Date: 201202
Local time of day: 1801-2400
Location: ZZZ.Airport, US
Aircraft: Regional Jet 700 ER/LR (CRJ700)
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Flight phase: Cruise
Airspace: Class B ZZZ
ATC / advisory: TRACON ZZZ
Second aircraft: Regional Jet 200 ER/LR (CRJ200)
Reporter organization: Government
Reporter function: Approach
Reporter qualification: Air Traffic Control Fully Certified
Human factors: Training / Qualification; Confusion; Communication Breakdown
Anomaly: ATC Issue All Types; Conflict Airborne Conflict
Detector: Person Air Traffic Control
When detected: In-flight
Result: Air Traffic Control Issued New Clearance
Contributing factors: Procedure; Human Factors; ATC Equipment / Nav Facility / Buildings
Primary problem: Procedure

Narrative: While providing OJT we accepted the RADAR hand off on a CRJ2 from the S Sector over the western portion of our airspace; descending to 6;000 FT; our sector owns up to 5;000 FT. The CRJ2 was eastbound. We accepted the hand off on a CRJ7; from the Sector; over the eastern portion of our airspace. The CRJ7 was westbound at 6;000 FT. Neither aircraft checked on to our frequency. We continued working our arrivals; when a short time later we realized that the above aircraft were on opposite direction vectors; converging at the same altitude. We attempted to make contact with the aircraft; neither one responded. We told the S Controller that we weren't talking to either aircraft; and alerted him to the conflict. The S Controller stated that the aircraft was turning. After several seconds; we noticed that the aircraft were still converging; neither one turning. We again called the CRJ2; the aircraft which the S Controller stated that he had switched and got no response. I again told the S Controller that we weren't talking to the CRJ2 and told him to turn the CRJ7; as the aircraft were a conflict. I issued a turn and descent to the CRJ2 in the blind; which the aircraft didn't comply with. It seemed obvious to me that the CRJ2 was never on our frequency. We selected another frequency that is occasionally used for our sector; and still got no answer from the CRJ2. We attempted to reach the CRJ2 on 121.5 with no answer. The aircraft passed by each other; within about 2 miles at the same altitude. Only after the aircraft had passed; did another sector locate the CRJ2 on their frequency. We finally got both the CRJ2 and the CRJ7 on our frequency after the error had occurred. We then worked both aircraft into Runway XX without further incident. Recommendation; the S Controller should not vector aircraft head on; at the same altitude; hoping that the W Sector will descend one of them into the W's airspace. In this case; it is my opinion that either the S switched the CRJ2 to the wrong frequency; and/or the CRJ2 read back the wrong frequency. In either case; we (the W) were unable to resolve the conflict for the S because we weren't talking to either of the aircraft; both of which were still in the S's airspace. The S Controller should have used positive separation; in this case vertical; to ensure that this situation would not have happened. Additionally; after the error had occurred; there seemed to be some confusion in the RADAR room over which frequency we (the W) were using. We were using frequency standbys. This is what we'd been using for the 30 minutes prior to the incident. Management stated that we should be using another frequency; which we had never been informed we should be using. During the incident we tried the other frequency; to see if the CRJ2 was there; and he was not. There should never be confusion over which frequency a sector is using. A sector should use their standard frequency; unless an outage is posted in the SIA. The only outage that was posted was the standbys. We were briefed by the previous controller to use standbys; and so we did.




Synopsis: TRACON Controller providing OJT described an opposite direction conflict; reportedly due to the Controller's inability to communicate with either aircraft. Other information indicates the possibility of wrong standby frequency assignments.