO HELP THE SYS WORK, BUT IF OFTENTIMES WINDS UP HELPING NO ONE -- CTLR OR PLT -- TO CUT CORNERS ON THE SYS. SUPPLEMENTAL INFO FROM ACN 353243: WE WERE AT 15000 FT. TFC WAS AT 14000 FT. APCH CALLED TFC AT 2 O'CLOCK AND 20 MI.

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.