Giv first officer reported not receiving a TA but an RA and descending to clear the RA.

Attributes
ACN	1668840
Time
Date	201907
Local Time Of Day	1801-2400
Place
Locale Reference	TEB.Airport
State Reference	NJ
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	Gulfstream IV / G350 / G450
Operating Under FAR Part	Part 91
Flight Phase	Initial Approach
Route In Use	Other ILS 19
Flight Plan	IFR
Person 1
Function	Dispatcher First Officer Pilot Flying
Qualification	Flight Crew Instrument Flight Crew Flight Instructor Flight Crew Air Transport Pilot (ATP) Flight Crew Multiengine
Experience	Flight Crew Total 2200 Flight Crew Type 600
Events
Anomaly	Conflict NMAC
Miss Distance	Vertical 200

Narrative:

During our ILS approach to runway 19 at teb we had an immediate RA. There was never any TA prior to the RA. We were instructed to proceed direct unvil and to maintain 2000 ft until established on the localizer; and we were cleared for the ILS 19 into teb. We were at 2000 ft; established on green needles; waiting for the glideslope to come in. All of a sudden; the RA announced descend; descend now and commanded a descent on the pfd (primary flight display). I immediately turned the autopilot off and followed the RA. We descended approximately 300 ft and stayed there until clear of conflict announced. By then; the glideslope was coming alive and we continued on the approach. We notified tower; and they asked a few questions both in the air and on the ground. They informed us that the traffic on their radar was showing 2500 ft. When the RA went off; it showed them at 200 ft above us. In the end; everyone was safe and no further action transpired. There was never a TA advising 'traffic; traffic' before the RA commanded a descent. This is a prime example of how even in VFR conditions; it is imperative to keep a sharp lookout.

Original NASA ASRS Text

Title: GIV First Officer reported not receiving a TA but an RA and descending to clear the RA.

Narrative: During our ILS approach to Runway 19 at TEB we had an immediate RA. There was never any TA prior to the RA. We were instructed to proceed direct UNVIL and to maintain 2000 ft until established on the LOC; and we were cleared for the ILS 19 into TEB. We were at 2000 ft; established on green needles; waiting for the glideslope to come in. All of a sudden; the RA announced descend; descend now and commanded a descent on the PFD (Primary Flight Display). I immediately turned the autopilot off and followed the RA. We descended approximately 300 ft and stayed there until clear of conflict announced. By then; the glideslope was coming alive and we continued on the approach. We notified Tower; and they asked a few questions both in the air and on the ground. They informed us that the traffic on their radar was showing 2500 ft. When the RA went off; it showed them at 200 ft above us. In the end; everyone was safe and no further action transpired. There was never a TA advising 'Traffic; Traffic' before the RA commanded a descent. This is a prime example of how even in VFR conditions; it is imperative to keep a sharp lookout.

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.