Date: 201708
Local time of day: 0601-1200
Location: SCT.TRACON, CA
Light: Daylight
Aircraft: Widebody; Low Wing; 2 Turbojet Eng
Operator: Air Carrier
Operating under: Part 129
Flight plan: IFR
Mission: Passenger
Flight phase: Descent
Airspace: Class B LAX
ATC / advisory: TRACON SCT
Reporter organization: Government
Reporter function: Approach
Reporter qualification: Air Traffic Control Fully Certified
Human factors: Confusion; Human-Machine Interface
Anomaly: ATC Issue All Types; Airspace Violation All Types; Deviation / Discrepancy - Procedural Other / Unknown
Detector: Person Air Traffic Control
When detected: In-flight
Result: Air Traffic Control Provided Assistance; Air Traffic Control Separated Traffic
Contributing factors: Airspace Structure; ATC Equipment / Nav Facility / Buildings; Procedure
Primary problem: ATC Equipment / Nav Facility / Buildings

Narrative: Aircraft X called my frequency descending on the OLAAA ONE arrival. I had no data block and no information on that aircraft. When I clicked on several limited data blocks around and in my airspace I realized that Aircraft X was an aircraft I was supposed to be talking to over OCN VOR. The aircraft was landing LAX. I then called ZLA thinking that they had made a simple mistake and switched him and forgot to initiate a handoff to me. When I looked at the data block it was on an 'E' tag and it had a 'C' in the hand off space of the data tag. As if the 'E' sector was handing off the aircraft to the center. ZLA controller said that he shows that I took the hand off and was attempting to handoff the aircraft off back to ZLA. I asked the controller to try and take the hand off and reflash it back to me. He informed me that he was able to take the handoff but unable to initiate a hand off to my sector. I then did a multi-function on the tag and was able to get control of the data tag to initiate a hand off to the next sector downy. The entire time in my sky it was on a 'C' tag and once the next controller took radar on the aircraft it reverted back to a 'C' tag as if the next sector did not take the handoff. This was a very serious automation issue. It could have created a very bad situation. The data block was limited and I did not see the airplane until it checked on my frequency and I started investigating. We usually have several aircraft over OCN VOR at the same altitude as the LAX arrivals are descending to on the OLAAA arrival. What if the center had forgotten to switch the aircraft? What if the aircraft went nordo. What if I was busy and missed the limited data block in my scan. We also have SAN arrivals that are at 13000 ft that can pass very close to OCN VOR creating a built in conflict with the OLAAA arrivals. If I had a SAN arrival that was north of their usual flight path it would have conflicted with Aircraft X heavy and could have been a potential NMAC; collision or at the very least a loss of standard separation. This was no one's fault. It was an automation issue. And if all the holes in the Swiss cheese had lined up things could have been much worse.




Synopsis: SCT TRACON Controller reported an aircraft checked in on the frequency that had not been handed off by Center due to computer issues.