A pvd TRACON controller reported of a loss of separation when an IFR aircraft reacting to an RA desc...

Narrative:

I had just assumed the radar position in which prior training had occurred. As a result of this training I believe the some aircraft were out of an efficient/good position for the approach sequence. I attempted to fix this situation which contributed to complexity. I was working multiple sectors/frequency in which frequency congestion was apparent with aircraft stepping on one another. Aircraft Y; VFR requested a practice approach. I advised the aircraft to expect vectors for the sequence as he was going to be delayed slightly due to other inbound traffic. I assigned aircraft Y a vector west for the final and restricted his altitude at or below 2;500. The aircraft was level and 2;500 and never deviated from that altitude. Inbound from the west was aircraft X; IFR. Aircraft X was issued a heading to parallel final due to slower aircraft on the approach; and was issued a decent to 3;000 from 5;000. Aircraft X leveled at 3;000 for a few miles and I issued a turn for a box pattern to base. Aircraft X level at 3;000 and aircraft Y level and restricted at or below 2;500 appeared to be converging and traffic was issued to aircraft X. At approximately 1 mile apart aircraft X started descending and advised they were responding to an RA. This response to the RA caused a lack of separation standards (loss) and created a real collision hazard. There was no other traffic in the immediate area.it is my understanding that certain company policies require pilot action with regards to a TCAS ras however in this instance it caused a potential collision that was otherwise a controlled and safe operation. A review of airline TCAS policies and or software upgrade to TCAS systems may prevent this hazard in the future.

Original NASA ASRS Text

Title: A PVD TRACON Controller reported of a loss of separation when an IFR aircraft reacting to an RA descends into the altitude structure of a VFR aircraft. The Controller would like a review of airline TCAS policies and/or a software update to the TCAS System.

Narrative: I had just assumed the radar position in which prior training had occurred. As a result of this training I believe the some aircraft were out of an efficient/good position for the approach sequence. I attempted to fix this situation which contributed to complexity. I was working multiple sectors/frequency in which frequency congestion was apparent with aircraft stepping on one another. Aircraft Y; VFR requested a practice approach. I advised the aircraft to expect vectors for the sequence as he was going to be delayed slightly due to other inbound traffic. I assigned Aircraft Y a vector west for the final and restricted his altitude at or below 2;500. The aircraft was level and 2;500 and never deviated from that altitude. Inbound from the west was Aircraft X; IFR. Aircraft X was issued a heading to parallel final due to slower aircraft on the approach; and was issued a decent to 3;000 from 5;000. Aircraft X leveled at 3;000 for a few miles and I issued a turn for a box pattern to base. Aircraft X level at 3;000 and Aircraft Y level and restricted at or below 2;500 appeared to be converging and traffic was issued to Aircraft X. At approximately 1 mile apart Aircraft X started descending and advised they were responding to an RA. This response to the RA caused a Lack Of Separation Standards (LOSS) and created a real collision hazard. There was no other traffic in the immediate area.It is my understanding that certain company policies require pilot action with regards to a TCAS RAs however in this instance it caused a potential collision that was otherwise a controlled and safe operation. A review of airline TCAS policies and or software upgrade to TCAS systems may prevent this hazard in the future.

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.

Attributes
ACN	1297356
Time
Date	201509
Local Time Of Day	1201-1800
Place
Locale Reference	PVD.TRACON
State Reference	RI
Environment
Light	Daylight
Aircraft 1
Make Model Name	Large Transport Low Wing 2 Turbojet Eng
Operating Under FAR Part	Part 121
Flight Phase	Final Approach
Route In Use	Vectors
Flight Plan	IFR
Aircraft 2
Make Model Name	Small Aircraft
Flight Phase	Final Approach
Route In Use	Vectors
Flight Plan	VFR
Person 1
Function	Approach
Qualification	Air Traffic Control Fully Certified
Experience	Air Traffic Control Time Certified In Pos 1 (yrs) 5
Events
Anomaly	ATC Issue All Types Conflict Airborne Conflict Deviation - Altitude Excursion From Assigned Altitude Deviation - Procedural Clearance Deviation - Procedural Published Material / Policy

A pvd TRACON controller reported of a loss of separation when an IFR aircraft reacting to an RA descends into the altitude structure of a VFR aircraft. The controller would like a review of airline TCAS policies and/or a software update to the TCAS system.