A320
Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 167; Flight Crew Total 3348; Flight Crew Type 647
Confusion
Aircraft Equipment Problem Less Severe; Conflict Airborne Conflict; Deviation - Altitude Excursion From Assigned Altitude
Flight Crew Took Evasive Action; Flight Crew FLC complied w / Automation / Advisory; Flight Crew Requested ATC Assistance / Clarification; General Maintenance Action
Aircraft
The aircraft was in cruise at FL360 in clear conditions. I noticed a message on the ND (Navigation Display) that said 'decrease range TCAS.' When I decreased the range on the ND the TCAS showed a TA in yellow. The aircraft was at our altitude climbing very slowly. The target changed to a descend RA. The FO (First Officer) and I followed SOP and complied with the RA. I notified Center that we were deviating from our clearance due to an RA. We descended about 200 feet when I visually acquired the aircraft flying over us. At this point the target was 1000 feet above us according to the TCAS display. When we were clear of conflict; we climbed back to our previously assigned clearance and notified ATC. There were no aural warnings at all from the TCAS system. When we arrived [at our destination]; we wrote up the TCAS. Maintenance repaired the system and it tested good with the 'TCAS system test OK' aural message.
We were level at FL360; approximately 30-40nm SE of ZZZ VOR; on a direct course [along our route]. Aircraft Y received a clearance to climb to FL370. I am unsure of their starting altitude. The CA (Captain) first saw the TCAS icon indicating a RA (red square) on the ND (Navigation Display) and brought it to my attention. It showed Aircraft Y level at FL360; head on with our track at our altitude. Unbeknownst to us; a TCAS circuit breaker had tripped prior to this event; causing it to not generate any aural warnings for traffic. It took both of us a moment or two to process what was happening due to no aural alerts. I immediately executed the TCAS RA escape maneuver and initiated a shallow descent per the green VSI indications. We descended approximately 200 feet and Aircraft Y executed a rapid climb. We cleared each other by 1100 feet as we crossed each other. The controller implied that Aircraft Y had overly delayed their climb to FL370. I queried ATC about the clearance Aircraft Y had and received no response; as if the incident never happened. Once at the gate; we called MX (maintenance) and they noticed the circuit breaker that tripped after we left [our departure airport].
A320 flight crew reported a TCAS malfunction during an airborne conflict situation.