ERJ170 captain reported responding to an RA while being vectored for an approach in marginal weather...

Attributes
ACN	1377947
Time
Date	201608
Local Time Of Day	1201-1800
Place
Locale Reference	ZZZ.TRACON
State Reference	US
Environment
Flight Conditions	Mixed
Light	Daylight
Aircraft 1
Make Model Name	EMB ERJ 170/175 ER/LR
Operating Under FAR Part	Part 121
Flight Phase	Descent
Flight Plan	IFR
Person 1
Function	Captain Pilot Not Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Person 2
Function	First Officer Pilot Flying
Experience	Flight Crew Type 400
Events
Anomaly	ATC Issue All Types Conflict NMAC Deviation - Procedural Clearance
Miss Distance	Horizontal 100 Vertical 400

Narrative:

I was the pilot monitoring with the first officer the pilot flying. We noticed a target on our TCAS 500 feet below us and a couple of miles off to the right of our course. The cloud layer was scattered to broken at our altitude; and we were in and out of IMC. At this point we were given a vector off the arrival to a heading of 050 and a descent to 2;100 feet; which was in the direction of the traffic. At the same time; we received a resolution advisory telling us to adjust vertical track. Immediately the TCAS now showed the target now above us; and the RA dictated us to adjust vs. At that point we saw the GA aircraft. The aircraft was supposed to be maintaining VFR. The aircraft passed above us; clearing us by what could not have been more than more than 300-400 feet. I believe the first officer's response to the RA was appropriate to the directions on his pfd; although his initial response might have been slightly delayed. This delay was momentary and I instructed him to 'follow the guidance' or something to that effect. The event only lasted a couple of seconds.

Original NASA ASRS Text

Title: ERJ170 Captain reported responding to an RA while being vectored for an approach in marginal weather conditions. Crew reported passing below a GA aircraft by about 400 feet.

Narrative: I was the pilot monitoring with the First Officer the pilot flying. We noticed a target on our TCAS 500 feet below us and a couple of miles off to the right of our course. The cloud layer was scattered to broken at our altitude; and we were in and out of IMC. At this point we were given a vector off the arrival to a heading of 050 and a descent to 2;100 feet; which was in the direction of the traffic. At the same time; we received a resolution advisory telling us to adjust vertical track. Immediately the TCAS now showed the target now above us; and the RA dictated us to adjust VS. At that point we saw the GA aircraft. The aircraft was supposed to be maintaining VFR. The aircraft passed above us; clearing us by what could not have been more than more than 300-400 feet. I believe the First Officer's response to the RA was appropriate to the directions on his PFD; although his initial response might have been slightly delayed. This delay was momentary and I instructed him to 'follow the guidance' or something to that effect. The event only lasted a couple of seconds.

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.

ERJ170 captain reported responding to an RA while being vectored for an approach in marginal weather conditions. Crew reported passing below a GA aircraft by about 400 feet.