World Air Ops | NAT | Doc 007 MNPS Guidance

Guidance concerning Air Navigation in and above the NAT MNPSA CHAPTER 14continue into the NAT MNPSA at FL310. Separation was immediately lost with a preceedingaircraft at that flight level.Crews are responsible for requesting and obtaining any domestic ATC clearance necessary to climb(or descend) to the initial flight level specified in their received Oceanic Clearance, prior to reachingthe oceanic boundary. While adjacent ACCs generally use their best endeavours to get an aircraft toit's oceanic level before the boundary, it must be recognized that entry into NAT MNPSA at thecleared oceanic level is entirely the responsibility of the crew. It does appear from the relativefrequency of this type of error that this is not widely understood. It should also be appreciated thatsuch requests must be made sufficiently early to allow the domestic ATC unit time torespond.f) An occasional error is to fly at one (uncleared) level and report at the (different) cleared level !e.g. the crew of a major airline reported at FL360 (the cleared level), all the way across theocean but were in fact flying at FL350!! They had been cleared to cross 40°W at FL360 andcorrectly entered the cleared level into the FMC but did not execute the command prior to40°W. During position reporting the aircraft level was reported by reference to the FMCaltitude hold box.Without SSR ATC must rely upon crew position report data to plan for the safe separation of alltraffic. If any such data is in error actual separations can be compromised.14.3 LATERAL NAVIGATION ERRORSMore Common Causes Of Lateral Navigation Errors14.3.1 The most common causes of GNEs, in approximate order of frequency, have been asfollows:a) having already inserted the filed flight plan route co-ordinates into the navigation computers, thecrew have been re-cleared by ATC, or have asked for and obtained a re-clearance, but have thenomitted to re-program the navigation system(s), amend the Master Document or update theplotting chart accordingly.b) a mistake of one degree of latitude has been made in inserting a forward waypoint. There seemsto be a greater tendency for this error to be made when a track, after passing through the samelatitude at several waypoints (e.g. 57°N 50°W, 57°N 40°W, 57°N 30°W) then changes by onedegree of latitude (e.g. 56°N 20°W). Other circumstances which can lead to this mistake beingmade include receiving a re-clearance in flight.c) the autopilot has been inadvertently left in the heading or de-coupled mode after avoidingweather, or left in the VOR position after leaving the last domestic airspace VOR. In somecases, the mistake has arisen during distraction caused by SELCAL or by some flight deckwarning indication.d) an error has arisen in the ATC Controller/Pilot communications loop, so that the controller andthe crew have had different understandings of the clearance. In some cases, the pilot has heardnot what was said, but what he/she was expecting to hear.NAT Doc 007 86 Edition 2010