Date: 201208
Local time of day: 1201-1800
Location: ZBW.ARTCC, NH
Aircraft: Commercial Fixed Wing
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Flight phase: Cruise
Airspace: Class A ZBW
ATC / advisory: Center ZBW
Second aircraft: Any Unknown or Unlisted Aircraft Manufacturer
Reporter organization: Government
Reporter function: Enroute
Reporter qualification: Air Traffic Control Fully Certified
Human factors: Workload; Situational Awareness
Anomaly: ATC Issue All Types; Conflict Airborne Conflict
Detector: Person Air Traffic Control
Result: General None Reported / Taken
Contributing factors: Airspace Structure; Human Factors; Procedure; Staffing
Primary problem: Airspace Structure

Narrative: I was working R09. It was a bad weather day; there were many reroutes to areas south of the New York area. Sectors 08 and 09 were split off. Air Carrier X was in level flight just inside the northeast corner of my sector headed northwest bound to MSP at FL380. Sector 08 was busy working reroutes to PHL; DCA; IAD and BWI. I took two point outs on aircraft at FL380 and FL360; I cannot remember the call signs and I think both aircraft were overseas arrivals to PHL. RA08 called me with the point outs and I referenced traffic and said; 'This guy should be flashing at you anyway.' RA08 said something like; 'we'll be under him' and Air Carrier X's hand off to 08 was taken. I was focusing on aircraft in the southwest part of my sector. I did not notice that 08's aircraft at FL380 had slowly begun to descend until there was approximately 8 miles between my Air Carrier X and Sector 08's. I yelled across the isle asking 08 if that aircraft was hustling down. I turned my aircraft 30R thinking it would be enough especially with an expeditious decent. I don't think it worked. Sectors 08 and 09 were split off that morning after the stand up. On break; before this event; I asked the CIC during the stand up why 08 and 09 were split off so early. There was no volume then to justify the split. The CIC told me that the FLM came back after stand up and said he was told to split 08 and 09; I think it was in preparation for reroutes and bad weather. Eight and nine remained split all morning. I think one element to this event was the unusual complexity that was introduce because of the reroutes and our SOP with those aircraft along with the added complexity of working more constraining airspace. Sectors 08 and 09 were never recombined that morning because the reroutes caused for spurts of volume according to the Traffic Situation Display (TSD). In the past 08 and 09 have been combined; the TSD showed a 'red' sector; and the OM called and ordered it split off. The spurts shown on the TSD were not really spurts but shared aircraft between 08 and 09; so if the sectors were combined; as is the usual practice; the TSD would show a smaller number than simply adding the two numbers. A good time for 08 and 09 to be split is when there is a high amount of volume and low complexity. However; when there is a high amount of complexity and anything higher than moderate volume in 08 and 09; it is a detriment to have it split off because the airspace becomes constrictive. The decision to split these sectors should rest on the shoulders of the FLM and the controllers working the sector. I also think it should be considered to redraw 08 and 09 with the purpose to ease complexity not volume.




Synopsis: ZBW Controller indicated a probable loss of separation event noting facility sector combination protocols were contributory to this event; adding combination decisions should be made at the sector level.