Date: 202012
Local time of day: 1801-2400
Location: CLT.TRACON, NC
Flight conditions: IMC
Weather elements / visibility: Rain; Turbulence
Light: Night
Aircraft: Commercial Fixed Wing
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Descent
Airspace: Class E ZTL
ATC / advisory: TRACON CLT
Second aircraft: Any Unknown or Unlisted Aircraft Manufacturer
Reporter organization: Air Carrier
Reporter function: First Officer; Pilot Flying
Reporter qualification: Flight Crew Instrument; Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP)
Human factors: Time Pressure; Workload; Distraction; Human-Machine Interface; Situational Awareness
Anomaly: ATC Issue All Types; Conflict Airborne Conflict; Inflight Event / Encounter Weather / Turbulence
Detector: Automation Aircraft TA; Automation Aircraft RA; Person Flight Crew
Result: Air Traffic Control Issued New Clearance; Flight Crew Took Evasive Action; Flight Crew Requested ATC Assistance / Clarification; Flight Crew Returned To Clearance
Contributing factors: Chart Or Publication; Weather; Procedure; Human Factors
Primary problem: Procedure

Narrative: Upon descent on the RNAV arrival; the aircraft ahead advised 'moderate turbulence at 10;000 ft.… We as a crew evaluated the deviations options and concluded to stay on route and cross the next fix at 9;000 ft. The area north and south of course on the radar were shaded with darker colors. The current inflight night visibility was zero with moderate to heavy rain lightning and St Elmo's fire. Upon crossing the fix we begin to encounter moderate turbulence. The autopilot was engaged; 250 kts. speed selected. After passing the fix and right about when the smart turn over another fix began we received an immediate CLIMB RESOLUTION ADVISORY and a RED traffic appeared on the Multi-Function Display (MFD) in the 11 o'clock position.I; the Pilot Flying; began the TCAS TA/RA actions and call-outs disconnecting the autopilot; complying with the RA climb instructions. The Captain turned off the Flight Directors as per company procedures. Due to moderate turbulence the aircraft began to rapidly slow below the selected 250 kts.; so I; the Pilot Flying; selected TOGA (Take Off/Go Around) to equalize the descending energy and avoid a stall or near stall condition. With the lack of Flight Director (FD) lateral guidance the MFD became primary for lateral guidance for the turn over the fix; the red threat traffic appeared between us and turning left to rejoin the arrival. As we began to level off and reestablish vertical and lateral guidance ATC queried us. The Captain; who was Pilot Monitoring; was tasked with selecting the Flight Directors ON and selecting the desired modes to return us to course and altitude in a rather bumpy erratic flight condition. I; the Pilot Flying; with hands on a push to talk advised ATC of complying with a TCAS RA. As we began to turn back to course the previous red threat traffic reappeared yellow and a 'TRAFFIC; TRAFFIC' was heard; so we remained leveled off and slow turned towards the course. After establishing guidance; and positively managing the aircraft's speed and energy we began a turn towards the next fix. We as a crew were task saturated controlling the aircraft in moderate turbulence and complying with the TCAS RA and were merely queried by ATC; never advised of traffic by ATC or given any lateral guidance after stating we were complying with a TCAS RA. It was only several moments after we were reestablishing on course avoiding the traffic that ATC assigned a heading. Most disturbing during the irregularities of moderate turbulence; TCAS RA with traffic conflicting the turn; and turbulence induced energy state beyond authority of the auto thrust; ATC tries to immediately give us a phone number to call instead of any assistance in weather or traffic guidance.The portion of the RNAV arrival; during the event; has 6.5 miles to descend up to 2;000 ft.; slow 40 kts.; and smart turn 51 degrees; coupled with a very changing tailwind of 150 kts. at 20;000 [ft.] slowing to 36 kts. at 10;000 [ft.] and the aircraft's FMS plotting the deceleration to approach mode between fixes thus requiring manual speed selected management; it is a very busy part of the arrival.Casual factors were night with St. Elmo's fire; lightning causing a very dark outside and requiring bright instrumentation that is difficult for the eye to follow in moderate turbulence. Possible other factors of AUTO FLT FCU 1 FAIL immediately after the event. ATC was extremely busy. I think another big factor was ATC confusion of what we were experiencing; due to the fact we were both task saturated controlling the aircraft and avoiding a mid-air collision ATC communication became a lower priority. With reduced traffic separation ATC becomes an integral part of every flight; if the manuals would include 'advise ATC' as a step; and clear guidance on priority of traffic avoidance in relationship to lateral guidance and where it is seen or sourced this could help."




Synopsis: An Air Carrier pilot on an RNAV STAR at night in moderate turbulence and heavy rain reported taking evasive maneuvers to comply with a TCAS/RA advisory for conflicting traffic. They received no traffic advisory from ATC.