Date: 201707
Local time of day: 0001-0600
Location: EGGX.ARTCC, FO
Light: Daylight
Aircraft: Widebody; Low Wing; 2 Turbojet Eng
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Cruise
ATC / advisory: Center EGGX
Aircraft component: INS / IRS / IRU
Component problem: Failed
Reporter organization: Air Carrier
Reporter function: Pilot Not Flying; Captain; Check Pilot
Reporter qualification: Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Flight Instructor
Human factors: Communication Breakdown
Anomaly: Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural FAR; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Provided Assistance; Flight Crew Requested ATC Assistance / Clarification; Flight Crew Overcame Equipment Problem
Contributing factors: Manuals; Aircraft; Procedure
Primary problem: Procedure

Narrative: L IRS (Inertial Reference System) Fault indication while in Shanwick airspace over North Atlantic; 50 minutes prior to ETOPS entry. We advised our dispatcher of the problem; asked them to relay to maintenance and advise if it would affect our ETOPS routing. We then consulted our DDG (Dispatch Deviations Guide) with the help of on-board maintenance personnel. Unable to reset the system; we were told by maintenance to standby. 70 minutes later; after entering into ETOPS airspace we inquired as to what dispatch had come up with. We were asked to forward a position report and were told to possibly expect a reroute/ divert. At 25W we were then told by dispatch that if the failure occurred prior to our ETOPS entry point of 20W that we were illegal to enter. By this time we were inside ETOPS airspace. At 28W; 80 minutes after advising of the IRS Fault; we were given a company re-route that after plotting did not take us clear of ETOPS airspace. The route was 20w direct AVUTI. We petitioned ATC via ACARS and did not hear back; so decided to contact them via HF. We were asked at 32W if we could accept direct HOIST. After plotting once again we decided at 37W that it would be best to continue ahead as cleared by ATC since it was similar in line with what dispatch had advised. It was also similar distance to exit ETOPS airspace at that point as it would have been to divert north. We kept dispatch apprised of the changes and the flight landed safely without further issue. The issue was that with the IRS Fault; there was no language in the QRH/ETOPS manual to tell us to avoid ETOPS airspace with the given failure. Since it took 80 minutes for dispatch to get to us with a plan; we were unable to divert since no emergency condition existed. By the time we knew the inoperative navigational system would prevent ETOPS entry (DDG); we were already past the entry point. All effort was made to relay information and get dispatch and maintenance involved as soon as the problem occurred; knowing that ETOPS entry was 40 minutes ahead. Lack of timely reply from dispatch is cited as reason for ETOPS entry.




Synopsis: Captain of a large passenger turbojet reported experiencing a failure of one IRS system which inhibited their ability to enter ETOPS airspace.