A C560 captain reported taking evasive action when in S46's airspace.

Attributes
ACN	599912
Time
Date	200311
Day	Thu
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : pae.airport
State Reference	WA
Altitude	msl bound lower : 4000 msl bound upper : 5000
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	tracon : s46.tracon
Operator	general aviation : corporate
Make Model Name	Citation Excel
Operating Under FAR Part	Part 91
Flight Phase	descent : approach
Route In Use	arrival : on vectors
Flight Plan	IFR
Aircraft 2
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Flight Phase	cruise : enroute altitude change
Person 1
Affiliation	company : corporate
Function	flight crew : captain oversight : pic
Qualification	pilot : cfi pilot : atp pilot : multi engine
Experience	flight time last 90 days : 119 flight time total : 5590 flight time type : 362
ASRS Report	599912
Person 2
Affiliation	company : corporate
Function	flight crew : first officer
Events
Anomaly	conflict : airborne critical
Independent Detector	aircraft equipment : tcas other flight crewa
Resolutory Action	flight crew : took evasive action
Miss Distance	horizontal : 1000 vertical : 500
Supplementary
Problem Areas	ATC Human Performance Airspace Structure Flight Crew Human Performance
Primary Problem	Airspace Structure

Narrative:

While being radar vectored, 10-12 mi northeast of pae, ATC (seattle approach) reported traffic at our 12 O'clock position and 10000 ft lower, but ATC was not talking to them. I noticed the target on our TCASII display at 1 O'clock position and 4 mi, indicating 300 ft below us and closing in. Both of us looked outside for the traffic but could not find lights against the city lights. As soon as our TCASII gave an RA climb warning, I responded and climbed 1000 ft. When clear of the conflict, we notified ATC of altitude deviation and returned to pae.

Original NASA ASRS Text

Title: A C560 CAPT RPTED TAKING EVASIVE ACTION WHEN IN S46'S AIRSPACE.

Narrative: WHILE BEING RADAR VECTORED, 10-12 MI NE OF PAE, ATC (SEATTLE APCH) RPTED TFC AT OUR 12 O'CLOCK POS AND 10000 FT LOWER, BUT ATC WAS NOT TALKING TO THEM. I NOTICED THE TARGET ON OUR TCASII DISPLAY AT 1 O'CLOCK POS AND 4 MI, INDICATING 300 FT BELOW US AND CLOSING IN. BOTH OF US LOOKED OUTSIDE FOR THE TFC BUT COULD NOT FIND LIGHTS AGAINST THE CITY LIGHTS. AS SOON AS OUR TCASII GAVE AN RA CLB WARNING, I RESPONDED AND CLBED 1000 FT. WHEN CLR OF THE CONFLICT, WE NOTIFIED ATC OF ALTDEV AND RETURNED TO PAE.

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.