Date: 201901
Local time of day: 0001-0600
Location: RFD.Airport, IL
Flight conditions: IMC
Weather elements / visibility: Fog; Cloudy; .25
Aircraft: B767 Undifferentiated or Other Model
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Cargo / Freight / Delivery
Flight phase: Taxi
ATC / advisory: Ground RFD
Second aircraft: Commercial Fixed Wing
Reporter organization: Air Carrier
Reporter function: First Officer; Pilot Not Flying
Reporter qualification: Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument
Human factors: Communication Breakdown
Anomaly: ATC Issue All Types; Conflict Ground Conflict; Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy; Ground Incursion Runway
Detector: Person Flight Crew
When detected: Taxi
Result: Air Traffic Control Provided Assistance; Flight Crew Requested ATC Assistance / Clarification
Contributing factors: Weather; Human Factors
Primary problem: Weather

Narrative: Event occurred taxing on taxiway F from our ramp to runway 7 for departure. On taxi the ground controller reported the new ATIS was current; which we had and I reported we had ATIS. The weather this morning was poor with reported visibility of 1/4 mile and a 200 feet indefinite ceiling. This ATIS also reported that CAT II/III operations were in effect. After this radio call the controller cleared us for takeoff on Runway 7. At this point we were still roughly 2;000 feet from the end of the runway and taxing slowly due to the poor visibility. We accepted the takeoff clearance but advised we would need time in position before takeoff (The temp was below 3C we needed to do the engine run up per company procedures). The controller responded with approved and advise when rolling. We figured there must not be any other traffic around but looking back on this the controller probably could not see our location on the airport due to the low vis and thought we were closer to the runway than we were.When reaching to preset the departure frequency I realized we were still on Ground and were cleared to takeoff on the ground control frequency (The same controller was working both) so I switched to tower. After switching to tower I heard our company aircraft; Aircraft Y; checking in on the ILS. It sounded like approach might have handed them over late. After this aircraft checked on the tower asked us if we had started rolling yet and we responded that we had not yet taken the runway. At this point we were between taxiway H and runway 7 on taxiway F. The tower controller once again asked us to verify that we were clear of the runway. We replied that we were clear of the runway and we were holding short. At this point we were holding short of Runway 7 on F and we could see on TCAS the inbound traffic was at 700 feet. The captain then asked me if we had entered the ILS Critical Area and neither one of us could remember passing the sign for one but we were not necessarily sure since we had been cleared for takeoff so early. Since vis was low with CAT II/III ops in effect; traffic on short final; and we were not sure if we were inside the ILS Critical Area or not (we were holding short of the runway) we decided to lean on the side of safety and reported to tower that we were inside the ILS critical area. The controller then instructed our company aircraft to go around; which they did. After they went around we were issued a new takeoff clearance and time in position to do our run up. We departed and completed our flight without any problems.After we departed we studied the jepp charts and could not find a ILS hold line depicted at RFD. Upon arrival [at our destination] we called RFD Tower on the phone and asked to clarify. The controller working our departure had already gone off duty but the controller we spoke to told us that the ILS Critical Area for Runway 7 was co-located with the hold short line and that we had not entered into the ILS Critical Area. He thanked us for taking a proactive approach to safety and said there were no issues. Looking back it seems we caused our company aircraft to unnecessarily go-around by erroneously reporting inside the ILS Critical Area. This was not intentional but since we were in doubt we leaned on the side of safety.




Synopsis: B767 First Officer reported low visibility and communications breakdown between flight crew and ATC resulted in ground conflict.