Medium large transport has TCASII warning on descent.

Attributes
ACN	256990
Time
Date	199310
Day	Fri
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : orw
State Reference	CT
Altitude	msl bound lower : 11000 msl bound upper : 12500
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tower : den
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Navigation In Use	Other Other
Flight Phase	descent other
Route In Use	enroute : on vectors enroute airway : zbw
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	Light Transport, Low Wing, 2 Turboprop Eng
Flight Phase	cruise other
Route In Use	enroute : direct
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 150 flight time total : 15000 flight time type : 3000
ASRS Report	256990
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument pilot : atp
Events
Anomaly	conflict : airborne less severe non adherence : clearance other anomaly other other spatial deviation
Independent Detector	aircraft equipment other aircraft equipment : unspecified
Resolutory Action	flight crew : took evasive action
Consequence	faa : reviewed incident with flight crew
Miss Distance	horizontal : 500 vertical : 500
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

ATC (ZBW) cleared us to cross 082/27 DME of orw at 11000 ft and 250 KTS. At approximately 12 DME, TCASII indicated target in front of us and near our altitude. We passed under a bizjet light transport by about 500 ft. Made controled left turn to avoid the light transport. When on ground, contacted ZBW. They claim that light transport was VFR 12500 ft and in contact with ZBW. ATC controller was very busy at the time, but was in radio contact with both aircraft.

Original NASA ASRS Text

Title: MLG HAS TCASII WARNING ON DSCNT.

Narrative: ATC (ZBW) CLRED US TO CROSS 082/27 DME OF ORW AT 11000 FT AND 250 KTS. AT APPROX 12 DME, TCASII INDICATED TARGET IN FRONT OF US AND NEAR OUR ALT. WE PASSED UNDER A BIZJET LTT BY ABOUT 500 FT. MADE CTLED L TURN TO AVOID THE LTT. WHEN ON GND, CONTACTED ZBW. THEY CLAIM THAT LTT WAS VFR 12500 FT AND IN CONTACT WITH ZBW. ATC CTLR WAS VERY BUSY AT THE TIME, BUT WAS IN RADIO CONTACT WITH BOTH ACFT.

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.