Date: 201705
Local time of day: 1801-2400
Location: ZTL.ARTCC, GA
Light: Daylight
Aircraft: Large Transport; Low Wing; 2 Turbojet Eng
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Cruise
Airspace: Class A ZTL
ATC / advisory: Center ZTL
Second aircraft: Large Transport; Low Wing; 2 Turbojet Eng
Reporter organization: Government
Reporter function: Instructor; Enroute
Reporter qualification: Air Traffic Control Fully Certified
Human factors: Distraction; Situational Awareness; Training / Qualification
Second reporter function: Handoff / Assist; Enroute
Anomaly: ATC Issue All Types; Airspace Violation All Types; Conflict Airborne Conflict; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural FAR; Inflight Event / Encounter Weather / Turbulence
Detector: Automation Aircraft RA; Automation Aircraft TA; Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Issued New Clearance; Flight Crew Took Evasive Action
Contributing factors: Human Factors; Environment - Non Weather Related; Procedure
Primary problem: Human Factors

Narrative: I was relieving a controller on R06 with the intent to train an R side trainee. Aircraft landing ATL were entering hold and only the far eastern edge of sector was available due to weather. The previous controller issued holding to numerous aircraft on a non-published holding pattern because weather would not allow holding at common fixes. Aircraft X was unable to hold with other aircraft because it was non RNAV. The aircraft were holding where they would need point out to the adjacent sector (37). Before I felt comfortable giving the sector to the trainee; I felt the sector needed to be cleaned up and more orderly. I issued clearances while the trainee updated the data blocks and the relieving controller slide to D-side. I issued Aircraft X a descent from FL310 to FL240. I noticed flashing in the vicinity but it was with other aircraft not in my control. Without my noticing the change of two aircraft flashing due to multiple data blocks in the vicinity Aircraft X and Aircraft Y started flashing. Before I was able to observe and react; Aircraft Y stated they were responding to a TCAS at FL290 and climbing. Seconds later Aircraft X stated they were responding to a TCAS as well. Make sure the sector is safe and orderly by assuming responsibility.


Second narrative: Weather was covering most of the area. ATL was shut off due to weather at the airport. None of our holding patterns were usable so we had to give detailed holding instructions. I was going from the R-side to the D-side so that training could be accomplished. Aircraft X was on the RGM5 arrival and ended up holding at GQO. The OJTI (On the Job Training Instructor) took control of the sector to help get things set up for the trainee. Every aircraft had requests concerning the weather and know long the airport was going to be closed. We had one aircraft divert. The R-side descended Aircraft X to FL240 and the aircraft did not descend as fast as expected. Once we recognized the situation the aircraft was expedited and the other aircraft was turned to a 270 heading. I think both got a TCAS alert (but not sure). During this time I believe several aircraft may have needed to be pointed out to Sector 37 but this was not done. They had a data block on all of them. It would have been great if TMU had taken into account the weather and stopped all aircraft from entering the sector. I believe that Traffic management at Atlanta Center is left up to the controller on the sector and no planning is done; especially with weather.


Synopsis: ZTL Center Controllers reported a loss of separation during a Controller switch and briefing.