Narrative:

P210 departed runway 1 VFR. Called for IFR clearance in the air. I gave the aircraft a transponder code and radar idented him. I gave the aircraft clearance to destination and cleared to 4000 ft. C182 was at 5000 ft eastbound. I called traffic to the P210 twice and informed him I would have higher when he cleared traffic. When the targets merged, I lost mode C on P210. When they cleared each other, his mode C showed 5400 ft. I asked his altitude and informed him his clearance limit was 4000 ft.

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Original NASA ASRS Text

Title: ZDC CTLR RPTED PLTDEV WHEN IFR P210 CLBED THROUGH ASSIGNED ALT CONFLICTING WITH A C182 ASSIGNED AN ALT 1000 FT ABOVE THE P210.

Narrative: P210 DEPARTED RWY 1 VFR. CALLED FOR IFR CLRNC IN THE AIR. I GAVE THE ACFT A XPONDER CODE AND RADAR IDENTED HIM. I GAVE THE ACFT CLRNC TO DEST AND CLRED TO 4000 FT. C182 WAS AT 5000 FT EBOUND. I CALLED TFC TO THE P210 TWICE AND INFORMED HIM I WOULD HAVE HIGHER WHEN HE CLRED TFC. WHEN THE TARGETS MERGED, I LOST MODE C ON P210. WHEN THEY CLRED EACH OTHER, HIS MODE C SHOWED 5400 FT. I ASKED HIS ALT AND INFORMED HIM HIS CLRNC LIMIT WAS 4000 FT.

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.