HS125 captain reported an near midair collision with a DA20 in the vicinity of bdr.

Attributes
ACN	1466176
Time
Date	201707
Local Time Of Day	0601-1200
Place
Locale Reference	BDR.Airport
State Reference	NY
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	BAe 125 Series 800
Operating Under FAR Part	Part 135
Flight Phase	Cruise
Route In Use	Direct
Flight Plan	IFR
Aircraft 2
Make Model Name	DA20-A1 Katana
Operating Under FAR Part	Part 91
Flight Phase	Cruise
Person 1
Function	Captain
Qualification	Flight Crew Air Transport Pilot (ATP) Flight Crew Flight Instructor
Experience	Flight Crew Last 90 Days 47 Flight Crew Total 9000 Flight Crew Type 5630
Events
Anomaly	Conflict NMAC
Miss Distance	Horizontal 100 Vertical 0

Narrative:

While at 4000 ft we just passed bdr VOR headed northwest to rymes intersection and had to make evasive maneuvers to avoid a collision with a katana aircraft headed southwest bound also at 4000 ft. The meteorological conditions were 5 mi visibility and a scattered to broken layer at 3000 ft. The katana was white without its transponder operating and no radio communications with ATC. ATC didn't have any target appear on their screen either. TCAS didn't show a target nor did it alert us to the aircraft. A turn was employed to keep us away from the katana as it passed within 100 ft of our wing.

Original NASA ASRS Text

Title: HS125 Captain reported an NMAC with a DA20 in the vicinity of BDR.

Narrative: While at 4000 ft we just passed BDR VOR headed northwest to RYMES intersection and had to make evasive maneuvers to avoid a collision with a Katana aircraft headed southwest bound also at 4000 ft. The meteorological conditions were 5 mi visibility and a scattered to broken layer at 3000 ft. The Katana was white without its transponder operating and no radio communications with ATC. ATC didn't have any target appear on their screen either. TCAS didn't show a target nor did it alert us to the aircraft. A turn was employed to keep us away from the Katana as it passed within 100 ft of our wing.

Data retrieved from NASA's ASRS site 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.