Narrative:

I was being vectored for an lda 18 approach at dca. A runway change was in progress. From the sound of it, the controller was very busy. My mode C was reported intermittent and at times inoperative by ZNY prior to the handoff to dca. At the time of the incident I was given a clearance from 6000-5000'. I began a 500 FPM descent. Due to the runway charge I was reviewing the new approach plate and my first officer had the watch briefly, which is my company procedure. Out of approximately 5600' he saw another air carrier large transport converging from 1-2 O'clock position at what appeared to be a collision course. He took immediate evasive action and informed me at the same time of why and what he was doing. I then took control of my aircraft and didn't change a thing he had done. The other flight then asked approach what my altitude was. The controller responded, 'he's level at 5000'.' I immediately responded 'I am not level at 5000', I am now out of 5400' descending to 5000' and that was very close.' at this point the controller was obviously shaken and on at least 2 occasions called us by the wrong flight #. My feelings are that the controller was too busy, he made an assumption (my altitude) that he shouldn't have, the other flight shouldn't have been that close to me or my flight path in the first place. He had been given a descent from 9000-6000' at approximately the same time I was given a descent from 6000-5000', his descent obviously much faster than mine. I only had 1000' to lose. I've been an airline pilot for over 20 yrs and I believe the ATC system in many areas in our country is stretched to the limit of acceptable safety.

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Original NASA ASRS Text

Title: LOSS OF SEPARATION WHEN LGT DESCENDED AT A VERY RAPID RATE AFTER REPORTER HAD BEEN CLEARED TO 5000'.

Narrative: I WAS BEING VECTORED FOR AN LDA 18 APCH AT DCA. A RWY CHANGE WAS IN PROGRESS. FROM THE SOUND OF IT, THE CTLR WAS VERY BUSY. MY MODE C WAS RPTED INTERMITTENT AND AT TIMES INOP BY ZNY PRIOR TO THE HDOF TO DCA. AT THE TIME OF THE INCIDENT I WAS GIVEN A CLRNC FROM 6000-5000'. I BEGAN A 500 FPM DSCNT. DUE TO THE RWY CHARGE I WAS REVIEWING THE NEW APCH PLATE AND MY F/O HAD THE WATCH BRIEFLY, WHICH IS MY COMPANY PROC. OUT OF APPROX 5600' HE SAW ANOTHER ACR LGT CONVERGING FROM 1-2 O'CLOCK POS AT WHAT APPEARED TO BE A COLLISION COURSE. HE TOOK IMMEDIATE EVASIVE ACTION AND INFORMED ME AT THE SAME TIME OF WHY AND WHAT HE WAS DOING. I THEN TOOK CTL OF MY ACFT AND DIDN'T CHANGE A THING HE HAD DONE. THE OTHER FLT THEN ASKED APCH WHAT MY ALT WAS. THE CTLR RESPONDED, 'HE'S LEVEL AT 5000'.' I IMMEDIATELY RESPONDED 'I AM NOT LEVEL AT 5000', I AM NOW OUT OF 5400' DSNDING TO 5000' AND THAT WAS VERY CLOSE.' AT THIS POINT THE CTLR WAS OBVIOUSLY SHAKEN AND ON AT LEAST 2 OCCASIONS CALLED US BY THE WRONG FLT #. MY FEELINGS ARE THAT THE CTLR WAS TOO BUSY, HE MADE AN ASSUMPTION (MY ALT) THAT HE SHOULDN'T HAVE, THE OTHER FLT SHOULDN'T HAVE BEEN THAT CLOSE TO ME OR MY FLT PATH IN THE FIRST PLACE. HE HAD BEEN GIVEN A DSCNT FROM 9000-6000' AT APPROX THE SAME TIME I WAS GIVEN A DSCNT FROM 6000-5000', HIS DSCNT OBVIOUSLY MUCH FASTER THAN MINE. I ONLY HAD 1000' TO LOSE. I'VE BEEN AN AIRLINE PLT FOR OVER 20 YRS AND I BELIEVE THE ATC SYS IN MANY AREAS IN OUR COUNTRY IS STRETCHED TO THE LIMIT OF ACCEPTABLE SAFETY.

Data retrieved from NASA's ASRS site as of August 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.