Narrative:

Air carrier X departed runway 9L. The top of my airspace is 10000 ft. I climbed air carrier X to 8000 ft because I took a pointout of another aircraft (overflt to lga) at 9000 ft. I became involved with a routing change to another aircraft and did not notice air carrier X had no transponder. The controller working the overflt to lga descended aircraft Y from 9000 ft to 7000 ft. At that time air carrier X reported to me he was level at 8000 ft. (I imagine the pilot suspected I forgot about him, which I had.) I asked air carrier X his position and his transponder came on at that time, in proximity to lga overflt Y descending to 7000 ft -- who at that time was behind air carrier X.

Google
 

Original NASA ASRS Text

Title: A DEP CTLR EXPERIENCES LOSS OF SEPARATION BTWN HIS DEP B737 FLT X, AND AN OVERFLT ACFT Y PROCEEDING N THROUGH THE CLASS B AIRSPACE 20 MI E OF PHL, PA.

Narrative: ACR X DEPARTED RWY 9L. THE TOP OF MY AIRSPACE IS 10000 FT. I CLBED ACR X TO 8000 FT BECAUSE I TOOK A POINTOUT OF ANOTHER ACFT (OVERFLT TO LGA) AT 9000 FT. I BECAME INVOLVED WITH A ROUTING CHANGE TO ANOTHER ACFT AND DID NOT NOTICE ACR X HAD NO XPONDER. THE CTLR WORKING THE OVERFLT TO LGA DSNDED ACFT Y FROM 9000 FT TO 7000 FT. AT THAT TIME ACR X RPTED TO ME HE WAS LEVEL AT 8000 FT. (I IMAGINE THE PLT SUSPECTED I FORGOT ABOUT HIM, WHICH I HAD.) I ASKED ACR X HIS POS AND HIS XPONDER CAME ON AT THAT TIME, IN PROX TO LGA OVERFLT Y DSNDING TO 7000 FT -- WHO AT THAT TIME WAS BEHIND ACR X.

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.