ZDC issues conflicting altitude to BE20 and C750. C750 initiated TCASII maneuver.

Attributes
ACN	504040
Time
Date	200102
Day	Tue
Local Time Of Day	1201 To 1800
Place
Locale Reference	navaid : dqo.vortac
State Reference	DE
Altitude	msl bound lower : 11000 msl bound upper : 12000
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	artcc : zdc.artcc
Operator	general aviation : personal
Make Model Name	Super King Air 200 HDC
Operating Under FAR Part	Part 91
Flight Phase	cruise : level descent : approach descent : intermediate altitude
Route In Use	arrival star : ns enroute airway : v214.airway
Flight Plan	IFR
Aircraft 2
Controlling Facilities	artcc : zdc.artcc
Operator	general aviation : corporate
Make Model Name	Citation X
Operating Under FAR Part	Part 91
Flight Phase	cruise : enroute altitude change descent : vacating altitude descent : approach
Route In Use	arrival star : n/s enroute airway : v214.airway
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : handoff position
Qualification	controller : radar pilot : private
Experience	controller radar : 15 flight time total : 180
ASRS Report	504040
Person 2
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Events
Anomaly	conflict : airborne critical non adherence : published procedure non adherence : required legal separation
Independent Detector	atc equipment : conflict alert atc equipment other atc equipment : radar aircraft equipment : tcas other controllera other flight crewa
Resolutory Action	controller : issued new clearance controller : separated traffic
Miss Distance	horizontal : 4800 vertical : 400
Supplementary
Problem Areas	ATC Human Performance
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

BE20 was at 11000 ft at stefe intersection with C750 cleared to 11000 ft also, but data block indicated 12000 ft. Pilot climbed back to 12000 ft when radar controller observed mode C drop below 12000 ft. Radar controller meant to issue C750 to cross stefe at 12000 ft, but issued 11000 ft instead.

Original NASA ASRS Text

Title: ZDC ISSUES CONFLICTING ALT TO BE20 AND C750. C750 INITIATED TCASII MANEUVER.

Narrative: BE20 WAS AT 11000 FT AT STEFE INTXN WITH C750 CLRED TO 11000 FT ALSO, BUT DATA BLOCK INDICATED 12000 FT. PLT CLBED BACK TO 12000 FT WHEN RADAR CTLR OBSERVED MODE C DROP BELOW 12000 FT. RADAR CTLR MEANT TO ISSUE C750 TO CROSS STEFE AT 12000 FT, BUT ISSUED 11000 FT INSTEAD.

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.