A first officer notes that while on radar vectors they changed heading in response to a TCAS TA.

Attributes
ACN	714346
Time
Date	200610
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : lnk.tracon
State Reference	NE
Altitude	msl single value : 4000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : lnk.tracon
Operator	other
Make Model Name	Military
Operating Under FAR Part	Part 91
Flight Phase	descent : approach
Route In Use	arrival : on vectors
Flight Plan	IFR
Person 1
Affiliation	government : military
Function	flight crew : first officer
Qualification	pilot : private pilot : multi engine pilot : commercial pilot : instrument
Experience	flight time last 90 days : 70 flight time total : 400 flight time type : 750
ASRS Report	714346
Person 2
Affiliation	government : military
Function	flight crew : captain oversight : pic
Events
Anomaly	conflict : airborne less severe non adherence : clearance other spatial deviation
Independent Detector	other controllera
Resolutory Action	controller : issued advisory controller : issued new clearance
Supplementary
Problem Areas	ATC Human Performance Flight Crew Human Performance
Primary Problem	Ambiguous

Narrative:

I was in the right seat and not flying the aircraft at the time of the incident. We were north of the airfield at 4000 ft on vectors for the ILS 18 looking for the option back to radar. I think we were given a 035 degree heading and that is what I think I replied back to the controller. While on the heading; we noticed another aircraft below us at about 2 O'clock position and appeared to be climbing on a collision course. We turned right at 4000 ft to maintain safety of flight and avoid a collision. I informed the approach controller of our actions. He replied that if on a 355 degree heading the traffic was no factor. He then told us to turn right to 360 degrees. I found it odd to turn right to 360 degrees (nearly a 360 degree turn) and replied; left heading 360 degrees? He promptly corrected me and said right heading 360 degrees. I responded; right turn heading 360 degrees for a 'three sixty.' we then completed 2 additional approachs and the flight was over. I found our proximity to the other aircraft unusual for the terminal area. It was not until 3 hours after landing when the airfield manager called; that I realized the serious nature of the situation. We had deviated from a clearance (to avoid the other aircraft). Although we did have a TA warning; we could have asked the controller about the impending situation. Correct headings and altitudes are extremely important; especially in the terminal environment. If there is ever any question or confusion; ask the controller. If the situation permits; ask the controller to resolve a situation before deviating from a clearance and taking it into your own hands. In retrospect; we could have disrupted the controller's airspace when we deviated by moving ourselves away from the planned flight path. This type of situation can be prevented by being vigilant on the radios and using TCAS to anticipate situations and resolve them with ATC before they are perceived safety of flight issues.

Original NASA ASRS Text

Title: A FO NOTES THAT WHILE ON RADAR VECTORS THEY CHANGED HDG IN RESPONSE TO A TCAS TA.

Narrative: I WAS IN THE R SEAT AND NOT FLYING THE ACFT AT THE TIME OF THE INCIDENT. WE WERE N OF THE AIRFIELD AT 4000 FT ON VECTORS FOR THE ILS 18 LOOKING FOR THE OPTION BACK TO RADAR. I THINK WE WERE GIVEN A 035 DEG HDG AND THAT IS WHAT I THINK I REPLIED BACK TO THE CTLR. WHILE ON THE HDG; WE NOTICED ANOTHER ACFT BELOW US AT ABOUT 2 O'CLOCK POS AND APPEARED TO BE CLBING ON A COLLISION COURSE. WE TURNED R AT 4000 FT TO MAINTAIN SAFETY OF FLT AND AVOID A COLLISION. I INFORMED THE APCH CTLR OF OUR ACTIONS. HE REPLIED THAT IF ON A 355 DEG HDG THE TFC WAS NO FACTOR. HE THEN TOLD US TO TURN R TO 360 DEGS. I FOUND IT ODD TO TURN R TO 360 DEGS (NEARLY A 360 DEG TURN) AND REPLIED; L HDG 360 DEGS? HE PROMPTLY CORRECTED ME AND SAID R HDG 360 DEGS. I RESPONDED; R TURN HDG 360 DEGS FOR A 'THREE SIXTY.' WE THEN COMPLETED 2 ADDITIONAL APCHS AND THE FLT WAS OVER. I FOUND OUR PROX TO THE OTHER ACFT UNUSUAL FOR THE TERMINAL AREA. IT WAS NOT UNTIL 3 HRS AFTER LNDG WHEN THE AIRFIELD MGR CALLED; THAT I REALIZED THE SERIOUS NATURE OF THE SITUATION. WE HAD DEVIATED FROM A CLRNC (TO AVOID THE OTHER ACFT). ALTHOUGH WE DID HAVE A TA WARNING; WE COULD HAVE ASKED THE CTLR ABOUT THE IMPENDING SITUATION. CORRECT HDGS AND ALTS ARE EXTREMELY IMPORTANT; ESPECIALLY IN THE TERMINAL ENVIRONMENT. IF THERE IS EVER ANY QUESTION OR CONFUSION; ASK THE CTLR. IF THE SITUATION PERMITS; ASK THE CTLR TO RESOLVE A SITUATION BEFORE DEVIATING FROM A CLRNC AND TAKING IT INTO YOUR OWN HANDS. IN RETROSPECT; WE COULD HAVE DISRUPTED THE CTLR'S AIRSPACE WHEN WE DEVIATED BY MOVING OURSELVES AWAY FROM THE PLANNED FLT PATH. THIS TYPE OF SITUATION CAN BE PREVENTED BY BEING VIGILANT ON THE RADIOS AND USING TCAS TO ANTICIPATE SITUATIONS AND RESOLVE THEM WITH ATC BEFORE THEY ARE PERCEIVED SAFETY OF FLT ISSUES.

Data retrieved from NASA's ASRS site as of January 2009 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.