Date: 201903
Local time of day: 0601-1200
Location: ZTL.ARTCC, GA
Aircraft: PA-31 Navajo/Chieftan/Mojave/T1040
Operator: Personal
Operating under: Part 91
Flight plan: IFR
Flight phase: Descent
Airspace: Class C BHM
ATC / advisory: Center ZTL
Second aircraft: Regional Jet 700 ER/LR (CRJ700)
Reporter organization: Government
Reporter function: Enroute
Reporter qualification: Air Traffic Control Fully Certified
Human factors: Situational Awareness; Communication Breakdown
Anomaly: ATC Issue All Types; Airspace Violation All Types; Conflict Airborne Conflict; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Air Traffic Control
When detected: In-flight
Result: Air Traffic Control Provided Assistance
Contributing factors: Human Factors
Primary problem: Human Factors

Narrative: This is an event between three aircraft; two that are normally in this area and one that is not. All three aircraft were required to be at 11;000 ft. at fixes that are approximately 10 miles apart. DIODE is one of these fixes and is used for BHM arrivals as a route and crossing restriction. WAMPM is a fix on the ZME/ZTL boundary used for crossing restrictions for HSV arrivals. This is a corner of airspace that is shared by ZTL sectors 4/5/12; and ZME Hamilton sector 12. Aircraft X was routed from direct BHM to NULLS BHM which is the preferred routing from the north into BHM. The aircraft was later rerouted DIODE BHM for reasons unknown. This aircraft would not have entered ZTL 04 if was kept on the preferred routing. Aircraft Y departing from PHL to BHM via DIODE BHM. There is an automated information transfer procedure between ZTL06/05 where the 06 controller descends the aircraft to FL240; and Sector 05 puts in an altitude of 11;000 feet or higher traffic permitting and hands the aircraft off to sector 04.  The Sector 05 Controller followed the procedure and entered 11;000 ft. in the data block. At some point; ZME [Sector] 12 pointed Aircraft X to ZTL 05 descending to 11;000 ft. and sector 05 approved the point out. Aircraft Y was still in the upper altitudes and had a faster ground speed but as the aircraft got lower the ground speed bled off and essentially was now tied at DIODE with Aircraft X.I was working Sector 04 and had the hand off on Aircraft Y; and Aircraft X was in hand off status when I recognized the potential conflict. Sector 06 switched the Aircraft Y to my frequency in which I had to stop the aircraft at 15;000 to ensure separation. Further I had to turn the Aircraft X to a 130 heading to sequence the aircraft into BHM in a safe and efficient manner.  Aircraft Z had to be stepped down to 11;000 ft. referenced both BHM inbounds as well. This safety event happened because Aircraft X should have never been put over the DIODE routing as it is not routine and requires coordination with an additional sector with not enough time to make a well thought out plan for separation. After speaking to my colleague at 05 it was stated that once it was realized there was a potential conflict; both aircraft were not on frequency to be able to do anything.  I had gone from never seeing this route and conflict before to twice in one session. The other resulting in a less complex and safe outcome.In the future I would like to have the aircraft on the preferred routing unless otherwise coordinated.  When other sectors are aware of potential conflict in a subsequent sector more proactive means of coordination for separation prior to accepting an AIT and/or point outs.




Synopsis: ZTL Center Controller reported a route conflict problem that he had never seen before to twice in one session.