ZBW experienced loss of separation with C550 and BE36 at 6000 ft.

Attributes
ACN	593592
Time
Date	200309
Day	Tue
Local Time Of Day	1801 To 2400
Place
State Reference	MA
Altitude	msl single value : 6000
Environment
Flight Conditions	VMC
Light	Dusk
Aircraft 1
Controlling Facilities	artcc : zbw.artcc
Operator	general aviation : corporate
Make Model Name	Citation II S2/Bravo
Operating Under FAR Part	Part 91
Flight Phase	descent : intermediate altitude
Flight Plan	IFR
Aircraft 2
Controlling Facilities	artcc : zbw.artcc
Operator	general aviation : personal
Make Model Name	Bonanza 36
Operating Under FAR Part	Part 91
Flight Phase	cruise : level
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar controller : military
Experience	controller military : 7 controller radar : 19
ASRS Report	593592
Person 2
Affiliation	company : corporate
Function	flight crew : captain oversight : pic
Events
Anomaly	conflict : airborne less severe non adherence : required legal separation
Independent Detector	atc equipment : conflict alert other controllera
Resolutory Action	none taken : insufficient time none taken : detected after the fact
Consequence	faa : investigated
Miss Distance	horizontal : 27600 vertical : 400
Supplementary
Problem Areas	ATC Human Performance
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

My sector was very busy. I was told it was going 'red.' numerous aircraft were inbound to bos, bed and mht with overtaking sits. The C550 was given a descent to 6000 ft. It appeared (using vector lines) that it would pass behind the aircraft at 7000 ft. Due to data block congestion (there were approximately 20 data blocks) I did not notice the aircraft descending to 6000 ft flashing. The aircraft at 7000 ft was already flashing with a VFR aircraft at 6500 ft.

Original NASA ASRS Text

Title: ZBW EXPERIENCED LOSS OF SEPARATION WITH C550 AND BE36 AT 6000 FT.

Narrative: MY SECTOR WAS VERY BUSY. I WAS TOLD IT WAS GOING 'RED.' NUMEROUS ACFT WERE INBOUND TO BOS, BED AND MHT WITH OVERTAKING SITS. THE C550 WAS GIVEN A DSCNT TO 6000 FT. IT APPEARED (USING VECTOR LINES) THAT IT WOULD PASS BEHIND THE ACFT AT 7000 FT. DUE TO DATA BLOCK CONGESTION (THERE WERE APPROX 20 DATA BLOCKS) I DID NOT NOTICE THE ACFT DSNDING TO 6000 FT FLASHING. THE ACFT AT 7000 FT WAS ALREADY FLASHING WITH A VFR ACFT AT 6500 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.