DHC8 advises of evasive TCASII maneuver due to conflicting, untracked aircraft.

Attributes
ACN	451735
Time
Date	199910
Day	Thu
Local Time Of Day	1201 To 1800
Place
State Reference	PA
Altitude	msl bound lower : 9200 msl bound upper : 10000
Environment
Flight Conditions	VMC
Light	Dusk
Aircraft 1
Controlling Facilities	artcc : zny.artcc
Operator	common carrier : air carrier
Make Model Name	Dash 8 Series Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	cruise : level
Flight Plan	IFR
Aircraft 2
Controlling Facilities	artcc : zny.artcc
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Operating Under FAR Part	Part 91
Flight Phase	cruise : level
Person 1
Affiliation	government : faa
Function	controller : radar
Experience	controller non radar : 3 controller radar : 15
ASRS Report	451735
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	altitude deviation : excursion from assigned altitude conflict : airborne critical
Independent Detector	aircraft equipment : tcas other flight crewa
Miss Distance	vertical : 200
Supplementary
Problem Areas	Flight Crew Human Performance Airspace Structure
Primary Problem	Flight Crew Human Performance

Narrative:

I was the radar controller at sector 92, ZNY, when air carrier X reported that he was responding to a TCASII RA and descending. I did not see the other aircraft (Y) who was VFR until after they passed each other. Air carrier X said they had to descend to 9200 ft from 10000 ft to avoid the other aircraft.

Original NASA ASRS Text

Title: DHC8 ADVISES OF EVASIVE TCASII MANEUVER DUE TO CONFLICTING, UNTRACKED ACFT.

Narrative: I WAS THE RADAR CTLR AT SECTOR 92, ZNY, WHEN ACR X RPTED THAT HE WAS RESPONDING TO A TCASII RA AND DSNDING. I DID NOT SEE THE OTHER ACFT (Y) WHO WAS VFR UNTIL AFTER THEY PASSED EACH OTHER. ACR X SAID THEY HAD TO DSND TO 9200 FT FROM 10000 FT TO AVOID THE OTHER 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.