Narrative:

At 300' heading 255 degrees, first vector at 2000' to 180 degrees, second at 3000' to 120 degrees, last clearance before incident at 4000', 'cleared direct woodstown maintain 6000'.' about 5000' while turning east I spotted another aircraft (medium large transport Y) 2 mi ahead at 1000' above. I immediately reduced my climb rate to pass below and behind the other aircraft. About 5500' I was told by departure control or wash center to maintain 5000' (which I did), although I had already altered my flight path so as to pass clear of the other aircraft. Our closest point was about 1/2 mi and 500' altitude difference. Either ATC/departure control cleared both aircraft to the same altitude, or one of the flight crews misunderstood their clearance. There also might have been some confusion on handoff from phl departure control to wash center. I do not know if there were any aircraft with similar names or numbers in the area. Callback conversation with reporter revealed the following: reporter made a report to company concerning this apparent loss of sep. He has not received word yet on the findings of FAA's investigation. He stated that the other aircraft was on the same track as his aircraft and that they were slowly overtaking the preceding aircraft. When asked about his speculation about one of the flight crews taking the wrong altitude, he said that he added that to his report only because that is always a possibility. He still thinks that their clearance was direct ood, maintain 6000'.

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Original NASA ASRS Text

Title: LESS THAN STANDARD SEPARATION WHEN ACR-WDB OVERTAKES ACR-MLG DURING CLIMBOUT.

Narrative: AT 300' HDG 255 DEGS, FIRST VECTOR AT 2000' TO 180 DEGS, SECOND AT 3000' TO 120 DEGS, LAST CLRNC BEFORE INCIDENT AT 4000', 'CLRED DIRECT WOODSTOWN MAINTAIN 6000'.' ABOUT 5000' WHILE TURNING E I SPOTTED ANOTHER ACFT (MLG Y) 2 MI AHEAD AT 1000' ABOVE. I IMMEDIATELY REDUCED MY CLB RATE TO PASS BELOW AND BEHIND THE OTHER ACFT. ABOUT 5500' I WAS TOLD BY DEP CTL OR WASH CENTER TO MAINTAIN 5000' (WHICH I DID), ALTHOUGH I HAD ALREADY ALTERED MY FLT PATH SO AS TO PASS CLR OF THE OTHER ACFT. OUR CLOSEST POINT WAS ABOUT 1/2 MI AND 500' ALT DIFFERENCE. EITHER ATC/DEP CTL CLRED BOTH ACFT TO THE SAME ALT, OR ONE OF THE FLT CREWS MISUNDERSTOOD THEIR CLRNC. THERE ALSO MIGHT HAVE BEEN SOME CONFUSION ON HDOF FROM PHL DEP CTL TO WASH CENTER. I DO NOT KNOW IF THERE WERE ANY ACFT WITH SIMILAR NAMES OR NUMBERS IN THE AREA. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING: RPTR MADE A RPT TO COMPANY CONCERNING THIS APPARENT LOSS OF SEP. HE HAS NOT RECEIVED WORD YET ON THE FINDINGS OF FAA'S INVESTIGATION. HE STATED THAT THE OTHER ACFT WAS ON THE SAME TRACK AS HIS ACFT AND THAT THEY WERE SLOWLY OVERTAKING THE PRECEDING ACFT. WHEN ASKED ABOUT HIS SPECULATION ABOUT ONE OF THE FLT CREWS TAKING THE WRONG ALT, HE SAID THAT HE ADDED THAT TO HIS RPT ONLY BECAUSE THAT IS ALWAYS A POSSIBILITY. HE STILL THINKS THAT THEIR CLRNC WAS DIRECT OOD, MAINTAIN 6000'.

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.