ZBW controller experienced operational error because of readback error.

Attributes
ACN	609238
Time
Date	200402
Day	Tue
Local Time Of Day	1201 To 1800
Place
Locale Reference	navaid : baf.vortac
State Reference	MA
Altitude	msl bound lower : 15000 msl bound upper : 16000
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zbw.artcc
Operator	common carrier : air carrier
Make Model Name	B767 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Navigation In Use	other
Flight Phase	descent : intermediate altitude
Route In Use	arrival : on vectors
Flight Plan	IFR
Aircraft 2
Controlling Facilities	artcc : zbw.artcc
Operator	general aviation : corporate
Make Model Name	Challenger CL600
Operating Under FAR Part	Part 91
Flight Phase	cruise : level
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Experience	controller radar : 2
ASRS Report	609238
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Events
Anomaly	conflict : airborne critical non adherence : required legal separation
Independent Detector	atc equipment : conflict alert other controllera
Resolutory Action	controller : issued alert controller : issued new clearance
Consequence	faa : investigated
Miss Distance	horizontal : 4500 vertical : 300
Supplementary
Problem Areas	ATC Human Performance
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

Aircraft issued a clearance to cross 15 mi east of baf at 16000 ft. He read it back 'cross 15 mi east of baf at 15000 ft.' CL60 was at 15000 ft the same direction. Before I could stop the B767 from descending he was below 15500 ft. The position was combined during a busy period.

Original NASA ASRS Text

Title: ZBW CTLR EXPERIENCED OPERROR BECAUSE OF READBACK ERROR.

Narrative: ACFT ISSUED A CLRNC TO CROSS 15 MI E OF BAF AT 16000 FT. HE READ IT BACK 'CROSS 15 MI E OF BAF AT 15000 FT.' CL60 WAS AT 15000 FT THE SAME DIRECTION. BEFORE I COULD STOP THE B767 FROM DSNDING HE WAS BELOW 15500 FT. THE POS WAS COMBINED DURING A BUSY PERIOD.

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.