Date: 201511
Local time of day: 1201-1800
Location: ZNY.ARTCC, NY
Light: Daylight
Aircraft: B777 Undifferentiated or Other Model
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Cruise
Airspace: Special Use OCEANIC
ATC / advisory: Center ZNY
Second aircraft: B737 Undifferentiated or Other Model
Reporter organization: Government
Reporter function: Enroute; Oceanic
Human factors: Situational Awareness; Human-Machine Interface; Confusion
Second reporter function: Enroute; Oceanic
Anomaly: ATC Issue All Types; Conflict Airborne Conflict
Detector: Person Air Traffic Control
Result: Air Traffic Control Issued New Clearance; Air Traffic Control Separated Traffic
Contributing factors: Airspace Structure; ATC Equipment / Nav Facility / Buildings; Weather; Procedure
Primary problem: ATC Equipment / Nav Facility / Buildings

Narrative: I was working Oceanic Sectors; which are on the Advanced Technologies and Oceanic Procedures (ATOP) system.  The ATOP system is 100 percent reliant on the conflict probe for separation. I noticed Aircraft X at 33;000 feet approaching my airspace. Aircraft X's altitude box was outlined in magenta; which typically indicates a flight has not been coordinated inbound to the ATOP system.  This is highly irregular to have a magenta box on an aircraft depicted within the ATOP airspace.  Aircraft X was Automatic Dependent Surveillance (ADS) equipped; which; in my mind; gave his position substantial credibility.The other sector controller had just split out the sector.  We discussed the flight; and in his opinion the displayed position was likely accurate.  The flight was on a deviation; but I was not receiving any messages since I did not have track control.Sizing up my southbound Aircraft Y; which was still in an adjacent sector airspace; I judged there was not adequate separation between Aircraft X and Aircraft Y.  ATOP was not indicating the flights were in conflict; but even so; I had the adjacent sector move Aircraft Y to 34;000 feet.Once the other controller reestablished the data block on Aircraft X so that it no longer had the magenta box indicating a pre-coordinated status; I probed the Aircraft Y at the Aircraft X's altitude.The flights had zero minutes crossing.  ATOP never indicated there would be a loss of separation.Aircraft X deviated further south; creating more lateral separation between the flights.Separation was never lost because I changed Aircraft Y's altitude.The ADS reports should trigger a probe.Perhaps the circumstance where a flight is on a deviation that could prevent a flight from entering a radar volume should be re-examined by the ATOP team.  Presently; when the flight is projected to be within the radar volume; ATOP stops probing.  Here; the ADS reports clearly indicated the flight was not in the radar volume.


Second narrative: Aircraft X was deviating 100 miles left due to weather. During this time his Automatic Dependent Surveillance (ADS) was reporting his current position but always reporting the next fix on his route without updating its ETA at the fix. This ADS abnormality allowed Advanced Technologies and Oceanic Procedures (ATOP) to continually project the flight as going to the fix even though the aircraft was never even going into that sector. Eventually ATOP considered the flight to be within a different sector and moved the data block accordingly; leaving the aircraft in a different sector unprotected and without a profile.One change that could take place is to give ATOP the ability to use more or less of the data within an ADS report depending on the situation. This would allow ATOP to more accurately reflect the position of the aircraft not only in odd situations such as this but in day to day normality.


Synopsis: An ADS-B equipped aircraft in oceanic airspace was deviating for weather approximately 100 miles off course. The Advanced Technologies and Oceanic Procedures (ATOP) system is a radar Data processing system for ATC to use in Oceanic airspace where there is no radar coverage. It relies on Automatic Dependent Surveillance (ADS) equipped aircraft transmitting position reports and forecasts routes and possible conflictions. Due to the extensive deviation of this flight for weather the ATOP system was unable to accurately track the position and projected route of this aircraft. The controllers realized there may be an error in reporting and descended a different aircraft along the route. Once they verified an accurate position of the deviating aircraft they realized it would have been in confliction with the other aircraft which they had descended.