TRACON controller described a TCAS RA event when appropriate VFR/IFR separation was being applied an...

Narrative:

I was working combined sectors with the associated hand off positions. Traffic was moderate with a IFR citation on a vector northbound at 5;000 ft. I also had a VFR mooney on my frequency being vectored southbound. Traffic was issued to both aircraft more than once; letting each pilot know that the respective traffic was restricted above/below. When the citation; was approximately 1 mile from the mooney converging opposite direction; the citation told me he was responding to a RA and climbed approximately 200 ft; still within my airspace. No other aircraft were involved. Standard separation was never lost. Recommendation; both aircraft were in level flight separated by the required 500 ft separation. I don't understand why the TCAS-RA went off.

Original NASA ASRS Text

Title: TRACON Controller described a TCAS RA event when appropriate VFR/IFR separation was being applied and traffic information issued; the reporter questioning the TCAS equipment logic.

Narrative: I was working combined sectors with the associated hand off positions. Traffic was moderate with a IFR Citation on a vector northbound at 5;000 FT. I also had a VFR Mooney on my frequency being vectored southbound. Traffic was issued to both aircraft more than once; letting each pilot know that the respective traffic was restricted above/below. When the Citation; was approximately 1 mile from the Mooney converging opposite direction; the Citation told me he was responding to a RA and climbed approximately 200 FT; still within my airspace. No other aircraft were involved. Standard separation was never lost. Recommendation; both aircraft were in level flight separated by the required 500 FT separation. I don't understand why the TCAS-RA went off.

Data retrieved from NASA's ASRS site as of April 2012 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.

Attributes
ACN	944796
Time
Date	201104
Local Time Of Day	1801-2400
Place
Locale Reference	P50.TRACON
State Reference	AZ
Aircraft 1
Make Model Name	Citation X (C750)
Operating Under FAR Part	Part 91
Flight Phase	Cruise
Route In Use	Vectors
Flight Plan	IFR
Person 1
Function	Approach
Qualification	Air Traffic Control Fully Certified
Events
Anomaly	ATC Issue All Types Conflict Airborne Conflict

TRACON controller described a TCAS RA event when appropriate VFR/IFR separation was being applied and traffic information issued; the reporter questioning the TCAS equipment logic.