During the previous decades of organized oceanic operations, hundreds of navigation errors have been recorded. The vast majority of those errors have been flight crew-induced during initialization or in the course of updating while en route. A time-proven manner of avoidance of such crew-induced nav errors is to double-check all FMS initial and updated position entries by both pilots.
When an oceanic clearance is received, the flight crew should plot the waypoints on an oceanic plotting chart to ensure the coordinates received in the clearance match the coordinates that were programmed into the FMS. If there are any revisions to the flight plan, they will be entered in the correct position on the master flight plan and the old waypoints crossed out. An initial plot may take place, prior to departure, that represents the requested oceanic clearance. Once the clearance is received, as is often the case when traveling eastbound from the U.S., a second plot should be made.
As soon as practical after departure, one crewmember, typically the pilot monitoring (PM), should record the actual departure time on the master flight plan. This allows an accurate estimate to a gateway that may be fast approaching (examples: westbound out of London or Glasgow) and to have an accurate ETA to the destination. The estimate provided by the FMS may not initially be as accurate as the crew would like. It also will not necessarily provide an accurate ETA to an FIR boundary or initial track entry point during climb-out should the controlling agency request an estimated time of arrival at a particular fix along the flight routing.
In addition to the time to each fix along the flight plan, the crew should have an estimate of how much fuel will remain at each fix. Before takeoff the PM should record the total fuel load on the master flight plan and in parallel with listing each waypoint's ETA, the PM should note the estimate of the total fuel remaining at each fix.
Passing the oceanic gateway outbound, the crew should perform a gross-error check to ensure the long-range nav equipment is performing properly. This is accomplished by flying directly over the gateway, if practicable, and verifying that the aircraft is on the proper outbound course. Short-range navigation facilities may be monitored and compared to detect any deviations. This will help to detect any errors in the position updates since departure.
When approaching each waypoint, the crew should review the master flight plan and record all pertinent information, such as the fuel remaining and elapsed time. Also it is important to check that the present and following waypoint are in accordance with the clearance that was received by ATC. Overhead each waypoint, the crew should ensure that the aircraft turns in the proper direction and that the heading and mileage conform to the master flight plan estimates.
Once passing an en route waypoint in any non-radar environment it is important that the crew make a position report as soon as possible. Each cardinal clock position, on the hour, quarter past, half past and three-quarters past the hour, diligent navigational discipline dictates that the crew plots the actual position of the aircraft using the FMS/GPS coordinates to determine if they are on course and within the tolerances of the oceanic procedures. Each mark should fall directly on the plotting charts route directory that was drawn by the crew, prior to entering the oceanic airspace.
At the inbound gateway, the crew should cross-check VOR/DME positioning if available but continue to navigate using the FMS/GPS. In the event of a contingency, the crew will immediately notify ATC to inform them of the situation and, if required, request a revised clearance. A clearance should be received before any action is taken to change altitude or the route of flight. If ATC cannot be notified, the crew should broadcast their request on 121.5 until a clearance is received.
If one long-range navigation system fails before takeoff, the crew should consider the following options:
Delaying the departure until the system is repaired, or